JP2019128729A - Influence light source specification program, influence light source specification method, influence light source specification device and drawing processing program - Google Patents

Abstract

To specify a light source affecting a shading point when a bounding volume for each light source is set starting from the shading point in a three-dimensional virtual space.SOLUTION: An influence light source specification device comprises: an area shape determination part that determines a shape common to all light sources for a bounding volume that is set starting from a shading point and defines an influence range area to the shading point on the basis of a condition given to the shading point; an area size determination part that stochastically selects and determines a size of the bounding volume set for each light source from a plurality of candidates; and an intersection determination part that determines whether the bounding volume set for each light source has a position of the light source, and when the bounding volume has the light source, specifies the light source as a light source affecting the shading point.SELECTED DRAWING: Figure 2

Description

  At least one of the embodiments of the present invention is an influence light source specifying program for specifying a light source that affects a shading point when setting a bounding volume for each light source starting from the shading point in a three-dimensional virtual space, The present invention relates to an influence light source identification method, an influence light source identification device, and a drawing processing program.

  In recent years, in the field of graphics drawing, application of global illumination (global illumination) has been performed in order to perform more realistic graphic representation. Since the operation relating to the global illumination performs the operation in consideration of the optical paths from various light sources at one point, the amount of operation is enormous if the operation is to be performed for all the optical paths. In the field of real-time rendering, since it is necessary to perform computation in real time, there is a time limitation, and there is a problem that it is necessary to reduce the amount of computation while aiming at realistic graphics.

  Write culling is performed as a method for reducing the amount of computation. Light culling is a method in which the influence range of light from a light source is limited to a predetermined range in a three-dimensional virtual space, and the calculation amount is reduced by ignoring the influence of the light source at points outside the predetermined range. However, when performing light culling, if the influence range of the light from the light source is uniformly limited to a predetermined range, there is a problem that the drawing screen will be darkened due to the location where the light from the light source does not reach. there were.

  For example, Non-Patent Document 1 is cited as a disclosure of the contents that solve the problems of the light culling technique. This Non-Patent Document 1 discloses stochastic light culling that probabilistically changes the size of the bounding volume that determines the range of influence of light from the light source. Non-Patent Document 1 describes a virtual point light source (VPL: Virtual Point Light) used to express indirect illumination, where the VPL installation point is made of a material that performs specular reflection. Determining the range of influence Based on the fact that global illumination can be closer to reality by expressing the shape of the bounding volume with bounding ellipse rather than sphere, the crossing judgment method when adopting an ellipsoid for bounding volume is available. It is disclosed.

Stochastic Light Culling for VPLs on GGX Microsurfaces: Yusuke Tokuyoshi, Takahiro Harada: Computer Graphics Forum Volume 36, Issue 4, pages 55-63, July 2017 (http://onlinelibrary.wiley.com/doi/10.1111/cgf.13224/ abstract)

  FIG. 9 is an explanatory diagram showing a conventional concept when calculating the influence of a virtual point light source (VPL) on a shading point. FIG. 9 shows a conventional example in which the shape and size of the bounding volume are determined for each VPL employed in Non-Patent Document 1, and the size is determined by a probabilistic light culling technique. As shown in FIG. 9, the VPL is arranged on the wall surface where the light from the light source is reflected. If the material of the wall surface is a glossy surface at this time, the shape of the bounding volume set to the VPL is an ellipsoid. Is preferred. Since the size of the bounding volume of each VPL is determined by the probability from a plurality of size candidates, the size of the bounding volume for each VPL is different as shown in FIG. When a shading point is included in the VPL bounding volume set in this way, the calculation is performed by reflecting the influence from the VPL in the shading point drawing process.

  By the way, as shown in FIG. 9, when the light path of light source → wall surface → floor surface → viewpoint is traced, whether the light from the light source reaches the viewpoint depending on whether the wall surface and the floor surface are diffusing surfaces or glossy surfaces, respectively. Whether or not it changes. As shown in FIG. 9, when viewed statistically, in the case of the route of (1) light source → diffusion surface → diffusion surface → viewpoint and (2) the route of light source → glossy surface → diffusion surface → viewpoint The estimated value of the brightness related to the light from the light source reaching the viewpoint is close to the expected value, that is, the variance of the estimated value is small. However, in the case of the path of (3) light source → diffuse surface → gloss surface → viewpoint and (4) path of light source → gloss surface → gloss surface → viewpoint, the light from the light source is statistically viewed. The estimated value of brightness related to reaching the viewpoint is greatly different from the expected value, that is, the variance of the estimated value becomes large. In the case of high dispersion, there is a difference in the degree of light arrival for each drawing screen. Therefore, when multiple drawing screens are connected to create a moving image, the same drawing point may become brighter or darker. May cause an unpleasant image. That is, there is an unsuitable drawing scene in which the shape of the bounding volume is determined for each VPL employed in Non-Patent Document 1 and the size of the bounding volume is determined stochastically, resulting in high dispersion. Therefore, another method capable of achieving low dispersion has been desired.

  An object of at least one embodiment of the present invention is to provide an influential light source specifying program for specifying a light source that affects a shading point when a bounding volume is set for each light source starting from the shading point in a three-dimensional virtual space. An influence light source identification method and an influence light source identification device are provided.

  According to a non-limiting viewpoint, the influence light source identification program according to an embodiment of the present invention determines whether light from a light source including a virtual point light source defined in a three-dimensional virtual space affects a shading point of a drawing screen. An influence light source identification program for causing a computer to identify such a bounding volume, which is set based on a condition given to the shading point in the computer and sets an influence range area for the shading point. An area shape determination function for determining a shape common to all the light sources, an area size determination function for stochastically selecting and determining a size of a bounding volume set for each of the light sources from a plurality of candidates, and Whether or not the light source position is included in the bounding volume set in To determine the, the light source, characterized in that to achieve the cross determination function of specifying as a light source affecting the shading point when the light source is included in the bounding volume.

  According to a non-limiting viewpoint, the influence light source identification method according to an embodiment of the present invention is based on whether or not light from a light source including a virtual point light source defined in a three-dimensional virtual space affects a shading point on a drawing screen. This method is used to identify the influence light source, and is common to all the light sources for the bounding volume that is set based on the condition given to the shading point and that sets the influence area for the shading point. Region shape determination processing for determining a shape to be performed, region size determination processing for selecting and determining a bounding volume size set for each light source from a plurality of candidates, and bounding set for each light source It is determined whether the position of the light source is included in the volume, and the light is input to the bounding volume. Characterized in that it comprises a cross-determination process for identifying a light source affecting the light source to the shading point if it contains.

  According to a non-limiting viewpoint, the influence light source identification device according to an embodiment of the present invention determines whether light from a light source including a virtual point light source defined in a three-dimensional virtual space affects a shading point of a drawing screen. This is an influence light source identification device for identifying the above, and is common to all light sources for the bounding volume that is set based on the condition given to the shading point and that defines the range of influence for the shading point. A region shape determining unit that determines a shape to be formed, a region size determining unit that randomly selects and determines a bounding volume size to be set for each light source from a plurality of candidates, and a bounding set for each light source It is determined whether the position of the light source is included in the volume, and the light source is included in the bounding volume. The light source, characterized in that it comprises a intersection determination section for specifying a light source affecting the shading point when Murrell.

  According to a non-limiting viewpoint, a drawing processing program according to an embodiment of the present invention performs a shading point drawing process in consideration of the influence of light from a light source including a virtual point light source defined in a three-dimensional virtual space. The drawing processing program to be realized in step S1 is based on the condition given to the shading point, and a shape common to all the light sources is determined for the bounding volume that is set with the shading point as a starting point and defines the area of influence for the shading point. An area shape determining function, an area size determining function for selecting and determining a bounding volume size set for each light source from a plurality of candidates, and a bounding volume set for each light source. Determine whether the position is included, bounding volume A first influence light source identification process that is an influence light source identification process by an influence light source identification program that causes the computer to implement an intersection determination function that identifies the light source as a light source that affects a shading point when the light source is included in For each light source including a virtual point light source, a light source starting area shape determination function for determining the shape of the light source starting bounding volume set from the light source as a starting point, and the size of the light source starting bounding volume for each light source from a plurality of candidates A light source starting area size determination function that is selected and determined probabilistically, and determines whether a shading point position is included in the light source starting bounding volume set for each light source starting from the light source. If the bounding volume includes the shading point, the light source is The computer is provided with a function to execute the second affected light source identification process, which is an affected light source identification process by the influence light source identification program that causes the computer to realize the intersection determination function that identifies the lighting point affecting the lighting point. A first drawing data acquisition function for acquiring first drawing data for a shading point by calculating a light source that influences the shading point by the first influence light source specifying process and an influence on the shading point of the specified light source; A second drawing data acquisition function for acquiring the second drawing data for the shading point by calculating the influence of the light source that has an influence on the shading point and the shading point of the specified light source by the influence light source specifying process of 2; Perform weighted averaging of the first drawing data and the second drawing data By calculating, an output drawing data acquisition function for acquiring output drawing data for a shading point is realized.

  Each embodiment of the present application solves one or more deficiencies.

It is a block diagram which shows the example of a structure of the influence light source identification device corresponding to at least 1 of embodiment of this invention. It is an explanatory view showing an example of setup of a bounding volume on the basis of a shading point for influence light source identification processing corresponding to at least one of the embodiments of the present invention. It is a flowchart which shows the example of the influence light source identification process corresponding to at least 1 of embodiment of this invention. It is a block diagram which shows the example of a structure of the influence light source identification device corresponding to at least 1 of embodiment of this invention. It is explanatory drawing showing the example of the setting of the bounding volume hierarchy (BVH) for the influence light source identification process corresponding to at least one of embodiment of this invention. It is explanatory drawing showing the example of the intersection determination process using BVH for the influence light source specification corresponding to at least 1 of embodiment of this invention. It is a flowchart which shows the example of the intersection determination process corresponding to at least 1 of embodiment of this invention. It is explanatory drawing explaining the combination of the light source included in the same axis parallel bounding box (AABB) in BVH. It is explanatory drawing showing the conventional concept in the case of calculating the influence of the virtual point light source (VPL) with respect to a shading point.

  Hereinafter, examples of embodiments of the present invention will be described with reference to the drawings. In addition, the various components in the example of each embodiment described below can be combined suitably in the range which a contradiction etc. do not produce. Moreover, about the content demonstrated as an example of a certain embodiment, the description may be abbreviate | omitted in other embodiment. In addition, the contents of operations and processes that are not related to the characterizing portion of each embodiment may be omitted. Furthermore, the order of the various processes constituting the various flows described below is random as long as no contradiction or the like occurs in the process contents.

[First Embodiment]
FIG. 1 is a block diagram showing an example of the configuration of an affected light source identification device 10A according to an embodiment of the present invention. The influence light source identification device 10A shown in FIG. 1 may be a device designed as a dedicated machine, but is assumed to be realizable by a general computer. In this case, the influential light source identification device 10A is a central processing unit (CPU), a graphics processing unit (GPU), a memory, and a hard disk drive that a general computer would normally have. Storage (not shown). In addition, it goes without saying that various processes are executed by a program in order to cause these general computers to function as the influence light source identification device 10A of this example.

  In the influence light source identification device 10A according to the present invention, whether light from a light source including a virtual point light source (VPL) existing in a three-dimensional virtual space affects each shading point (drawing point) of a drawing screen To determine the Then, in order to determine whether the light from the light source affects the shading point, setting of a bounding volume based on the shading point is characterized. The details will be described below.

  As shown in FIG. 1, the influential light source identification device 10A includes an area shape determination unit 11, an area size determination unit 12, and an intersection determination unit 13.

  The region shape determination unit 11 has a function of determining a shape common to all the light sources for a bounding volume that is set with the shading point as a starting point and defines an influence range region for the shading point based on a condition given to the shading point. . The condition given to the shading point refers to various conditions that affect the reflection of light including the material set at the shading point and information on the surface roughness. The bounding volume is an area that is set starting from a shading point and adopts a common shape for all light sources for each shading point, but the size is set corresponding to each light source. It refers to the area that defines the influence range of each light source. This bounding volume and an axis parallel bounding box described later are different concepts and are defined as different terms. The shape of the bounding volume is preferably a bounding sphere or a shape close to a sphere when the shading point is a diffusing surface, and a shape of an ellipsoid when the shading point is a reflecting surface. A specific shape determination method is, for example, based on the ellipsoid shape determination method using BRDF (Bidirectional Reflectance Distribution Function) disclosed in Non-Patent Document 1. The shape may be determined. Note that the corresponding shape may be determined by referring to a previously stored table using numerical conditions given to the shading points. In addition, the process of determining the shape of the bounding volume in the region shape determination unit 11 is performed for each shading point or for each material applied to the shading point based on conditions such as the material of the shading point and surface roughness information. The shape of the optimal bounding volume may be determined and stored in advance, and the shape of the bounding volume may be determined with reference to the stored information. The shape of the bounding volume determined by the region shape determination unit 11 is a shape that is commonly used in all the light sources for the target shading point.

  The region size determination unit 12 has a function of selecting and determining the size of the bounding volume set for each light source from a plurality of candidates. The region shape determination unit 11 determines the shape of the bounding volume to be used in common for all light sources, but the size of the bounding volume needs to be set for each light source. The size of the bounding volume for each light source is not uniquely determined from the conditions of the light source, but any size is selected from a plurality of candidates prepared as candidates in advance according to the probability. Here, in addition to a configuration in which two or more real size candidates are prepared and selected with a probability, the plurality of candidates is a parameter with a probability in a configuration in which the size of the bounding volume is determined using a real number of 0 or more as a parameter. It shall include those that determine the real number. The plurality of candidates need not be a finite number, and may be infinite. The plurality of size candidates may be prepared uniformly regardless of the light source, or based on the conditions regarding the light intensity of the light source such as radiant energy (radiance), The size may be changed. Any method can be used as long as the selection method is based on the probability, but for example, the probability that the optimum bounding volume size determined from the condition regarding the light intensity of the light source is selected is the highest. For other sizes, it is preferable to set the probability so that the probability of being selected decreases as the size changes from the size of the optimal bounding volume. The process of determining the size of the bounding volume with such a predetermined probability is performed for each light source. That is, the size of the bounding volume is determined for all the light sources existing in the three-dimensional virtual space.

  The intersection determination unit 13 determines whether or not the position of the light source is included in the bounding volume set for each light source, and when the light source is included in the bounding volume, the light source is used as a light source that affects the shading point. It has a function to identify. In order to specify whether the light source affects the shading point, it is determined whether the position of the light source is included in the bounding volume set for each light source. When the light source position is not included in the bounding volume, it is specified that the light source does not affect the shading point. When the light source position is included in the bounding volume, it is specified that the light source affects the shading point. The light source determined to affect the shading point is a target of calculation in the shading point drawing process.

  FIG. 2 is an explanatory diagram showing an example of setting a bounding volume based on a shading point for the influence light source identification process corresponding to at least one of the embodiments of the present invention. In FIG. 2, VPL1, VPL2, and VPL3 are provided to express the state in which light from a light source that exists outside the drawing screen of the three-dimensional virtual space is reflected by the wall surface, and these VPL1, VPL2, and VPL3 are shaded. In order to specify whether or not the point is affected, a bounding volume based on the shading point is set. In FIG. 2, as an example in the case where the shading point is a glossy surface, an ellipsoidal bounding volume is set. Then, three bounding volumes based on the shading point are set at sizes corresponding to each of VPL1, VPL2, and VPL3. In FIG. 2, the bounding volume set for VPL1 is the ellipsoid with the smallest size, and the position of VPL1 is not included in this smallest ellipsoid. Therefore, as a result of the intersection determination, VPL1 does not affect the shading point. Identified as Next, since the bounding volume set for VPL2 is the largest ellipsoid, and the position of VPL2 is included in the largest ellipsoid, as a result of the cross determination, VPL2 is a light source that affects the shading point Identified as Finally, since the bounding volume set for VPL3 is a medium-size ellipsoid, and the position of VPL3 is not included in this medium-size ellipsoid, VPL3 is a light source that does not affect the shading point. Identified as being.

  As shown in FIG. 2, (2) the light source → glossy surface → diffusion surface → viewpoint route and (4) the light source → glossy surface → glossy surface → viewpoint route are highly dispersed. , (1) Light source → Diffusion surface → Diffusion surface → Viewpoint and (3) Light source → Diffusion surface → Glossy surface → Viewpoint are low dispersion. That is, the conventional method disclosed in Non-Patent Document 1 results in high dispersion (3) It is possible to achieve low dispersion for the route of light source → diffusion surface → glossy surface → viewpoint, so the method of this example It can be said that there is a drawing scene that can avoid becoming an unpleasant video by adopting.

  Next, the influence light source identification process performed in the influence light source identification device 10A of this example will be described. FIG. 3 is a flowchart showing an example of the influence light source identification process corresponding to at least one of the embodiments of the present invention. As shown in FIG. 3, the influence light source identification process is started by first determining the shape of the bounding volume for the target shading point (step S101). Subsequently, the size of the bounding volume for each light source is selected from a plurality of candidates according to the probability (step S102). Then, for all the light sources, it is judged whether or not the position of the light source is included in the bounding volume for each light source, and if it is included, it is identified as the light source affecting the shading point (step S103). , End the process.

  As described above, according to the influential light source identification device 10A of the present example, the shape of the bounding volume starting from the shading point for the target shading point is determined, and the size of the bounding volume for each light source is set to a plurality of candidate sizes. Select according to the probability, and perform a crossing determination as to whether or not the position of the light source is included in the bounding volume for each light source. If included, specify the light source as an influence on the shading point. Thus, even when setting the bounding volume starting from the shading point, it is possible to specify an influence light source for drawing that can avoid a state where the screen becomes too dark while reducing the amount of calculation.

Second Embodiment
FIG. 4 is a block diagram showing an example of the configuration of the affected light source identification device 10B according to an embodiment of the present invention. The same components as those of the influential light source identification device 10A in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. The influence light source identification device 10B shown in FIG. 6 may be a device designed as a dedicated machine, but is the same as in the first embodiment in that it can be realized by a general computer. .

  The BVH setting unit 14 sets, for each of a plurality of light sources arranged in the three-dimensional virtual space, an axis-parallel bounding box including the light sources for each predetermined number of light sources in the lowermost layer, By repeating the process of setting an axis parallel bounding box including a predetermined number of axis parallel bounding boxes of the hierarchy while sequentially raising the hierarchy, a tree-structured bounding volume hierarchy (with the axis parallel bounding box for the light source in the three-dimensional virtual space ( The following has a function of setting BVH). In the tree structure, each axis parallel bounding box constituting the tree structure is expressed as a node, and in the case of a hierarchy, it means the height (or depth) of the node. Here, the axis parallel bounding box is also called AABB (Axis-Aligned Bounding Box), and is a plane parallel to the XY plane, a plane parallel to the XZ plane, and Y in the three-dimensional virtual space. It refers to a rectangular parallelepiped formed only by a plane parallel to the -Z plane. The BVH setting unit 14 first sets, for a plurality of light sources arranged in the three-dimensional virtual space, an axis parallel boundary box so that a predetermined number of light sources are included in one axis parallel boundary box. The predetermined number may be any number, but if the predetermined number is set to a large number, there is a possibility that the effect of reducing the amount of calculation for intersection determination may not be obtained. It is preferable that it is the number of the As an example, one axis parallel bounding box is set for two light sources. For a combination of a predetermined number of light sources, the condition that the predetermined number of light sources existing within a predetermined distance from each other are included in one axis parallel bounding box, and the difference in size of the bounding volume set corresponding to each is within the predetermined range. The predetermined number of light sources is included in one axis parallel bounding box, or is determined according to a condition that satisfies these two conditions simultaneously.

  The axis-parallel bounding box including the predetermined number of light sources becomes the lowermost axis-parallel bounding box. After setting the lowermost axis parallel bounding box, an axis parallel bounding box including a predetermined number of lowermost axis parallel bounding boxes is set. Assuming that the lowermost layer is level 1, in the layer of level 2, an axis-parallel boundary box including a predetermined number, for example, two, of axis-parallel boundary boxes of level 1 is set. This process is repeated while sequentially raising the layer. That is, in the layer of level 3, an axis parallel boundary box including a predetermined number of axis parallel boundary boxes set in the layer of level 2 is set, and in the layer of level 4, an axis parallel boundary box set in the layer of level 3 By sequentially performing processing such as setting an axis parallel bounding box that includes a predetermined number, a bounding volume hierarchy (hereinafter referred to as BVH) of the layer structure by the axis parallel bounding box is set. If this is repeated to the end, one axis parallel bounding box including all the light sources in the three-dimensional virtual space is set. However, it is set as appropriate to which layer the processing of the BVH setting is finished. It is possible. The BVH set in this way is used to reduce the amount of calculation of the influence light source identification process in the intersection determination unit 13B.

In addition, about the setting of BVH in the BVH setting part 14, the technique of the construction of BVH using the Morton code described in the following literatures can be used, for example.
[Non-patent document 2] Fast BVH construction on GPUs .: LAUTERBACH C., GARLAND M., SENGUPTA S., LUEBKE D., MANOCHA D .: Computer Graphics Forum 28, 2 (2009), 375-384.

  In addition to the function of the intersection determination unit 13 in the first embodiment, the intersection determination unit 13B applies to each of all light sources included in all the axis parallel boundary boxes below the target node at any node of the BVH. The bounding volume with the largest size among the bounding volumes set in correspondence with the bounding volume of the axis and all the axis parallel bounding boxes included in the target node are determined to be included, and included in the axis parallel bounding box that is determined not to intersect. The light source has a function of executing processing (hereinafter also referred to as BVH intersection determination processing) that identifies the light source as having no influence on the shading point. Regardless of which node of BVH is selected, there is an axis parallel bounding box at that node, and if the axis parallel bounding box is traced to the lower node, the light source is always included in the lowest node. The largest bounding volume among the bounding volumes set in correspondence with all the light sources included in all the axis parallel bounding boxes below the target node, and all the axis parallel bounding boxes included in the target node The light source that does not affect the shading point is identified by performing the intersection determination of That is, among the bounding volumes set corresponding to each of all the light sources included in all the axis-parallel bounding boxes below the target node, the size is the largest for the axis-parallel bounding box that does not intersect with the largest bounding volume. Therefore, it can be determined that the light source included in the volume does not intersect with the bounding volume set corresponding to each light source. Therefore, it is possible to omit individual intersection determination for the light sources included in the axis parallel bounding box. By performing such BVH intersection determination processing for each node included in the node when the hierarchy is deepened sequentially from the highest layer node of BVH, the intersection determination between the light source and the bounding volume of the light source is finally performed. It is possible to reduce the number of times it is performed. Note that it is not always necessary to execute the BVH intersection determination process at all nodes. For example, a node near a lower hierarchy is set to directly correspond to the light source and the light source without executing the BVH intersection determination process. The intersection determination process with the bounding volume may be performed.

  This intersection determination unit 13B is included in the bounding volume and the target node having the largest size among the bounding volumes set in correspondence with all the light sources included in all the axis parallel bounding boxes below the target node of the BVH. By performing both the intersection determination process with all the axis parallel bounding boxes and the intersection determination process between the light source and the bounding volume set corresponding to the light source, the calculation processing load is reduced. Identify light sources that affect shading points.

  FIG. 5 is an explanatory diagram showing an example of setting a bounding volume hierarchy (BVH) for the influence light source identification process corresponding to at least one of the embodiments of the present invention. FIG. 5 shows an example in which BVH is set in a three-dimensional virtual space in which eight light sources exist. In the lowest level 1 hierarchy, [1-1], [1-2], [1-3], [1-4] are set as axis parallel bounding boxes including two adjacent light sources. There is. In the hierarchy of level 2 which is the hierarchy one level above, set [2-1] as an axis parallel boundary box including the axis parallel boundary boxes of [1-1] and [1-2], and [2-2] is set as an axis parallel bounding box including the axis parallel bounding boxes of [3] and [1-4]. In the level 3 hierarchy of the top layer, [3-1] is set as an axis parallel boundary box including the axis parallel boundary boxes of [2-1] and [2-2]. In the example of FIG. 5, [3-1] is the highest node, [2-1] and [2-2] are nodes included in [3-1], and [1-1] and [2-1] [1-2] are nodes included in [2-1], and [1-3] and [1-4] are nodes included in [2-2]. Further, for simplification and explanation, in the example of FIG. 5, three types of size A, size B and size C are used as the size of the bounding volume set for each light source, and size A> size B> Size C There is a relationship of size. For convenience of explanation, although the explanation will be made by applying a rectangular axis parallel boundary box in a two-dimensional plane, in practice, a rectangular parallel axis parallel boundary box is applied to a three-dimensional space.

  FIG. 6 is an explanatory diagram showing an example of the intersection determination process using BVH for identifying an affected light source corresponding to at least one of the embodiments of the present invention. In FIG. 6, the BVH intersection determination process using the BVH constructed with a tree structure as shown in FIG. 5 will be described. First, FIG. 6A illustrates the intersection determination for the node [3-1] included in the top level 3 hierarchy. In FIG. 6A, [2-1] included in the node [3-1] and most of the bounding volumes set corresponding to all the light sources included in [2-1]. The intersection determination with the large size A bounding volume is performed. Then, as shown in FIG. 6A, the bounding volume of size A and the [2-1] axis parallel bounding box intersect. Similarly, for [2-2], the intersection determination with the largest bounding volume among the bounding volumes set in correspondence with all the light sources included in [2-2] is performed. In [2-2], when the corresponding bounding volume and the axis-parallel bounding box do not intersect, the light sources that do not affect the shading point for all the light sources existing inside the axis-parallel bounding box of [2-2] Can be identified.

  FIG. 6B shows the intersection determination at the node [2-1], which is one level deeper from the node [3-1]. In FIG. 6B, the largest size B among the bounding volumes set corresponding to the axis parallel bounding box [1-1] and all the light sources included in [1-1]. The intersection determination with the bounding volume of Then, as shown in FIG. 6B, the bounding volume of size B and the axis parallel bounding box [1-1] intersect each other. Similarly, for [1-2], the intersection determination with the largest-sized bounding volume among the bounding volumes set corresponding to each of all the light sources included in [1-2] is performed. In [1-2], when the corresponding bounding volume and the [1-2] axis parallel bounding box do not intersect, for all the light sources existing inside the [1-2] axis parallel bounding box, , And a light source that does not affect the shading point.

  FIG. 6C shows the intersection determination at the node [1-1], which is one level deeper from the node [2-1]. In FIG. 6C, the intersection determination between the light source and the bounding volume of size C set corresponding to the light source is performed. Then, as shown in FIG. 6C, the bounding volume of size C and the light source intersect. Similarly, the intersection determination with the bounding volume of the size set corresponding to the other light source is performed. In another light source, if it does not intersect the bounding volume, finally only one light source is identified as a light source affecting the shading point.

  When performing individual intersection determination for eight light sources, eight times of intersection determination processing are required. However, when the BVH intersection determination processing is employed, the BVH intersection determination is four times in the example of FIG. It can be seen that the intersection judgment between the light source and the bounding volume becomes the intersection judgment of two times in total, six times, and the number of intersection judgments can be reduced. Therefore, it can be said that the processing load reduction effect by introducing the BVH intersection determination process increases as the number of BVH nodes increases.

  Next, the flow of the influence light source identification process performed in the influence light source identification device 10B of this example will be described. FIG. 7 is a flowchart showing an example of influence light source identification processing corresponding to at least one of the embodiments of the present invention. As shown in FIG. 7, the influential light source identification process is first started by determining the shape of the bounding volume for the target shading point (step S201). Subsequently, the size of the bounding volume for each light source is selected from a plurality of candidates according to the probability (step S202). And BVH is set about the light source which exists in three-dimensional virtual space (step S203). Finally, the BVH intersection determination process is executed using the set BVH, and finally the individual intersection determination between the light source and the bounding volume is performed as a process for specifying the light source that finally affects the shading point, thereby obtaining the shading point. Are identified (step S204), and the process ends.

  FIG. 8 is an explanatory diagram illustrating combinations of light sources included in the same axis-parallel bounding box (AABB) in BVH. FIG. 8A shows a case where two light sources that are close to each other but have different sizes of bounding volumes that are set in correspondence with each other are included in the same axis-parallel bounding box (AABB). When the BVH intersection determination process is performed in the state of FIG. 8A, it is determined that the larger bounding volume and the axis parallel bounding box (AABB) intersect with each other, so that the transition to the individual intersection determination for each light source is performed. However, in the individual intersection determination, since it is determined that no intersection occurs in the intersection determination between the bounding volume of the smaller size and the light source, one intersection determination process is wasted. On the other hand, FIG. 8B shows a case where two light sources having close light source positions and close bounding volume sizes corresponding to the light source positions are included in the same axis parallel bounding box (AABB). There is. As shown in FIG. 8B, the size of the two bounding volumes is not large enough to reach the axis parallel bounding box (AABB) including the light source. Therefore, when the BVH intersection determination process is performed, the bounding of the larger size is performed. It is determined that the volume and the axis parallel bounding box (AABB) do not intersect. If determined in this way, it is possible to specify that the two light sources are light sources that do not affect the shading point without performing individual intersection determinations. If the bounding volumes set for the two light sources in FIG. 8B are of a size that intersects each light source, the two light sources are determined in two separate intersection determinations after the BVH intersection determination process. Is identified as a light source that affects the shading point, two separate intersection determinations are not wasted. That is, it is possible to perform a crossing determination without waste by including light sources having a size close to the bounding volume set in correspondence with each other in the same axis parallel bounding box (AABB). It is possible to reduce the overall processing load.

  As described above, according to the influence light source identification device 10B of the present example, the shape of the bounding volume starting from the shading point for the target shading point is determined, and the size of the bounding volume for each light source is set to a plurality of candidate sizes. Select from the probability, and for multiple light sources, set an axis parallel bounding box that includes those light sources for each predetermined number of light sources in the lowest layer, and specify the axis parallel bounding box of the layer below it every time the layer is raised By repeating the process of setting a number of axis parallel bounding boxes while sequentially raising the hierarchy, BVH of the tree structure by the axis parallel bounding box regarding the light source in the three-dimensional virtual space is set, and all the nodes below the target node of BVH Bounding volume set for each light source included in the axis parallel bounding box Intersection of the largest bounding volume among all the axis parallel bounding boxes included in the target node is determined, and the light source included in the axis parallel bounding box determined not to intersect has an effect on the shading point. Since at least one of the nodes of BVH executes the process of specifying that the light source is not a light source, as compared with the case where the intersection determination with the bounding volume set for each light source is performed individually for all light sources. It is possible to specify a light source that affects the shading point while reducing the processing load.

Third Embodiment
The affected light source identification process in the first and second embodiments determines the shape of the bounding volume starting from the shading point of interest and determines the size of the bounding volume among a plurality of candidates for each light source. Whether or not the light source is a light source that affects the shading point is specified based on whether or not the position of the light source is included in the bounding volume in the case of selecting from the probability. The influence light source identification process in the second embodiment and the influence light source identification process disclosed in Non-Patent Document 1 may be used in combination to realize the shading point drawing process.

The influence light source identification process in the first and second embodiments is a first influence light source identification process, and the influence light source identification process disclosed in Non-Patent Document 1 is a second influence light source identification process. Here, the second influence light source identification process includes a light source starting area shape determining unit that determines a shape of a light source starting bounding volume for each light source including a virtual point light source, and a plurality of light source starting bounding volume sizes for each light source. A light source origin area size determination unit which selects probabilistically from among the candidates and determines, and whether or not the position of a shading point is included in the light source origin bounding volume set starting from the light source for each light source is determined When the light source starting point bounding volume includes the shading point, the second affected light source specifying process is realized by the affected light source specifying device including the intersection determination unit that specifies the light source as the light source affecting the shading point. Shall be

  The drawing processing apparatus that realizes the shading point drawing processing calculates the first drawing data on the shading point by calculating the influence of the light source that has an influence on the shading point and the shading point of the specified light source by the first influence light source specifying processing. The first drawing data acquisition unit for acquiring the shading point and the second drawing data on the shading point are obtained by calculating the influence on the shading point of the light source and the light source specified by the second influence light source specifying process. A second drawing data acquisition unit, and an output drawing data acquisition unit that acquires output drawing data for a shading point by calculating a weighted average of the acquired first drawing data and the second drawing data.

Here, the weighted average in the third embodiment is assumed to be a weighted average by Multiple Importance Sampling. The method described in the following document can be adopted as the weighted average according to this Multiple Importance Sampling.
[Non-Patent Document 3] Optimally Combining Sampling Techniques for Monte Carlo Rendering.: E. Veach and LJ Guibas.: In SIGGRAPH '95. 419-428.

  Here, as shown in FIG. 2, the first influence light source identification process is (2) a path of light source → glossy surface → diffusion surface → viewpoint, and (4) light source → glossy surface → glossy surface → viewpoint. In the case of the route, the dispersion is high, and as shown in FIG. 9, the second affected light source identification process is (3) light source → diffuse surface → glossy surface → viewpoint (4) light source → Glossy surface → Glossy surface → View path was highly dispersed. However, when the output drawing data for the shading point is obtained by calculating the weighted average of the first drawing data and the second drawing data as in the drawing processing apparatus of this example, all of (1) to (4) are obtained. The result is low variance for the pattern. Also for the pattern of (4) that is highly dispersed in both the first affected light source identification process and the second affected light source identification process, the effects of dispersion are averaged to obtain low dispersion by performing weighted averaging. Is possible.

  As described above, according to the drawing processing apparatus of the present example, the first drawing data on the shading points obtained by the calculation based on the light sources that influence the shading points and the specified light sources by the first influential light source specifying process, The drawing data to be output is obtained by performing a weighted average between the light source that affects the shading point by the second influence light source specifying process and the second drawing data for the shading point obtained by the calculation based on the specified light source. As a result, the weighted average can be made to have a low variance with respect to a drawing scene that is highly dispersed in each of the first influential light source identification process and the second influential light source identification process, resulting in continuous images It is possible to obtain a comfortable image by preventing the brightness of the same drawing point from becoming brighter or darker .

  As explained above, each embodiment of the present application solves one or more deficiencies. In addition, the effect by each embodiment is an example of a non-limiting effect or an effect.

10A, 10B Influence light source identification device 11 Region shape determination unit 12 Region size determination unit 13, 13B Crossing determination unit 14 BVH setting unit

Claims (7)

An influence light source identification program for causing a computer to identify whether light from a light source including a virtual point light source defined in a three-dimensional virtual space affects a shading point of a drawing screen,
On the computer
An area shape determination function that determines a shape common to all light sources for a bounding volume that is set with the shading point as a starting point and defines an affected area for the shading point based on a condition given to the shading point;
An area size determination function of selecting the size of the bounding volume to be set for each light source from among a plurality of candidates probabilistically;
An intersection determination function that determines whether or not the position of the light source is included in the bounding volume set for each light source, and identifies the light source as a light source that affects a shading point when the light source is included in the bounding volume Impact light source identification program to realize and. On the computer
For a plurality of the light sources arranged in the three-dimensional virtual space, an axis parallel boundary box including those light sources is set for each predetermined number of light sources in the lowermost layer, and the axis parallel boundary of the layer below it is set each time the layer is raised By repeating the process of setting an axis parallel boundary box including a predetermined number of boxes while raising the hierarchy sequentially, a bounding volume hierarchy (hereinafter referred to as BVH) of a tree structure by an axis parallel boundary box related to a light source in a three-dimensional virtual space. Implement the BVH setting function to be set,
The intersection determination function is, at any one of the nodes of the BVH, the largest size bounding among bounding volumes set corresponding to each of all the light sources included in all the axis parallel bounding boxes of the target node. Performs intersection determination between the volume and all the axis parallel bounding boxes included in the target node, and identifies light sources included in the axis parallel bounding box determined not to intersect as light sources that do not affect the shading point. The influence light source identification program according to claim 1, comprising a function of executing a process. 3. The influence light source according to claim 2, wherein the BVH setting function sets the axis parallel boundary box so that a predetermined number of light sources existing within a predetermined distance from each other are included in one axis parallel boundary box in the lowest layer. Specific program. The BVH setting function includes an axis parallel bounding box so that a predetermined number of light sources whose difference in size of the bounding volume set corresponding to each is included in a predetermined range in the lowest layer is included in one axis parallel bounding box. The influence light source identification program according to claim 2 or 3. An influence light source identification method for identifying whether light from a light source including a virtual point light source defined in a three-dimensional virtual space affects a shading point of a drawing screen,
Based on the conditions given to the shading point, an area shape determination process for determining a shape common to all the light sources for the bounding volume that is set with the shading point as a starting point and defines an affected area for the shading point;
An area size determination process in which the size of the bounding volume to be set for each light source is probabilistically selected and determined from among a plurality of candidates;
Cross determination processing for determining whether or not the position of the light source is included in the bounding volume set for each light source, and specifying the light source as a light source that affects the shading point when the light source is included in the bounding volume Impact light source identification method including and. An influence light source specifying device for specifying whether light from a light source including a virtual point light source defined in a three-dimensional virtual space affects a shading point of a drawing screen,
An area shape determination unit which determines a shape common to all light sources for a bounding volume, which is set using the shading point as a starting point and determines an influence range area for the shading point based on a condition given to the shading point;
An area size determination unit which stochastically selects and determines a size of a bounding volume set for each light source from a plurality of candidates;
An intersection determination unit that determines whether or not the position of the light source is included in the bounding volume set for each light source, and identifies the light source as the light source that affects the shading point when the light source is included in the bounding volume An influence light source identification device comprising: A drawing processing program for causing a computer to perform a drawing process of a shading point in consideration of the influence of light from a light source including a virtual point light source defined in a three-dimensional virtual space,
A first affected light source identification process, which is an influenced light source identification process according to the influenced light source identification program according to any one of claims 1 to 4.
A light source origin area shape determining function for determining the shape of a light source origin bounding volume set starting from the light source for each light source including a virtual point light source, and the size of the light source origin bounding volume for each light source A light source origin area size determining function which selects and determines in a probabilistic manner, and whether or not the position of a shading point is included in a light source origin bounding volume set starting from the light source for each light source is determined. Second influence light source specification that is an influence light source specification process by the influence light source specification program that causes the computer to realize an intersection determination function that specifies the light source as a light source affecting the shading point when the bounding volume includes the shading point It has a function to execute processing and
On the computer
A first drawing data acquisition function for acquiring first drawing data for a shading point by calculating an influence on the shading point of the light source that is affected by the first influence light source specifying process and the light source specified;
A second drawing data acquisition function of acquiring second drawing data for a shading point by calculating an influence on the shading point of the light source and the specified light source affecting the shading point by the second influence light source identification process;
A drawing processing program that realizes an output drawing data acquisition function of acquiring output drawing data for a shading point by calculating a weighted average of the acquired first drawing data and the second drawing data.

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