pub struct Slice<R: Resources> {
pub start: VertexCount,
pub end: VertexCount,
pub base_vertex: VertexCount,
pub instances: Option<InstanceParams>,
pub buffer: IndexBuffer<R>,
}Expand description
A Slice dictates in which and in what order vertices get processed. It is required for
processing a PSO.
§Overview
A Slice in gfx has a different meaning from the term slice as employed more broadly in rust (&[T]).
A Slice object in essence dictates in what order the vertices in a VertexBuffer get
processed. To do this, it contains an internal index-buffer. This Buffer is a list of
indices into this VertexBuffer (vertex-index). A vertex-index of 0 represents the first
vertex in the VertexBuffer, a vertex-index of 1 represents the second, 2 represents the
third, and so on. The vertex-indices in the index-buffer are read in order; every vertex-index
tells the pipeline which vertex to process next.
Because the same index can re-appear multiple times, duplicate-vertices can be avoided. For instance, if you want to draw a square, you need two triangles, and thus six vertices. Because the same index can reappear multiple times, this means we can instead use 4 vertices, and 6 vertex-indices.
This index-buffer has a few variants. See the IndexBuffer documentation for a detailed
description.
The start and end fields say where in the index-buffer to start and stop reading.
Setting start to 0, and end to the length of the index-buffer, will cause the entire
index-buffer to be processed. The base_vertex dictates the index of the first vertex
in the VertexBuffer. This essentially moves the the start of the VertexBuffer, to the
vertex with this index.
§Constuction & Handling
The Slice structure can be constructed automatically when using a Factory to create a
vertex buffer. If needed, it can also be created manually.
A Slice is required to process a PSO, as it contains the needed information on in what order
to draw which vertices. As such, every draw call on an Encoder requires a Slice.
Fields§
§start: VertexCountThe start index of the index-buffer. Processing will start at this location in the index-buffer.
end: VertexCountThe end index in the index-buffer. Processing will stop at this location (exclusive) in the index buffer.
base_vertex: VertexCountThis is the index of the first vertex in the VertexBuffer. This value will be added to
every index in the index-buffer, effectively moving the start of the VertexBuffer to this
base-vertex.
instances: Option<InstanceParams>Instancing configuration.
buffer: IndexBuffer<R>Represents the type of index-buffer used.
Implementations§
Source§impl<R: Resources> Slice<R>
impl<R: Resources> Slice<R>
Sourcepub fn from_vertex_count(count: VertexCount) -> Self
pub fn from_vertex_count(count: VertexCount) -> Self
Creates a new Slice with a given vertex count.
Sourcepub fn new_match_vertex_buffer<V>(vbuf: &Buffer<R, V>) -> Self
pub fn new_match_vertex_buffer<V>(vbuf: &Buffer<R, V>) -> Self
Creates a new Slice to match the supplied vertex buffer, from start to end, in order.
Sourcepub fn get_prim_count(&self, prim: Primitive) -> u32
pub fn get_prim_count(&self, prim: Primitive) -> u32
Calculates the number of primitives of the specified type in this Slice.
Sourcepub fn split_at(&self, mid: VertexCount) -> (Self, Self)
pub fn split_at(&self, mid: VertexCount) -> (Self, Self)
Divides one slice into two at an index.
The first will contain the range in the index-buffer [self.start, mid) (excluding the index mid itself) and the second will contain the range [mid, self.end).