Struct gfx::Slice
[−]
[src]
pub struct Slice<R: Resources> { pub start: VertexCount, pub end: VertexCount, pub base_vertex: VertexCount, pub instances: Option<InstanceParams>, pub buffer: IndexBuffer<R>, }
A Slice
dictates in which and in what order vertices get processed. It is required for
processing a PSO.
Overview
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: VertexCount
The start index of the index-buffer. Processing will start at this location in the index-buffer.
end: VertexCount
The end index in the index-buffer. Processing will stop at this location (exclusive) in the index buffer.
base_vertex: VertexCount
This 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.
Methods
impl<R: Resources> Slice<R>
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fn new_match_vertex_buffer<V>(vbuf: &Buffer<R, V>) -> Self where V: Structure<Format>
Creates a new Slice
to match the supplied vertex buffer, from start to end, in order.
fn get_prim_count(&self, prim: Primitive) -> u32
Calculates the number of primitives of the specified type in this Slice
.
Trait Implementations
impl<R: Clone + Resources> Clone for Slice<R>
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fn clone(&self) -> Slice<R>
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
1.0.0
Performs copy-assignment from source
. Read more