1//! Types needed for GPU mesh uniform building.
2
3/// Per-frame data that the CPU supplies to the GPU.
4struct MeshInput {
5    /// The model transform.
6    world_from_local: mat3x4<f32>,
7    /// The lightmap UV rect, packed into 64 bits.
8    lightmap_uv_rect: vec2<u32>,
9    /// Various flags.
10    flags: u32,
11    /// The index of the `PreviousMeshInput` uniform in the buffer, or `u32::MAX`
12    /// if there's no such uniform.
13    previous_input_index: u32,
14    first_vertex_index: u32,
15    first_index_index: u32,
16    index_count: u32,
17    current_skin_index: u32,
18    /// Low 16 bits: index of the material inside the bind group data.
19    /// High 16 bits: index of the lightmap in the binding array.
20    material_and_lightmap_bind_group_slot: u32,
21    timestamp: u32,
22    /// User supplied index to identify the mesh instance
23    tag: u32,
24    /// The index of the morph descriptor for this mesh instance in the
25    /// `morph_descriptors` table.
26    ///
27    /// If the mesh has no morph targets, this is `u32::MAX`.
28    morph_descriptor_index: u32,
29    metadata_index: u32
30}
31
32/// Per-mesh-instance data that we retain from the previous frame.
33struct PreviousMeshInput {
34    /// The model transform.
35    world_from_local: mat3x4<f32>,
36};
37
38/// The `wgpu` indirect parameters structure. This is a union of two structures.
39/// For more information, see the corresponding comment in
40/// `gpu_preprocessing.rs`.
41struct IndirectParametersIndexed {
42    /// `vertex_count` or `index_count`.
43    index_count: u32,
44    /// `instance_count` in both structures.
45    instance_count: u32,
46    /// `first_vertex` or `first_index`.
47    first_index: u32,
48    /// `base_vertex` or `first_instance`.
49    base_vertex: u32,
50    /// A read-only copy of `instance_index`.
51    first_instance: u32,
52}
53
54struct IndirectParametersNonIndexed {
55    vertex_count: u32,
56    instance_count: u32,
57    base_vertex: u32,
58    first_instance: u32,
59}
60
61/// Information needed to construct indirect draw parameters for a single draw.
62///
63/// Note that is per-*draw* (i.e. per-mesh), not per-mesh-instance or
64/// per-batch-set. A single multi-draw indirect call can perform multiple draws.
65///
66/// Typically, the uniform allocation and mesh preprocessing phases fill in this
67/// structure. However, parts of it may be filled in on the CPU for objects that
68/// aren't multidrawn.
69struct IndirectParametersMetadata {
70    /// The index of the first `MeshUniform` for this draw in the mesh uniform
71    /// buffer.
72    ///
73    /// `MeshUniform`s for all instances are stored consecutively.
74    ///
75    /// This is filled in in the `allocate_uniforms` shader, or on the CPU when
76    /// multidraw isn't in use.
77    base_output_index: u32,
78
79    /// The index of this batch set in the `IndirectBatchSet` array.
80    ///
81    /// This is filled in in the `allocate_uniforms` shader, or on the CPU when
82    /// multidraw isn't in use.
83    batch_set_index: u32,
84
85    /// The index of the mesh in the `MeshInput` buffer.
86    ///
87    /// The mesh preprocessing shader fills this in.
88    mesh_index: u32,
89
90    /// The number of instances that were visible last frame (if occlusion
91    /// culling is in use) or that were visible at all (if occlusion culling
92    /// isn't in use).
93    @if(WRITE_INDIRECT_PARAMETERS_METADATA)
94    early_instance_count: atomic<u32>,
95    /// The number of instances that were visible this frame if occlusion culling
96    /// is in use.
97    @if(WRITE_INDIRECT_PARAMETERS_METADATA)
98    late_instance_count: atomic<u32>,
99    /// The number of instances that were visible last frame (if occlusion
100    /// culling is in use) or that were visible at all (if occlusion culling
101    /// isn't in use).
102    @if(!WRITE_INDIRECT_PARAMETERS_METADATA)
103    early_instance_count: u32,
104    /// The number of instances that were visible this frame if occlusion culling
105    /// is in use.
106    @if(!WRITE_INDIRECT_PARAMETERS_METADATA)
107    late_instance_count: u32,
108}
109
110struct IndirectBatchSet {
111    indirect_parameters_count: atomic<u32>,
112    indirect_parameters_base: u32,
113}
114
115/// One invocation of this compute shader: i.e. one mesh instance in a view.
116struct PreprocessWorkItem {
117    /// The index of the `MeshInput` in the `current_input` buffer that we read
118    /// from.
119    input_index: u32,
120    /// In direct mode, the index of the `Mesh` in `output` that we write to. In
121    /// indirect mode, the index of the `IndirectParameters` in
122    /// `indirect_parameters` that we write to.
123    output_or_indirect_parameters_index: u32,
124}
125
126/// Information about each bin in a batch set.
127///
128/// This is maintained by the CPU and cached for bins that don't change from
129/// frame to frame.
130struct BinMetadata {
131    /// The index of the indirect parameters for this bin, relative to the first
132    /// indirect parameter index for the batch set.
133    ///
134    /// That is, the final indirect parameters index for this bin is
135    /// `first_indirect_parameters_index` in the `UniformAllocationMetadata` plus
136    /// this value.
137    indirect_parameters_offset: u32,
138
139    /// The index of the bin that this metadata corresponds to.
140    ///
141    /// The GPU doesn't use this, but the CPU does in order to perform the
142    /// reverse mapping from bin metadata index back to the bin. We could store
143    /// this in a non-GPU-accessible buffer, but I figured the extra complexity
144    /// wasn't worth it.
145    bin_index: u32,
146
147    /// The number of mesh instances in this bin.
148    instance_count: u32,
149};