[Ray-tracing] Change index offset to first index

CHANGELOG.md

@@ -179,6 +179,7 @@ By @wumpf in [#6849](https://github.com/gfx-rs/wgpu/pull/6849).
 - Add actual sample type to `CreateBindGroupError::InvalidTextureSampleType` error message. By @ErichDonGubler in [#6530](https://github.com/gfx-rs/wgpu/pull/6530).
 - Improve binding error to give a clearer message when there is a mismatch between resource binding as it is in the shader and as it is in the binding layout. By @eliemichel in [#6553](https://github.com/gfx-rs/wgpu/pull/6553).
 - `Surface::configure` and `Surface::get_current_texture` are no longer fatal. By @alokedesai in [#6253](https://github.com/gfx-rs/wgpu/pull/6253)
+- Rename `BlasTriangleGeometry::index_buffer_offset` to `BlasTriangleGeometry::first_index`. By @Vecvec in [#6873](https://github.com/gfx-rs/wgpu/pull/6873/files)
 
 ##### D3D12
 

examples/src/ray_cube_compute/mod.rs

@@ -374,7 +374,7 @@ impl crate::framework::Example for Example {
                         first_vertex: 0,
                         vertex_stride: mem::size_of::<Vertex>() as u64,
                         index_buffer: Some(&index_buf),
-                        index_buffer_offset: Some(0),
+                        first_index: Some(0),
                         transform_buffer: None,
                         transform_buffer_offset: None,
                     },

examples/src/ray_cube_fragment/mod.rs

@@ -248,7 +248,7 @@ impl crate::framework::Example for Example {
                         first_vertex: 0,
                         vertex_stride: mem::size_of::<Vertex>() as u64,
                         index_buffer: Some(&index_buf),
-                        index_buffer_offset: Some(0),
+                        first_index: Some(0),
                         transform_buffer: None,
                         transform_buffer_offset: None,
                     },

examples/src/ray_scene/mod.rs

@@ -264,7 +264,7 @@ fn upload_scene_components(
                     first_vertex: vertex_range.start as u32,
                     vertex_stride: mem::size_of::<Vertex>() as u64,
                     index_buffer: Some(&indices),
-                    index_buffer_offset: Some(scene.geometries[i].0.start as u64 * 4),
+                    first_index: Some(scene.geometries[i].0.start as u32),
                     transform_buffer: None,
                     transform_buffer_offset: None,
                 })

examples/src/ray_shadows/mod.rs

@@ -258,7 +258,7 @@ impl crate::framework::Example for Example {
                         first_vertex: 0,
                         vertex_stride: mem::size_of::<Vertex>() as u64,
                         index_buffer: Some(&index_buf),
-                        index_buffer_offset: Some(0),
+                        first_index: Some(0),
                         transform_buffer: None,
                         transform_buffer_offset: None,
                     },

examples/src/ray_traced_triangle/mod.rs

@@ -216,9 +216,9 @@ impl crate::framework::Example for Example {
                     vertex_buffer: &vertex_buffer,
                     first_vertex: 0,
                     vertex_stride: mem::size_of::<[f32; 3]>() as wgpu::BufferAddress,
-                    // in this case since one triangle gets no compression from an index buffer `index_buffer` and `index_buffer_offset` could be `None`.
+                    // in this case since one triangle gets no compression from an index buffer `index_buffer` and `first_index` could be `None`.
                     index_buffer: Some(&index_buffer),
-                    index_buffer_offset: Some(0),
+                    first_index: Some(0),
                     transform_buffer: None,
                     transform_buffer_offset: None,
                 }]),

player/src/lib.rs

@@ -133,7 +133,7 @@ impl GlobalPlay for wgc::global::Global {
                                         transform_buffer: tg.transform_buffer,
                                         first_vertex: tg.first_vertex,
                                         vertex_stride: tg.vertex_stride,
-                                        index_buffer_offset: tg.index_buffer_offset,
+                                        first_index: tg.first_index,
                                         transform_buffer_offset: tg.transform_buffer_offset,
                                     }
                                 });
@@ -171,7 +171,7 @@ impl GlobalPlay for wgc::global::Global {
                                         transform_buffer: tg.transform_buffer,
                                         first_vertex: tg.first_vertex,
                                         vertex_stride: tg.vertex_stride,
-                                        index_buffer_offset: tg.index_buffer_offset,
+                                        first_index: tg.first_index,
                                         transform_buffer_offset: tg.transform_buffer_offset,
                                     }
                                 });

tests/tests/ray_tracing/as_build.rs

@@ -75,7 +75,7 @@ impl AsBuildContext {
                 first_vertex: 0,
                 vertex_stride: mem::size_of::<[f32; 3]>() as BufferAddress,
                 index_buffer: None,
-                index_buffer_offset: None,
+                first_index: None,
                 transform_buffer: None,
                 transform_buffer_offset: None,
             }]),
@@ -406,7 +406,7 @@ fn build_with_transform(ctx: TestingContext) {
                 first_vertex: 0,
                 vertex_stride: mem::size_of::<[f32; 3]>() as BufferAddress,
                 index_buffer: None,
-                index_buffer_offset: None,
+                first_index: None,
                 transform_buffer: Some(&transform),
                 transform_buffer_offset: Some(0),
             }]),

tests/tests/ray_tracing/as_use_after_free.rs

@@ -78,7 +78,7 @@ fn acceleration_structure_use_after_free(ctx: TestingContext) {
                 first_vertex: 0,
                 vertex_stride: mem::size_of::<[f32; 3]>() as BufferAddress,
                 index_buffer: None,
-                index_buffer_offset: None,
+                first_index: None,
                 transform_buffer: None,
                 transform_buffer_offset: None,
             }]),

tests/tests/ray_tracing/scene/mod.rs

@@ -85,7 +85,7 @@ fn acceleration_structure_build(ctx: &TestingContext, use_index_buffer: bool) {
                 first_vertex: 0,
                 vertex_stride: mem::size_of::<mesh_gen::Vertex>() as u64,
                 index_buffer: use_index_buffer.then_some(&index_buffer),
-                index_buffer_offset: use_index_buffer.then_some(0),
+                first_index: use_index_buffer.then_some(0),
                 transform_buffer: None,
                 transform_buffer_offset: None,
             }]),

wgpu-core/src/command/ray_tracing.rs

@@ -109,7 +109,7 @@ impl Global {
                                     transform_buffer: tg.transform_buffer,
                                     first_vertex: tg.first_vertex,
                                     vertex_stride: tg.vertex_stride,
-                                    index_buffer_offset: tg.index_buffer_offset,
+                                    first_index: tg.first_index,
                                     transform_buffer_offset: tg.transform_buffer_offset,
                                 })
                                 .collect(),
@@ -149,7 +149,7 @@ impl Global {
                         transform_buffer: tg.transform_buffer,
                         first_vertex: tg.first_vertex,
                         vertex_stride: tg.vertex_stride,
-                        index_buffer_offset: tg.index_buffer_offset,
+                        first_index: tg.first_index,
                         transform_buffer_offset: tg.transform_buffer_offset,
                     });
                     BlasGeometries::TriangleGeometries(Box::new(iter))
@@ -408,7 +408,7 @@ impl Global {
                                     transform_buffer: tg.transform_buffer,
                                     first_vertex: tg.first_vertex,
                                     vertex_stride: tg.vertex_stride,
-                                    index_buffer_offset: tg.index_buffer_offset,
+                                    first_index: tg.first_index,
                                     transform_buffer_offset: tg.transform_buffer_offset,
                                 })
                                 .collect(),
@@ -461,7 +461,7 @@ impl Global {
                         transform_buffer: tg.transform_buffer,
                         first_vertex: tg.first_vertex,
                         vertex_stride: tg.vertex_stride,
-                        index_buffer_offset: tg.index_buffer_offset,
+                        first_index: tg.first_index,
                         transform_buffer_offset: tg.transform_buffer_offset,
                     });
                     BlasGeometries::TriangleGeometries(Box::new(iter))
@@ -979,7 +979,7 @@ fn iter_blas<'a>(
                             Ok(buffer) => buffer,
                             Err(_) => return Err(BuildAccelerationStructureError::InvalidBufferId),
                         };
-                        if mesh.index_buffer_offset.is_none()
+                        if mesh.first_index.is_none()
                             || mesh.size.index_count.is_none()
                             || mesh.size.index_count.is_none()
                         {
@@ -1110,11 +1110,8 @@ fn iter_buffers<'a, 'b>(
                 wgt::IndexFormat::Uint16 => 2,
                 wgt::IndexFormat::Uint32 => 4,
             };
-            if mesh.index_buffer_offset.unwrap() % index_stride != 0 {
-                return Err(BuildAccelerationStructureError::UnalignedIndexBufferOffset(
-                    index_buffer.error_ident(),
-                ));
-            }
+            // since byte sizes of all the index formats are powers of two we could bitshift instead of multiplying
+            let offset = mesh.first_index.unwrap() as u64 * index_stride;
             let index_buffer_size = mesh.size.index_count.unwrap() as u64 * index_stride;
 
             if mesh.size.index_count.unwrap() % 3 != 0 {
@@ -1123,23 +1120,18 @@ fn iter_buffers<'a, 'b>(
                     mesh.size.index_count.unwrap(),
                 ));
             }
-            if index_buffer.size
-                < mesh.size.index_count.unwrap() as u64 * index_stride
-                    + mesh.index_buffer_offset.unwrap()
-            {
+            if index_buffer.size < mesh.size.index_count.unwrap() as u64 * index_stride + offset {
                 return Err(BuildAccelerationStructureError::InsufficientBufferSize(
                     index_buffer.error_ident(),
                     index_buffer.size,
-                    mesh.size.index_count.unwrap() as u64 * index_stride
-                        + mesh.index_buffer_offset.unwrap(),
+                    mesh.size.index_count.unwrap() as u64 * index_stride + offset,
                 ));
             }
 
             cmd_buf_data.buffer_memory_init_actions.extend(
                 index_buffer.initialization_status.read().create_action(
                     index_buffer,
-                    mesh.index_buffer_offset.unwrap()
-                        ..(mesh.index_buffer_offset.unwrap() + index_buffer_size),
+                    offset..(offset + index_buffer_size),
                     MemoryInitKind::NeedsInitializedMemory,
                 ),
             );
@@ -1204,13 +1196,17 @@ fn iter_buffers<'a, 'b>(
             first_vertex: mesh.first_vertex,
             vertex_count: mesh.size.vertex_count,
             vertex_stride: mesh.vertex_stride,
-            indices: index_buffer.map(|index_buffer| hal::AccelerationStructureTriangleIndices::<
-                dyn hal::DynBuffer,
-            > {
-                format: mesh.size.index_format.unwrap(),
-                buffer: Some(index_buffer.as_ref()),
-                offset: mesh.index_buffer_offset.unwrap() as u32,
-                count: mesh.size.index_count.unwrap(),
+            indices: index_buffer.map(|index_buffer| {
+                let index_stride = match mesh.size.index_format.unwrap() {
+                    wgt::IndexFormat::Uint16 => 2,
+                    wgt::IndexFormat::Uint32 => 4,
+                };
+                hal::AccelerationStructureTriangleIndices::<dyn hal::DynBuffer> {
+                    format: mesh.size.index_format.unwrap(),
+                    buffer: Some(index_buffer.as_ref()),
+                    offset: mesh.first_index.unwrap() * index_stride,
+                    count: mesh.size.index_count.unwrap(),
+                }
             }),
             transform: transform_buffer.map(|transform_buffer| {
                 hal::AccelerationStructureTriangleTransform {

wgpu-core/src/ray_tracing.rs

@@ -172,7 +172,7 @@ pub struct BlasTriangleGeometry<'a> {
     pub transform_buffer: Option<BufferId>,
     pub first_vertex: u32,
     pub vertex_stride: BufferAddress,
-    pub index_buffer_offset: Option<BufferAddress>,
+    pub first_index: Option<u32>,
     pub transform_buffer_offset: Option<BufferAddress>,
 }
 
@@ -243,7 +243,7 @@ pub struct TraceBlasTriangleGeometry {
     pub transform_buffer: Option<BufferId>,
     pub first_vertex: u32,
     pub vertex_stride: BufferAddress,
-    pub index_buffer_offset: Option<BufferAddress>,
+    pub first_index: Option<u32>,
     pub transform_buffer_offset: Option<BufferAddress>,
 }
 

wgpu/src/api/blas.rs

@@ -102,8 +102,8 @@ pub struct BlasTriangleGeometry<'a> {
     pub vertex_stride: wgt::BufferAddress,
     /// Index buffer (optional).
     pub index_buffer: Option<&'a Buffer>,
-    /// Index buffer offset in bytes (optional, required if index buffer is present).
-    pub index_buffer_offset: Option<wgt::BufferAddress>,
+    /// Index buffer offset as a factor of the size of the index type (optional, required if index buffer is present).
+    pub first_index: Option<u32>,
     /// Transform buffer containing 3x4 (rows x columns, row major) affine transform matrices `[f32; 12]` (optional).
     pub transform_buffer: Option<&'a Buffer>,
     /// Transform buffer offset in bytes (optional, required if transform buffer is present).

wgpu/src/backend/wgpu_core.rs

@@ -2445,7 +2445,7 @@ impl dispatch::CommandEncoderInterface for CoreCommandEncoder {
                             transform_buffer_offset: tg.transform_buffer_offset,
                             first_vertex: tg.first_vertex,
                             vertex_stride: tg.vertex_stride,
-                            index_buffer_offset: tg.index_buffer_offset,
+                            first_index: tg.first_index,
                         }
                     });
                     wgc::ray_tracing::BlasGeometries::TriangleGeometries(Box::new(iter))
@@ -2495,7 +2495,7 @@ impl dispatch::CommandEncoderInterface for CoreCommandEncoder {
                             transform_buffer_offset: tg.transform_buffer_offset,
                             first_vertex: tg.first_vertex,
                             vertex_stride: tg.vertex_stride,
-                            index_buffer_offset: tg.index_buffer_offset,
+                            first_index: tg.first_index,
                         }
                     });
                     wgc::ray_tracing::BlasGeometries::TriangleGeometries(Box::new(iter))