Bug reproducer

Author: Lichtso

examples/features/src/ray_cube_fragment/mod.rs

@@ -62,7 +62,14 @@ fn create_vertices() -> (Vec<Vertex>, Vec<u16>) {
         20, 21, 22, 22, 23, 20, // back
     ];
 
-    (vertex_data.to_vec(), index_data.to_vec())
+    (
+        vertex_data.to_vec(),
+        std::iter::repeat(index_data)
+            .flatten()
+            .take(153 * 3)
+            .cloned()
+            .collect(),
+    )
 }
 
 #[repr(C)]
@@ -98,6 +105,7 @@ struct Example {
     uniforms: Uniforms,
     uniform_buf: wgpu::Buffer,
     blas: wgpu::Blas,
+    blas_with_one_too_much_triangles: wgpu::Blas,
     tlas_package: wgpu::TlasPackage,
     pipeline: wgpu::RenderPipeline,
     bind_group: wgpu::BindGroup,
@@ -168,7 +176,7 @@ impl crate::framework::Example for Example {
             vertex_format: wgpu::VertexFormat::Float32x3,
             vertex_count: vertex_data.len() as u32,
             index_format: Some(wgpu::IndexFormat::Uint16),
-            index_count: Some(index_data.len() as u32),
+            index_count: Some(index_data.len() as u32 - 3),
             flags: wgpu::AccelerationStructureGeometryFlags::OPAQUE,
         };
 
@@ -183,6 +191,26 @@ impl crate::framework::Example for Example {
             },
         );
 
+        let blas_with_one_too_much_triangles_geo_size_desc =
+            wgpu::BlasTriangleGeometrySizeDescriptor {
+                vertex_format: wgpu::VertexFormat::Float32x3,
+                vertex_count: vertex_data.len() as u32,
+                index_format: Some(wgpu::IndexFormat::Uint16),
+                index_count: Some(index_data.len() as u32),
+                flags: wgpu::AccelerationStructureGeometryFlags::OPAQUE,
+            };
+
+        let blas_with_one_too_much_triangles = device.create_blas(
+            &wgpu::CreateBlasDescriptor {
+                label: None,
+                flags: wgpu::AccelerationStructureFlags::PREFER_FAST_TRACE,
+                update_mode: wgpu::AccelerationStructureUpdateMode::Build,
+            },
+            wgpu::BlasGeometrySizeDescriptors::Triangles {
+                descriptors: vec![blas_with_one_too_much_triangles_geo_size_desc.clone()],
+            },
+        );
+
         let tlas = device.create_tlas(&wgpu::CreateTlasDescriptor {
             label: None,
             flags: wgpu::AccelerationStructureFlags::PREFER_FAST_TRACE,
@@ -243,22 +271,38 @@ impl crate::framework::Example for Example {
             device.create_command_encoder(&wgpu::CommandEncoderDescriptor { label: None });
 
         encoder.build_acceleration_structures(
-            iter::once(&wgpu::BlasBuildEntry {
-                blas: &blas,
-                geometry: wgpu::BlasGeometries::TriangleGeometries(vec![
-                    wgpu::BlasTriangleGeometry {
-                        size: &blas_geo_size_desc,
-                        vertex_buffer: &vertex_buf,
-                        first_vertex: 0,
-                        vertex_stride: mem::size_of::<Vertex>() as u64,
-                        index_buffer: Some(&index_buf),
-                        first_index: Some(0),
-                        transform_buffer: None,
-                        transform_buffer_offset: None,
-                    },
-                ]),
-            }),
-            // iter::empty(),
+            vec![
+                &wgpu::BlasBuildEntry {
+                    blas: &blas,
+                    geometry: wgpu::BlasGeometries::TriangleGeometries(vec![
+                        wgpu::BlasTriangleGeometry {
+                            size: &blas_geo_size_desc,
+                            vertex_buffer: &vertex_buf,
+                            first_vertex: 0,
+                            vertex_stride: mem::size_of::<Vertex>() as u64,
+                            index_buffer: Some(&index_buf),
+                            first_index: Some(0),
+                            transform_buffer: None,
+                            transform_buffer_offset: None,
+                        },
+                    ]),
+                },
+                &wgpu::BlasBuildEntry {
+                    blas: &blas_with_one_too_much_triangles,
+                    geometry: wgpu::BlasGeometries::TriangleGeometries(vec![
+                        wgpu::BlasTriangleGeometry {
+                            size: &blas_with_one_too_much_triangles_geo_size_desc,
+                            vertex_buffer: &vertex_buf,
+                            first_vertex: 0,
+                            vertex_stride: mem::size_of::<Vertex>() as u64,
+                            index_buffer: Some(&index_buf),
+                            first_index: Some(0),
+                            transform_buffer: None,
+                            transform_buffer_offset: None,
+                        },
+                    ]),
+                },
+            ],
             iter::once(&tlas_package),
         );
 
@@ -270,6 +314,7 @@ impl crate::framework::Example for Example {
             uniforms,
             uniform_buf,
             blas,
+            blas_with_one_too_much_triangles,
             tlas_package,
             pipeline,
             bind_group,
@@ -311,6 +356,7 @@ impl crate::framework::Example for Example {
             for x in 0..side_count {
                 for y in 0..side_count {
                     let instance = self.tlas_package.index_mut((x + y * side_count) as usize);
+                    let checker = (x ^ y) & 1 == 0;
 
                     let x = x as f32 / (side_count - 1) as f32;
                     let y = y as f32 / (side_count - 1) as f32;
@@ -334,7 +380,16 @@ impl crate::framework::Example for Example {
                         .try_into()
                         .unwrap();
 
-                    *instance = Some(wgpu::TlasInstance::new(&self.blas, transform, 0, 0xff));
+                    *instance = Some(wgpu::TlasInstance::new(
+                        if checker {
+                            &self.blas
+                        } else {
+                            &self.blas_with_one_too_much_triangles
+                        },
+                        transform,
+                        0,
+                        0xff,
+                    ));
                 }
             }
         }