Stop Vulkan generating validation error in build acceleration structures (#6282)

CHANGELOG.md

@@ -117,6 +117,7 @@ By @bradwerth [#6216](https://github.com/gfx-rs/wgpu/pull/6216).
 #### Vulkan
 
 - Vulkan debug labels assumed no interior nul byte. By @DJMcNab in [#6257](https://github.com/gfx-rs/wgpu/pull/6257)
+- Add `.index_type(vk::IndexType::NONE_KHR)` when creating `AccelerationStructureGeometryTrianglesDataKHR` in the raytraced triangle example to prevent a validation error. By @Vecvec in [#6282](https://github.com/gfx-rs/wgpu/pull/6282)
 
 ### Changes
 

wgpu-hal/examples/ray-traced-triangle/main.rs

@@ -205,7 +205,7 @@ struct Example<A: hal::Api> {
     uniform_buffer: A::Buffer,
     pipeline_layout: A::PipelineLayout,
     vertices_buffer: A::Buffer,
-    indices_buffer: A::Buffer,
+    indices_buffer: Option<A::Buffer>,
     texture: A::Texture,
     instances: [AccelerationStructureInstance; 3],
     instances_buffer: A::Buffer,
@@ -217,6 +217,18 @@ struct Example<A: hal::Api> {
 
 impl<A: hal::Api> Example<A> {
     fn init(window: &winit::window::Window) -> Result<Self, Box<dyn std::error::Error>> {
+        let mut index_buffer = false;
+
+        for arg in std::env::args() {
+            if arg == "index_buffer" {
+                index_buffer = true;
+            }
+        }
+
+        if index_buffer {
+            log::info!("using index buffer")
+        }
+
         let instance_desc = hal::InstanceDescriptor {
             name: "example",
             flags: wgt::InstanceFlags::default(),
@@ -420,14 +432,16 @@ impl<A: hal::Api> Example<A> {
             vertices_buffer
         };
 
-        let indices_buffer = unsafe {
+        let indices_buffer = if index_buffer {
+            unsafe {
                 let indices_buffer = device
                     .create_buffer(&hal::BufferDescriptor {
                         label: Some("indices buffer"),
                         size: indices_size_in_bytes as u64,
                         usage: hal::BufferUses::MAP_WRITE
                             | hal::BufferUses::BOTTOM_LEVEL_ACCELERATION_STRUCTURE_INPUT,
-                    memory_flags: hal::MemoryFlags::TRANSIENT | hal::MemoryFlags::PREFER_COHERENT,
+                        memory_flags: hal::MemoryFlags::TRANSIENT
+                            | hal::MemoryFlags::PREFER_COHERENT,
                     })
                     .unwrap();
 
@@ -442,7 +456,10 @@ impl<A: hal::Api> Example<A> {
                 device.unmap_buffer(&indices_buffer);
                 assert!(mapping.is_coherent);
 
-            indices_buffer
+                Some((indices_buffer, indices.len()))
+            }
+        } else {
+            None
         };
 
         let blas_triangles = vec![hal::AccelerationStructureTriangles {
@@ -451,12 +468,15 @@ impl<A: hal::Api> Example<A> {
             vertex_format: wgt::VertexFormat::Float32x3,
             vertex_count: vertices.len() as u32,
             vertex_stride: 3 * 4,
-            indices: Some(hal::AccelerationStructureTriangleIndices {
-                buffer: Some(&indices_buffer),
+            indices: indices_buffer.as_ref().map(|(buf, len)| {
+                hal::AccelerationStructureTriangleIndices {
+                    buffer: Some(buf),
                     format: wgt::IndexFormat::Uint32,
                     offset: 0,
-                count: indices.len() as u32,
+                    count: *len as u32,
+                }
             }),
+
             transform: None,
             flags: hal::AccelerationStructureGeometryFlags::OPAQUE,
         }];
@@ -800,7 +820,7 @@ impl<A: hal::Api> Example<A> {
             tlas,
             scratch_buffer,
             time: 0.0,
-            indices_buffer,
+            indices_buffer: indices_buffer.map(|(buf, _)| buf),
             vertices_buffer,
             uniform_buffer,
             texture_view,
@@ -1026,7 +1046,9 @@ impl<A: hal::Api> Example<A> {
             self.device.destroy_bind_group(self.bind_group);
             self.device.destroy_buffer(self.scratch_buffer);
             self.device.destroy_buffer(self.instances_buffer);
-            self.device.destroy_buffer(self.indices_buffer);
+            if let Some(buffer) = self.indices_buffer {
+                self.device.destroy_buffer(buffer);
+            }
             self.device.destroy_buffer(self.vertices_buffer);
             self.device.destroy_buffer(self.uniform_buffer);
             self.device.destroy_acceleration_structure(self.tlas);

wgpu-hal/src/vulkan/command.rs

@@ -503,6 +503,9 @@ impl crate::CommandEncoder for super::CommandEncoder {
                     for triangles in in_geometries {
                         let mut triangle_data =
                             vk::AccelerationStructureGeometryTrianglesDataKHR::default()
+                                // IndexType::NONE_KHR is not set by default (due to being provided by VK_KHR_acceleration_structure) but unless there is an
+                                // index buffer we need to have IndexType::NONE_KHR as our index type.
+                                .index_type(vk::IndexType::NONE_KHR)
                                 .vertex_data(vk::DeviceOrHostAddressConstKHR {
                                     device_address: get_device_address(triangles.vertex_buffer),
                                 })