Implements Device::tlas_instance_to_bytes().

Author: Lichtso

wgpu-hal/Cargo.toml

@@ -74,6 +74,7 @@ metal = [
     "naga/msl-out",
     "dep:arrayvec",
     "dep:block2",
+    "dep:bytemuck",
     "dep:hashbrown",
     "dep:libc",
     "dep:log",
@@ -278,6 +279,7 @@ mach-dxcompiler-rs = { workspace = true, optional = true }
 [target.'cfg(target_vendor = "apple")'.dependencies]
 # Backend: Metal
 block2 = { workspace = true, optional = true }
+bytemuck = { workspace = true, optional = true }
 objc2 = { workspace = true, optional = true }
 objc2-core-foundation = { workspace = true, optional = true }
 objc2-foundation = { workspace = true, optional = true }

wgpu-hal/src/metal/device.rs

@@ -2,18 +2,21 @@ use alloc::{borrow::ToOwned as _, sync::Arc, vec::Vec};
 use core::{ptr::NonNull, sync::atomic};
 use std::{thread, time};
 
+use bytemuck::TransparentWrapper;
 use objc2::{
     msg_send,
     rc::{autoreleasepool, Retained},
     runtime::ProtocolObject,
 };
 use objc2_foundation::{ns_string, NSError, NSRange, NSString};
 use objc2_metal::{
-    MTLAccelerationStructure, MTLBuffer, MTLCaptureManager, MTLCaptureScope, MTLCommandBuffer,
-    MTLCommandBufferStatus, MTLCompileOptions, MTLComputePipelineDescriptor,
-    MTLComputePipelineState, MTLCounterSampleBufferDescriptor, MTLCounterSet, MTLDepthClipMode,
-    MTLDepthStencilDescriptor, MTLDevice, MTLFunction, MTLLanguageVersion, MTLLibrary,
-    MTLMutability, MTLPipelineBufferDescriptorArray, MTLPixelFormat, MTLPrimitiveTopologyClass,
+    MTLAccelerationStructure, MTLAccelerationStructureInstanceOptions, MTLBuffer,
+    MTLCaptureManager, MTLCaptureScope, MTLCommandBuffer, MTLCommandBufferStatus,
+    MTLCompileOptions, MTLComputePipelineDescriptor, MTLComputePipelineState,
+    MTLCounterSampleBufferDescriptor, MTLCounterSet, MTLDepthClipMode, MTLDepthStencilDescriptor,
+    MTLDevice, MTLFunction, MTLIndirectAccelerationStructureInstanceDescriptor, MTLLanguageVersion,
+    MTLLibrary, MTLMutability, MTLPackedFloat3, MTLPackedFloat4x3,
+    MTLPipelineBufferDescriptorArray, MTLPixelFormat, MTLPrimitiveTopologyClass,
     MTLRenderPipelineDescriptor, MTLResource, MTLResourceID, MTLResourceOptions,
     MTLSamplerAddressMode, MTLSamplerDescriptor, MTLSamplerMipFilter, MTLSamplerState, MTLSize,
     MTLStencilDescriptor, MTLStorageMode, MTLTexture, MTLTextureDescriptor, MTLTextureType,
@@ -1706,8 +1709,42 @@ impl crate::Device for super::Device {
         // self.counters.acceleration_structures.sub(1);
     }
 
-    fn tlas_instance_to_bytes(&self, _instance: TlasInstance) -> Vec<u8> {
-        unimplemented!()
+    fn tlas_instance_to_bytes(&self, instance: TlasInstance) -> Vec<u8> {
+        let temp = MTLIndirectAccelerationStructureInstanceDescriptor {
+            transformationMatrix: MTLPackedFloat4x3 {
+                columns: [
+                    MTLPackedFloat3 {
+                        x: instance.transform[0],
+                        y: instance.transform[4],
+                        z: instance.transform[8],
+                    },
+                    MTLPackedFloat3 {
+                        x: instance.transform[1],
+                        y: instance.transform[5],
+                        z: instance.transform[9],
+                    },
+                    MTLPackedFloat3 {
+                        x: instance.transform[2],
+                        y: instance.transform[6],
+                        z: instance.transform[10],
+                    },
+                    MTLPackedFloat3 {
+                        x: instance.transform[3],
+                        y: instance.transform[7],
+                        z: instance.transform[11],
+                    },
+                ],
+            },
+            options: MTLAccelerationStructureInstanceOptions::None,
+            mask: instance.mask as u32,
+            intersectionFunctionTableOffset: 0,
+            userID: instance.custom_data,
+            accelerationStructureID: unsafe { MTLResourceID::from_raw(instance.blas_address) },
+        };
+
+        wgt::bytemuck_wrapper!(unsafe struct Desc(MTLIndirectAccelerationStructureInstanceDescriptor));
+
+        bytemuck::bytes_of(&Desc::wrap(temp)).to_vec()
     }
 
     fn get_internal_counters(&self) -> wgt::HalCounters {