Remove objects with transmission from TLAS

We used to not trace them and now we do, but they don't have an alpha
tested texture (and they aren't currently rendered in the main pass!)

src/niagara.cpp

@@ -408,7 +408,7 @@ VkAccelerationStructureKHR buildTLAS(VkDevice device, Buffer& tlasBuffer, const
 		instance.instanceCustomIndex = i;
 		instance.mask = 1 << draw.postPass;
 		instance.flags = draw.postPass ? VK_GEOMETRY_INSTANCE_FORCE_NO_OPAQUE_BIT_KHR : VK_GEOMETRY_INSTANCE_FORCE_OPAQUE_BIT_KHR;
-		instance.accelerationStructureReference = blasAddresses[draw.meshIndex];
+		instance.accelerationStructureReference = draw.postPass <= 1 ? blasAddresses[draw.meshIndex] : 0;
 
 		memcpy(static_cast<VkAccelerationStructureInstanceKHR*>(instances.data) + i, &instance, sizeof(VkAccelerationStructureInstanceKHR));
 	}