add utilities to get TLAS instance size from type and encode the type in a Device or Host reference

Author: devsh

include/nbl/asset/IAccelerationStructure.h

@@ -139,10 +139,12 @@ class IBottomLevelAccelerationStructure : public AccelerationStructure
 // forward declare for `static_assert`
 class ICPUBottomLevelAccelerationStructure;
 
+// TODO: maybe we should introduce a base class so that flags and Instance declarations aren't doubled up 
 template<class AccelerationStructure>
 class ITopLevelAccelerationStructure : public AccelerationStructure
 {
 		static_assert(std::is_base_of_v<IAccelerationStructure,AccelerationStructure>);
+
 	public:
 		inline bool isBLAS() const override {return false;}
 
@@ -246,6 +248,22 @@ class ITopLevelAccelerationStructure : public AccelerationStructure
 			SRT_MOTION
 		};
 
+		static uint16_t getInstanceSize(const INSTANCE_TYPE type)
+		{
+			switch (type)
+			{
+				case INSTANCE_TYPE::SRT_MOTION:
+					return sizeof(SRTMotionInstance<ptrdiff_t>);
+					break;
+				case INSTANCE_TYPE::MATRIX_MOTION:
+					return sizeof(MatrixMotionInstance<ptrdiff_t>);
+					break;
+				default:
+					break;
+			}
+			return sizeof(StaticInstance<ptrdiff_t>);
+		}
+
 	protected:
 		using AccelerationStructure::AccelerationStructure;
 		virtual ~ITopLevelAccelerationStructure() = default;

include/nbl/video/IGPUAccelerationStructure.h

@@ -483,6 +483,41 @@ class IGPUTopLevelAccelerationStructure : public asset::ITopLevelAccelerationStr
 		using DeviceBuildInfo = BuildInfo<IGPUBuffer>;
 		using HostBuildInfo = BuildInfo<asset::ICPUBuffer>;
 
+		static inline auto encodeTypeInRef(const INSTANCE_TYPE type, IGPUBottomLevelAccelerationStructure::device_op_ref_t ref)
+		{
+			// aligned to 16 bytes as per the spec
+			assert(ref.deviceAddress%16==0);
+			switch (type)
+			{
+				case INSTANCE_TYPE::SRT_MOTION:
+					ref.deviceAddress += 2;
+					break;
+				case INSTANCE_TYPE::MATRIX_MOTION:
+					ref.deviceAddress += 1;
+					break;
+				default:
+					break;
+			}
+			return ref;
+		}
+		static inline auto encodeTypeInRef(const INSTANCE_TYPE type, IGPUBottomLevelAccelerationStructure::host_op_ref_t ref)
+		{
+			// aligned to 16 bytes as per the spec
+			assert(ref.apiHandle%16==0);
+			switch (type)
+			{
+				case INSTANCE_TYPE::SRT_MOTION:
+					ref.apiHandle += 2;
+					break;
+				case INSTANCE_TYPE::MATRIX_MOTION:
+					ref.apiHandle += 1;
+					break;
+				default:
+					break;
+			}
+			return ref;
+		}
+
 		//! BEWARE, OUR RESOURCE LIFETIME TRACKING DOES NOT WORK ACROSS TLAS->BLAS boundaries with these types of BLAS references!
 		using DeviceInstance = Instance<IGPUBottomLevelAccelerationStructure::device_op_ref_t>;
 		using HostInstance = Instance<IGPUBottomLevelAccelerationStructure::host_op_ref_t>;