remove the INSTANCE_DATA_IS_POINTERS_TYPE_ENCODED_LSB flag, moveit as a bool to IGPUTopLevelAccelerationStructure

The ICPUTopLevelAccelerationStructure had no business knowing about encoding of input instance data during a Device build.

Author: devsh

include/nbl/asset/IAccelerationStructure.h

@@ -154,8 +154,6 @@ class ITopLevelAccelerationStructure : public AccelerationStructure
 			PREFER_FAST_TRACE_BIT = 0x1u<<2u,
 			PREFER_FAST_BUILD_BIT = 0x1u<<3u,
 			LOW_MEMORY_BIT = 0x1u<<4u,
-			// Synthetic flag we use to indicate `VkAccelerationStructureGeometryInstancesDataKHR::arrayOfPointers`
-			INSTANCE_DATA_IS_POINTERS_TYPE_ENCODED_LSB = 0x1u<<5u, // this flag really shouldn't be settable outside of `video::IGPU`
 			// Provided by VK_NV_ray_tracing_motion_blur, but we always override and deduce from creation flag because of
 			// https://registry.khronos.org/vulkan/specs/1.3-extensions/html/vkspec.html#VUID-VkAccelerationStructureBuildGeometryInfoKHR-dstAccelerationStructure-04927
 			//MOTION_BIT = 0x1u<<5u,
@@ -237,7 +235,7 @@ class ITopLevelAccelerationStructure : public AccelerationStructure
 			static_assert(alignof(Instance<blas_ref_t>)==8ull);
 		};
 
-		// enum for distinguishing unions of Instance Types when there is no `INSTANCE_DATA_IS_POINTERS_TYPE_ENCODED_LSB` in build flags
+		// enum for distinguishing unions of Instance Types when using a polymorphic instance
 		enum class INSTANCE_TYPE : uint32_t
 		{
 			// StaticInstance

include/nbl/asset/ICPUAccelerationStructure.h

@@ -311,8 +311,6 @@ class ICPUTopLevelAccelerationStructure final : public ITopLevelAccelerationStru
 			if(!isMutable())
 				return;
 			m_buildFlags = buildFlags;
-			// we always clear this flag as we always store instances as polymorphic for ICPUTopLevelAccelerationStructure
-			m_buildFlags &= ~BUILD_FLAGS::INSTANCE_DATA_IS_POINTERS_TYPE_ENCODED_LSB;
 		}
 
 		//

include/nbl/video/IGPUAccelerationStructure.h

@@ -411,7 +411,7 @@ class IGPUTopLevelAccelerationStructure : public asset::ITopLevelAccelerationStr
 						if (buildRangeInfo.instanceCount>dstAS->getMaxInstanceCount())
 							return false;
 
-						const bool arrayOfPointers = buildFlags.hasFlags(BUILD_FLAGS::INSTANCE_DATA_IS_POINTERS_TYPE_ENCODED_LSB);
+						const bool arrayOfPointers = instanceDataTypeEncodedInPointersLSB;
 						constexpr bool HostBuild = std::is_same_v<BufferType,asset::ICPUBuffer>;
 						// I'm not gonna do the `std::conditional_t<HostBuild,,>` to get the correct Instance struct type as they're the same size essentially
 						const size_t instanceSize = arrayOfPointers ? sizeof(void*):(
@@ -467,11 +467,13 @@ class IGPUTopLevelAccelerationStructure : public asset::ITopLevelAccelerationStr
 
 
 				core::bitflag<BUILD_FLAGS> buildFlags = BUILD_FLAGS::PREFER_FAST_BUILD_BIT;
+				// What we use to indicate `VkAccelerationStructureGeometryInstancesDataKHR::arrayOfPointers`
+				uint8_t instanceDataTypeEncodedInPointersLSB : 1 = false;
 				const IGPUTopLevelAccelerationStructure* srcAS = nullptr;
 				IGPUTopLevelAccelerationStructure* dstAS = nullptr;
-				// depending on the presence certain bits in `buildFlags` this buffer will be filled with:
+				// depending on value of certain build info members this buffer will be filled with:
 				// - addresses to `StaticInstance`, `MatrixMotionInstance`, `SRTMotionInstance` packed in upper 60 bits 
-				//   and struct type in lower 4 bits if and only if `buildFlags.hasFlags(INSTANCE_DATA_IS_POINTERS_TYPE_ENCODED_LSB)`, otherwise:
+				//   and struct type in lower 4 bits if and only if `instanceDataTypeEncodedInPointersLSB`, otherwise:
 				//	+ an array of `PolymorphicInstance` if our `SCreationParams::flags.hasFlags(MOTION_BIT)`, otherwise
 				//	+ an array of `StaticInstance`
 				asset::SBufferBinding<const BufferType> instanceData = {};
@@ -482,7 +484,6 @@ class IGPUTopLevelAccelerationStructure : public asset::ITopLevelAccelerationStr
 		using HostBuildInfo = BuildInfo<asset::ICPUBuffer>;
 
 		//! BEWARE, OUR RESOURCE LIFETIME TRACKING DOES NOT WORK ACROSS TLAS->BLAS boundaries with these types of BLAS references!
-		// TODO: Investigate `EXT_private_data` to be able to go ` -> IGPUBottomLevelAccelerationStructure` on Host Builds
 		using DeviceInstance = Instance<IGPUBottomLevelAccelerationStructure::device_op_ref_t>;
 		using HostInstance = Instance<IGPUBottomLevelAccelerationStructure::host_op_ref_t>;
 		static_assert(sizeof(DeviceInstance)==sizeof(HostInstance));

src/nbl/video/CVulkanAccelerationStructure.h

@@ -172,7 +172,7 @@ void getVkASGeometryFrom(const IGPUTopLevelAccelerationStructure::BuildInfo<Buff
 {
 	outBase = {VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_KHR,nullptr,VK_GEOMETRY_TYPE_INSTANCES_KHR};
 	outBase.geometry.instances = {VK_STRUCTURE_TYPE_ACCELERATION_STRUCTURE_GEOMETRY_INSTANCES_DATA_KHR,nullptr};
-	outBase.geometry.instances.arrayOfPointers = info.buildFlags.hasFlags(IGPUTopLevelAccelerationStructure::BUILD_FLAGS::INSTANCE_DATA_IS_POINTERS_TYPE_ENCODED_LSB);
+	outBase.geometry.instances.arrayOfPointers = info.instanceDataTypeEncodedInPointersLSB;
 	outBase.geometry.instances.data = QueryOnly ? NullAddress:getVkDeviceOrHostAddress<const BufferType>(info.instanceData);
 	// no "geometry flags" are valid for all instances!
 	outBase.flags = static_cast<VkGeometryFlagsKHR>(0u);