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Basic approach is to add HLSL types FLWCScalar, FLWCMatrix, FLWCVector, etc. Inside shaders, absolute world space position values should be represented as FLWCVector3. Matrices that transform *into* absolute world space become FLWCMatrix. Matrices that transform *from* world space become FLWCInverseMatrix. Generally LWC values work by extending the regular 'float' value with an additional tile coordinate. Final tile size will be a trade-off between scale/accuracy; I'm using 256k for now, but may need to be adjusted. Value represented by a FLWCVector thus becomes V.Tile * TileSize + V.Offset. Most operations can be performed directly on LWC values. There are HLSL functions like LWCAdd, LWCSub, LWCMultiply, LWCDivide (operator overloading would be really nice here). The goal is to stay with LWC values for as long as needed, then convert to regular float values when possible. One thing that comes up a lot is working in translated (rather than absolute) world space. WorldSpace + View.PrevPreViewTranslation = TranslatedWorldspace. Except 'View.PrevPreViewTranslation' is now a FLWCVector3, and WorldSpace quantities should be as well. So that becomes LWCAdd(WorldSpace, View.PrevPreViewTranslation) = TranslatedWorldspace. Assuming that we're talking about a position that's "reasonably close" to the camera, it should be safe to convert the translated WS value to float. The 'tile' coordinate of the 2 LWC values should cancel out when added together in this case. I've done some work throughout the shader code to do this. Materials are fully supporting LWC-values as well. Projective texturing and vertex animation materials that I've tested work correctly even when positioned "far away" from the origin. Lots of work remains to fully convert all of our shader code. There's a function LWCHackToFloat(), which is a simple wrapper for LWCToFloat(). The idea of HackToFloat is to mark places that need further attention, where I'm simply converting absolute WS positions to float, to get shaders to compile. Shaders converted in this way should continue to work for all existing content (without LWC-scale values), but they will break if positions get too large. General overview of changed files: LargeWorldCoordinates.ush - This defines the FLWC types and operations GPUScene.cpp, SceneData.ush - Primitives add an extra 'float3' tile coordinate. Instance data is unchanged, so instances need to stay within single-precision range of the primitive origin. Could potentially split instances behind the scenes (I think) if we don't want this limitation HLSLMaterialDerivativeAutogen.cpp, HLSLMaterialTranslator.cpp, Preshader.cpp - Translated materials to use LWC values SceneView.cpp, SceneRelativeViewMatrices.cpp, ShaderCompiler.cpp, InstancedStereo.ush - View uniform buffer includes LWC values where appropriate #jira UE-117101 #rb arne.schober, Michael.Galetzka [CL 17787435 by Ben Ingram in ue5-main branch]
57 lines
1.8 KiB
Plaintext
57 lines
1.8 KiB
Plaintext
// Copyright Epic Games, Inc. All Rights Reserved.
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// Note: include at the end of vertex factories to provide default/dummy implementation of factory functions that are not supported OR that follow the standard pattern
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// E.g., if the VF implements the three flavours of VertexFactoryGetViewIndex, it should define VF_IMPLEMENTED_GET_VIEW_INDEX
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#ifndef VF_IMPLEMENTED_GET_VIEW_INDEX
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#define VF_IMPLEMENTED_GET_VIEW_INDEX
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uint VertexFactoryGetViewIndex(FVertexFactoryIntermediates Intermediates)
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{
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return Intermediates.SceneData.ViewIndex;
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}
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uint VertexFactoryGetInstanceIdLoadIndex(FVertexFactoryIntermediates Intermediates)
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{
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return Intermediates.SceneData.InstanceIdLoadIndex;
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}
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FLWCMatrix VertexFactoryGetLocalToWorld(FVertexFactoryIntermediates Intermediates)
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{
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return Intermediates.SceneData.InstanceData.LocalToWorld;
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}
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FLWCInverseMatrix VertexFactoryGetWorldToLocal(FVertexFactoryIntermediates Intermediates)
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{
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return Intermediates.SceneData.InstanceData.WorldToLocal;
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}
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#if POSITION_ONLY
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uint VertexFactoryGetViewIndex(FPositionOnlyVertexFactoryInput Input)
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{
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FSceneDataIntermediates SceneData = VF_GPUSCENE_GET_INTERMEDIATES(Input);
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return SceneData.ViewIndex;
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}
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uint VertexFactoryGetViewIndex(FPositionAndNormalOnlyVertexFactoryInput Input)
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{
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FSceneDataIntermediates SceneData = VF_GPUSCENE_GET_INTERMEDIATES(Input);
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return SceneData.ViewIndex;
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}
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uint VertexFactoryGetInstanceIdLoadIndex(FPositionOnlyVertexFactoryInput Input)
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{
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FSceneDataIntermediates SceneData = VF_GPUSCENE_GET_INTERMEDIATES(Input);
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return SceneData.InstanceIdLoadIndex;
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}
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uint VertexFactoryGetInstanceIdLoadIndex(FPositionAndNormalOnlyVertexFactoryInput Input)
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{
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FSceneDataIntermediates SceneData = VF_GPUSCENE_GET_INTERMEDIATES(Input);
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return SceneData.InstanceIdLoadIndex;
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}
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#endif // POSITION_ONLY
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#endif // VF_IMPLEMENTED_GET_VIEW_INDEX
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