42 lines
2.3 KiB
HLSL
42 lines
2.3 KiB
HLSL
// Both functions below are called from outside FEATURES_GRAPH_VERTEX, so the two terrain pass
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// templates include this file unconditionally, after the pass structs. Do not move it behind the
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// graphVertex feature gate. Keep this comment free of the template command character as well: the
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// preprocessor reads commands inside comments and splices an error marker into the shader.
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void TerrainVaryingGeneration(inout Attributes input, inout Varyings output)
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{
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float4 positionOS = float4(input.positionOS, 1.0);
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#if defined(VARYINGS_NEED_TEXCOORD0) && defined(ATTRIBUTES_NEED_NORMAL)
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TerrainInstancing(positionOS, input.normalOS, input.uv0.xy);
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#elif defined(VARYINGS_NEED_TEXCOORD0)
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float3 normal = float3(0, 0, 0);
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TerrainInstancing(positionOS, normal, input.uv0.xy);
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#elif defined(ATTRIBUTES_NEED_NORMAL)
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TerrainInstancing(positionOS, input.normalOS);
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#else
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TerrainInstancing(positionOS);
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#endif
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input.positionOS = positionOS.xyz;
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#if defined(VARYINGS_NEED_TEXCOORD0) && defined(UNIVERSAL_TERRAIN_SPLAT01)
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output.uvSplat01.xy = TRANSFORM_TEX(input.uv0, _Splat0);
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output.uvSplat01.zw = TRANSFORM_TEX(input.uv0, _Splat1);
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#endif
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#if defined(VARYINGS_NEED_TEXCOORD0) && defined(UNIVERSAL_TERRAIN_SPLAT23)
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output.uvSplat23.xy = TRANSFORM_TEX(input.uv0, _Splat2);
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output.uvSplat23.zw = TRANSFORM_TEX(input.uv0, _Splat3);
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#endif
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}
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float4 ConstructTerrainTangent(float3 normal, float3 positiveZ)
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{
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// Consider a flat terrain. It should have tangent be (1, 0, 0) and bitangent be (0, 0, 1) as the UV of the terrain grid mesh is a scale of the world XZ position.
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// In CreateTangentToWorld function (in SpaceTransform.hlsl), it is cross(normal, tangent) * sgn for the bitangent vector.
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// It is not true in a left-handed coordinate system for the terrain bitangent, if we provide 1 as the tangent.w. It would produce (0, 0, -1) instead of (0, 0, 1).
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// Also terrain's tangent calculation was wrong in a left handed system because cross((0,0,1), terrainNormalOS) points to the wrong direction as negative X.
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// Therefore all the 4 xyzw components of the tangent needs to be flipped to correct the tangent frame.
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// (See TerrainLitData.hlsl - GetSurfaceAndBuiltinData)
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float3 tangent = cross(normal, positiveZ);
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return float4(tangent, -1);
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}
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