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float2 EyeToSourceUVScale;
float2 EyeToSourceUVOffset;
float4x4 EyeRotationStart;
float4x4 EyeRotationEnd;
float2 TimewarpTexCoordToWarpedPos(float2 inTexCoord, float4x4 rotMat)
{
// Vertex inputs are in TanEyeAngle space for the R,G,B channels (i.e. after chromatic aberration and distortion).
// These are now "real world" vectors in direction (x,y,1) relative to the eye of the HMD.
// Apply the 3x3 timewarp rotation to these vectors.
float3 transformed = float3( mul ( rotMat, float4(inTexCoord,1,1) ).xyz);
// Project them back onto the Z=1 plane of the rendered images.
float2 flattened = transformed.xy / transformed.z;
// Scale them into ([0,0.5],[0,1]) or ([0.5,0],[0,1]) UV lookup space (depending on eye)
return flattened * EyeToSourceUVScale + EyeToSourceUVOffset;
}
void main(in float2 Position : POSITION,
in float4 Color : COLOR0,
in float2 TexCoord0 : TEXCOORD0,
out float4 oPosition : SV_Position,
out float1 oColor : COLOR,
out float2 oTexCoord0 : TEXCOORD0)
{
oPosition.x = Position.x;
oPosition.y = Position.y;
oPosition.z = 0.5;
oPosition.w = 1.0;
float timewarpLerpFactor = Color.a;
float4x4 lerpedEyeRot = lerp(EyeRotationStart, EyeRotationEnd, timewarpLerpFactor);
// Warped positions are a bit more involved, hence a separate function
oTexCoord0 = TimewarpTexCoordToWarpedPos(TexCoord0, lerpedEyeRot);
oColor = Color.r; // Used for vignette fade.
}
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