ProjectArcade

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/*
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[configuration]
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[OptionRangeFloat]
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GUIName = Distortion amount
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OptionName = DISTORTION_FACTOR
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MinValue = 1.0
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MaxValue = 10.0
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StepAmount = 0.5
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DefaultValue = 4.0
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[OptionRangeFloat]
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GUIName = Eye Distance Offset
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OptionName = EYE_OFFSET
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MinValue = 0.0
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MaxValue = 10.0
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StepAmount = 0.25
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DefaultValue = 5.0
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[OptionRangeFloat]
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GUIName = Zoom adjustment
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OptionName = SIZE_ADJUST
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MinValue = 0.0
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MaxValue = 1.0
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StepAmount = 0.025
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DefaultValue = 0.5
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[OptionRangeFloat]
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GUIName = Aspect Ratio adjustment
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OptionName = ASPECT_ADJUST
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MinValue = 0.0
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MaxValue = 1.0
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StepAmount = 0.025
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DefaultValue = 0.5
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[/configuration]
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*/
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void main()
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{
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  // Base Cardboard distortion parameters
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  float factor = GetOption(DISTORTION_FACTOR) * 0.01f;
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  float ka = factor * 3.0f;
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  float kb = factor * 5.0f;
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  // size and aspect adjustment
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  float sizeAdjust = 1.0f - GetOption(SIZE_ADJUST) + 0.5f;
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  float aspectAdjustment = 1.25f - GetOption(ASPECT_ADJUST);
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  // offset centering per eye
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  float stereoOffset = GetOption(EYE_OFFSET) * 0.01f;
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  float offsetAdd;
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  // layer0 = left eye, layer1 = right eye
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  if (layer == 1)
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  {
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    offsetAdd = stereoOffset;
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  }
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  else
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  {
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    offsetAdd = 0.0 - stereoOffset;
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  }
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  // convert coordinates to NDC space
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  float2 fragPos = (GetCoordinates() - 0.5f - vec2(offsetAdd, 0.0f)) * 2.0f;
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  // Calculate the source location "radius" (distance from the centre of the viewport)
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  float destR = length(fragPos);
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  // find the radius multiplier
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  float srcR = destR * sizeAdjust + ( ka * pow(destR, 2.0) + kb * pow(destR, 4.0));
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  // Calculate the source vector (radial)
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  vec2 correctedRadial = normalize(fragPos) * srcR;
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  // fix aspect ratio
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  vec2 widenedRadial = correctedRadial * vec2(aspectAdjustment, 1.0f);
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  // Transform the coordinates (from [-1,1]^2 to [0, 1]^2)
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  vec2 uv = (widenedRadial/2.0f) + vec2(0.5f) + vec2(offsetAdd, 0.0f);
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  // Sample the texture at the source location
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  if(clamp(uv, 0.0, 1.0) != uv)
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  {
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    // black if beyond bounds
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    SetOutput(float4(0.0, 0.0, 0.0, 0.0));
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  }
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  else
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  {
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    SetOutput(SampleLocation(uv));
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  }
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}
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