90 lines
2.5 KiB
HLSL
90 lines
2.5 KiB
HLSL
#include "Conversion.fxh"
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// technique from http://alex-charlton.com/posts/Dithering_on_the_GPU/
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uniform float3 palette[8];
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static const int paletteSize = 8;
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static const int indexMatrix4x4[16] =
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{
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0, 8, 2, 10,
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12, 4, 14, 6,
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3, 11, 1, 9,
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15, 7, 13, 5
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};
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float indexValue(float2 screenCoords)
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{
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int x = int(screenCoords.x % 4);
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int y = int(screenCoords.y % 4);
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return indexMatrix4x4[(x + y * 4)] / 16.0;
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}
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float hueDistance(float h1, float h2)
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{
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float diff = abs(h1 - h2);
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return min(abs(1.0 - diff), diff);
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}
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void closestColors(float hue, out float3 ret[2])
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{
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float3 closest = float3(-2, 0, 0);
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float3 secondClosest = float3(-2, 0, 0);
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float3 temp;
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for (int i = 0; i < paletteSize; i++)
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{
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temp = palette[i];
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float tempDistance = hueDistance(temp.x, hue);
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if (tempDistance < hueDistance(closest.x, hue))
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{
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secondClosest = closest;
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closest = temp;
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}
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else
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{
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if (tempDistance < hueDistance(secondClosest.x, hue))
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{
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secondClosest = temp;
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}
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}
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}
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ret[0] = closest;
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ret[1] = secondClosest;
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}
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float3 dither(float3 color, float2 screenCoords)
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{
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float3 colors[2];
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float3 hsl = RGBtoHSL(color);
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closestColors(hsl.x, colors);
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float3 closestColor = colors[0];
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float3 secondClosestColor = colors[1];
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float d = indexValue(screenCoords);
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float hueDiff = hueDistance(hsl.x, closestColor.x) / hueDistance(secondClosestColor.x, secondClosestColor.x);
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return HSLtoRGB(hueDiff < d ? closestColor : secondClosestColor);
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}
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// brightColor refers to undithered max color
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// float3 dither(float3 color, float3 brightColor, float2 screenCoords)
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// {
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// float brightHue = RGBtoHSL(brightColor.x);
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// float colorHue = RGBtoHSL(color.x);
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// float halfDistance = hueDistance(0.0, brightHue) / 2.0;
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// float3 closestColor = (colorHue < halfDistance) ? float3(0.0, 0.0, 0.0) : brightColor;
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// float3 secondClosestColor = brightColor - closestColor;
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// float d = indexValue(screenCoords);
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// float distance = abs(closestColor - color);
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// return (distance < d) ? closestColor : secondClosestColor;
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// }
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float3 dither(float color, float2 screenCoords) {
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float closestColor = (color < 0.5) ? 0 : 1;
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float secondClosestColor = 1 - closestColor;
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float d = indexValue(screenCoords);
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float distance = abs(closestColor - color);
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return (distance < d) ? closestColor : secondClosestColor;
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}
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