Duckstation/data/resources/shaders/reshade/Shaders/TriDither.fxh

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////////////////////////////////////////////////////////////////////////////////
// Triangular Dither //
// By The Sandvich Maker //
// Ported to ReShade by TreyM //
////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
// //
// Usage: //
// Include this file in your shader like so: #include "TriDither.fx" //
// //
// For shader developers, use this syntax to do a function call in your //
// code as the last thing before exiting a given shader. You should dither //
// anytime data is going to be truncated to a lower bitdepth. Color input //
// must be a float3 value. //
// //
// input.rgb += TriDither(input.rgb, uv, bits); //
// //
// "bits" is an integer number that determines the bit depth //
// being dithered to. Usually 8, sometimes 10 //
// You can automate this by letting Reshade decide like so: //
// //
// input += TriDither(input, uv, BUFFER_COLOR_BIT_DEPTH); //
// //
// Manual setup looks something like this for an 8-bit backbuffer: //
// //
// input.rgb += TriDither(input.rgb, uv, 8); //
// //
////////////////////////////////////////////////////////////////////////////////
uniform float DitherTimer < source = "timer"; >;
#define remap(v, a, b) (((v) - (a)) / ((b) - (a)))
float rand21(float2 uv)
{
float2 noise = frac(sin(dot(uv, float2(12.9898, 78.233) * 2.0)) * 43758.5453);
return (noise.x + noise.y) * 0.5;
}
float rand11(float x)
{
return frac(x * 0.024390243);
}
float permute(float x)
{
return ((34.0 * x + 1.0) * x) % 289.0;
}
float3 TriDither(float3 color, float2 uv, int bits)
{
float bitstep = exp2(bits) - 1.0;
float lsb = 1.0 / bitstep;
float lobit = 0.5 / bitstep;
float hibit = (bitstep - 0.5) / bitstep;
float3 m = float3(uv, rand21(uv + (DitherTimer * 0.001))) + 1.0;
float h = permute(permute(permute(m.x) + m.y) + m.z);
float3 noise1, noise2;
noise1.x = rand11(h); h = permute(h);
noise2.x = rand11(h); h = permute(h);
noise1.y = rand11(h); h = permute(h);
noise2.y = rand11(h); h = permute(h);
noise1.z = rand11(h); h = permute(h);
noise2.z = rand11(h);
float3 lo = saturate(remap(color.xyz, 0.0, lobit));
float3 hi = saturate(remap(color.xyz, 1.0, hibit));
float3 uni = noise1 - 0.5;
float3 tri = noise1 - noise2;
return lerp(uni, tri, min(lo, hi)) * lsb;
}