mirror of
https://github.com/italicsjenga/slang-shaders.git
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142 lines
3.7 KiB
Plaintext
142 lines
3.7 KiB
Plaintext
#version 450
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/*
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NES NTSC Color Decoder shader
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Ported from Bisqwit's C++ NES Palette Generator
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https://forums.nesdev.com/viewtopic.php?p=85060#p85060
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Use with Nestopia or FCEUmm libretro cores with the palette set to 'raw'.
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*/
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layout(std140, set = 0, binding = 0) uniform UBO
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{
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mat4 MVP;
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vec4 OutputSize;
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vec4 OriginalSize;
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vec4 SourceSize;
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uint FrameCount;
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} global;
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layout(push_constant) uniform Push
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{
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float nes_saturation;
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float nes_hue;
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float nes_contrast;
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float nes_brightness;
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float nes_gamma;
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} params;
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#pragma parameter nes_saturation "Saturation" 1.0 0.0 5.0 0.05
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#pragma parameter nes_hue "Hue" 0.0 -360.0 360.0 1.0
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#pragma parameter nes_contrast "Contrast" 1.0 0.0 2.0 0.05
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#pragma parameter nes_brightness "Brightness" 1.0 0.0 2.0 0.05
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#pragma parameter nes_gamma "Gamma" 1.8 1.0 2.5 0.05
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#define saturation params.nes_saturation
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#define hue params.nes_hue
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#define contrast params.nes_contrast
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#define brightness params.nes_brightness
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#define gamma params.nes_gamma
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bool wave (int p, int color)
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{
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return ((color + p + 8) % 12 < 6);
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}
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float gammafix (float f)
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{
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return f < 0.0 ? 0.0 : pow(f, 2.2 / gamma);
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}
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vec3 MakeRGBColor(int emphasis, int level, int color)
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{
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float y = 0.0;
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float i = 0.0;
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float q = 0.0;
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float r = 0.0;
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float g = 0.0;
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float b = 0.0;
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// Voltage levels, relative to synch voltage
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float black = 0.518;
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float white = 1.962;
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float attenuation = 0.746;
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const float levels[8] = float[] ( 0.350 , 0.518, 0.962, 1.550,
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1.094, 1.506, 1.962, 1.962);
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float low = levels[level + 4 * int(color == 0)];
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float high = levels[level + 4 * int(color < 13)];
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// Calculate the luma and chroma by emulating the relevant circuits:
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for(int p = 0; p < 12; p++) // 12 clock cycles per pixel.
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{
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// NES NTSC modulator (square wave between two voltage levels):
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float spot = wave(p, color) ? high : low;
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// De-emphasis bits attenuate a part of the signal:
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if ((bool(emphasis & 1) && wave(p, 12)) ||
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(bool(emphasis & 2) && wave(p, 4)) ||
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(bool(emphasis & 4) && wave(p, 8)))
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{
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spot *= attenuation;
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}
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// Normalize:
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float v = (spot - black) / (white - black);
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// Ideal TV NTSC demodulator:
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// Apply contrast/brightness
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v = (v - 0.5) * contrast + 0.5;
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v *= (brightness / 12.0);
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float hue_tweak = hue * 12.0 / 360.0;
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y += v;
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i += v * cos((3.141592653 / 6.0) * (p + hue_tweak) );
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q += v * sin((3.141592653 / 6.0) * (p + hue_tweak) );
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}
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i *= saturation;
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q *= saturation;
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// Convert YIQ into RGB according to a commonly used conversion matrix.
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r = clamp((1.0 * gammafix(y + 0.956 * i + 0.621 * q)), 0, 1.0);
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g = clamp((1.0 * gammafix(y + -0.272 * i + -0.647 * q)), 0, 1.0);
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b = clamp((1.0 * gammafix(y + -1.105 * i + 1.702 * q)), 0, 1.0);
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return vec3(r,g,b);
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}
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#pragma stage vertex
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layout(location = 0) in vec4 Position;
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layout(location = 1) in vec2 TexCoord;
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layout(location = 0) out vec2 vTexCoord;
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layout(location = 1) out float colorPhase;
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void main()
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{
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gl_Position = global.MVP * Position;
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vTexCoord = TexCoord;
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}
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#pragma stage fragment
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layout(location = 0) in vec2 vTexCoord;
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layout(location = 1) in float colorPhase;
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layout(location = 0) out vec4 FragColor;
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layout(set = 0, binding = 2) uniform sampler2D Source;
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void main()
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{
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vec4 c = texture(Source, vTexCoord.xy);
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// Extract the chroma, level, and emphasis from the normalized RGB triplet
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int color = int(floor((c.r * 15.0) + 0.5));
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int level = int(floor((c.g * 3.0) + 0.5));
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int emphasis = int(floor((c.b * 7.0) + 0.5));
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vec3 out_color = MakeRGBColor(emphasis, level, color);
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FragColor = vec4(out_color, 1.0);
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}
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