74 lines
2.5 KiB
GLSL
74 lines
2.5 KiB
GLSL
// adapted by Alex Sherwin for Ghostty from https://www.shadertoy.com/view/lljGDt
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#define BLACK_BLEND_THRESHOLD .4
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float hash21(vec2 p) {
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p = fract(p * vec2(233.34, 851.73));
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p += dot(p, p + 23.45);
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return fract(p.x * p.y);
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}
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float rayStrength(vec2 raySource, vec2 rayRefDirection, vec2 coord, float seedA, float seedB, float speed)
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{
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vec2 sourceToCoord = coord - raySource;
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float cosAngle = dot(normalize(sourceToCoord), rayRefDirection);
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// Add subtle dithering based on screen coordinates
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float dither = hash21(coord) * 0.015 - 0.0075;
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float ray = clamp(
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(0.45 + 0.15 * sin(cosAngle * seedA + iTime * speed)) +
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(0.3 + 0.2 * cos(-cosAngle * seedB + iTime * speed)) + dither,
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0.0, 1.0);
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// Smoothstep the distance falloff
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float distFade = smoothstep(0.0, iResolution.x, iResolution.x - length(sourceToCoord));
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return ray * mix(0.5, 1.0, distFade);
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}
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void mainImage( out vec4 fragColor, in vec2 fragCoord )
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{
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vec2 uv = fragCoord.xy / iResolution.xy;
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uv.y = 1.0 - uv.y;
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vec2 coord = vec2(fragCoord.x, iResolution.y - fragCoord.y);
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// Set the parameters of the sun rays
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vec2 rayPos1 = vec2(iResolution.x * 0.7, iResolution.y * 1.1);
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vec2 rayRefDir1 = normalize(vec2(1.0, 0.116));
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float raySeedA1 = 36.2214;
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float raySeedB1 = 21.11349;
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float raySpeed1 = 1.1;
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vec2 rayPos2 = vec2(iResolution.x * 0.8, iResolution.y * 1.2);
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vec2 rayRefDir2 = normalize(vec2(1.0, -0.241));
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const float raySeedA2 = 22.39910;
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const float raySeedB2 = 18.0234;
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const float raySpeed2 = 0.9;
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// Calculate the colour of the sun rays on the current fragment
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vec4 rays1 =
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vec4(1.0, 1.0, 1.0, 0.0) *
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rayStrength(rayPos1, rayRefDir1, coord, raySeedA1, raySeedB1, raySpeed1);
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vec4 rays2 =
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vec4(1.0, 1.0, 1.0, 0.0) *
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rayStrength(rayPos2, rayRefDir2, coord, raySeedA2, raySeedB2, raySpeed2);
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vec4 col = rays1 * 0.5 + rays2 * 0.4;
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// Attenuate brightness towards the bottom, simulating light-loss due to depth.
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// Give the whole thing a blue-green tinge as well.
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float brightness = 1.0 - (coord.y / iResolution.y);
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col.r *= 0.05 + (brightness * 0.8);
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col.g *= 0.15 + (brightness * 0.6);
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col.b *= 0.3 + (brightness * 0.5);
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vec2 termUV = fragCoord.xy / iResolution.xy;
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vec4 terminalColor = texture(iChannel0, termUV);
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float alpha = step(length(terminalColor.rgb), BLACK_BLEND_THRESHOLD);
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vec3 blendedColor = mix(terminalColor.rgb * 1.0, col.rgb * 0.3, alpha);
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fragColor = vec4(blendedColor, terminalColor.a);
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}
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