mirror of
https://github.com/libretro/RetroArch
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67 lines
1.9 KiB
GLSL
67 lines
1.9 KiB
GLSL
#version 310 es
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precision highp float;
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layout(std140, set = 0, binding = 0) uniform UBO
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{
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float time;
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} constants;
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layout(location = 0) out vec4 FragColor;
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vec2 res = vec2(1920*3, 1080*3);
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// High quality = larger patterns
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// quality * 84 is the number of seconds in a loop
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float quality = 8.0;
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float Cellular2D(vec2 P) {
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// https://github.com/BrianSharpe/Wombat/blob/master/Cellular2D.glsl
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vec2 Pi = floor(P);
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vec2 Pf = P - Pi;
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vec2 Pt = vec2( Pi.x, Pi.y + 1.0 );
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Pt = Pt - floor(Pt * ( 1.0 / 71.0 )) * 71.0;
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Pt += vec2( 26.0, 161.0 ).xy;
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Pt *= Pt;
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Pt = Pt.xy * Pt.yx;
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float hash_x = fract( Pt * ( 1.0 / 951.135664 ) ).x * 2.0 - 1.0;
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float hash_y = fract( Pt * ( 1.0 / 642.949883 ) ).y * 2.0 - 1.0;
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const float JITTER_WINDOW = 0.25;
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hash_x = ( ( hash_x * hash_x * hash_x ) - sign( hash_x ) ) * JITTER_WINDOW;
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hash_y = ( ( hash_y * hash_y * hash_y ) - sign( hash_y ) ) * JITTER_WINDOW;
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vec2 dd = vec2(Pf.x - hash_x, Pf.y - hash_y);
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float d = dd.x * dd.x + dd.y * dd.y;
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return d * ( 1.0 / 1.125 );
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}
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float snow(vec2 pos, float time, float scale) {
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// add wobble
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pos.x += cos(pos.y*4.0 + time*3.14159*2.0 + 1.0/scale)/(8.0/scale);
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// add gravity
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pos += time*scale*vec2(-0.5, 1.0);
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return max(
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1.0 - Cellular2D(mod(pos/scale, scale*quality)*16.0)*1024.0,
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0.0
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) * (scale*0.5 + 0.5);
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}
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void main()
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{
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float winscale = max(res.x, res.y);
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float tim = mod(constants.time/800.0, 84.0*quality);
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vec2 pos = gl_FragCoord.xy/winscale;
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float a = 0.0;
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// Each of these is a layer of snow
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// Remove some for better performance
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// Changing the scale (3rd value) will mess with the looping
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a += snow(pos, tim, 1.0);
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a += snow(pos, tim, 0.7);
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a += snow(pos, tim, 0.6);
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a += snow(pos, tim, 0.5);
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a += snow(pos, tim, 0.4);
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a += snow(pos, tim, 0.3);
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a += snow(pos, tim, 0.25);
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a += snow(pos, tim, 0.125);
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a = a * min(pos.y*4.0, 1.0);
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FragColor = vec4(1.0, 1.0, 1.0, a);
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}
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