75 lines
1.8 KiB
GLSL
75 lines
1.8 KiB
GLSL
#version 310 es
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precision mediump float;
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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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vec2 OutputSize;
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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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const float baseScale = 3.5; // [1.0 .. 10.0]
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const float density = 0.7; // [0.01 .. 1.0]
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const float speed = 0.25; // [0.1 .. 1.0]
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float rand(vec2 co)
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{
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return fract(sin(dot(co.xy, vec2(12.9898, 78.233))) * 43758.5453);
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}
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float dist_func(vec2 distv)
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{
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float dist = sqrt((distv.x * distv.x) + (distv.y * distv.y)) * (40.0 / baseScale);
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dist = clamp(dist, 0.0, 1.0);
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return cos(dist * (3.14159265358 * 0.5)) * 0.5;
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}
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float random_dots(vec2 co)
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{
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float part = 1.0 / 20.0;
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vec2 cd = floor(co / part);
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float p = rand(cd);
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if (p > 0.005 * (density * 40.0))
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return 0.0;
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vec2 dpos = (vec2(fract(p * 2.0) , p) + vec2(2.0, 2.0)) * 0.25;
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vec2 cellpos = fract(co / part);
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vec2 distv = (cellpos - dpos);
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return dist_func(distv);
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}
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float snow(vec2 pos, float time, float scale)
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{
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// add wobble
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pos.x += cos(pos.y * 1.2 + time * 3.14159 * 2.0 + 1.0 / scale) / (8.0 / scale) * 4.0;
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// add gravity
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pos += time * scale * vec2(-0.5, 1.0) * 4.0;
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return random_dots(pos / scale) * (scale * 0.5 + 0.5);
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}
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void main(void)
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{
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float tim = constants.time * 0.4 * speed;
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vec2 pos = gl_FragCoord.xy / constants.OutputSize.xx;
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pos.y = 1.0 - pos.y; // Flip Y
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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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