65 lines
2.0 KiB
Plaintext
65 lines
2.0 KiB
Plaintext
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precision highp float;
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// This shader governs the glyphs appearing in the rain.
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// It writes each glyph's state to the channels of a data texture:
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// R: symbol
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// G: age
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// B: unused
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// A: unused
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#define PI 3.14159265359
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uniform sampler2D previousSymbolState, raindropState;
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uniform float numColumns, numRows;
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uniform float time, tick, cycleFrameSkip;
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uniform float animationSpeed, cycleSpeed;
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uniform bool loops, showDebugView;
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uniform float glyphSequenceLength;
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// Helper functions for generating randomness, borrowed from elsewhere
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highp float randomFloat( const in vec2 uv ) {
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const highp float a = 12.9898, b = 78.233, c = 43758.5453;
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highp float dt = dot( uv.xy, vec2( a,b ) ), sn = mod( dt, PI );
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return fract(sin(sn) * c);
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}
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// Main function
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vec4 computeResult(float simTime, bool isFirstFrame, vec2 glyphPos, vec2 screenPos, vec4 previous, vec4 raindrop) {
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float previousSymbol = previous.r;
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float previousAge = previous.g;
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bool resetGlyph = isFirstFrame;
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if (loops) {
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resetGlyph = resetGlyph || raindrop.r <= 0.;
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}
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if (resetGlyph) {
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previousAge = randomFloat(screenPos + 0.5);
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previousSymbol = floor(glyphSequenceLength * randomFloat(screenPos));
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}
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float cycleSpeed = animationSpeed * cycleSpeed;
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float age = previousAge;
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float symbol = previousSymbol;
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if (mod(tick, cycleFrameSkip) == 0.) {
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age += cycleSpeed * cycleFrameSkip;
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if (age >= 1.) {
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symbol = floor(glyphSequenceLength * randomFloat(screenPos + simTime));
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age = fract(age);
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}
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}
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vec4 result = vec4(symbol, age, 0., 0.);
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return result;
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}
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void main() {
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float simTime = time * animationSpeed;
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bool isFirstFrame = tick <= 1.;
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vec2 glyphPos = gl_FragCoord.xy;
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vec2 screenPos = glyphPos / vec2(numColumns, numRows);
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vec4 previous = texture2D( previousSymbolState, screenPos );
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vec4 raindrop = texture2D( raindropState, screenPos );
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gl_FragColor = computeResult(simTime, isFirstFrame, glyphPos, screenPos, previous, raindrop);
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}
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