uniform vec3 u_noiseTextureDimensions;
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uniform float u_noiseDetail;
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uniform vec3 u_noiseOffset;
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varying vec2 v_position;
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float textureSliceWidth = u_noiseTextureDimensions.x;
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float inverseNoiseTextureRows = u_noiseTextureDimensions.z;
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float wrap(float value, float rangeLength) {
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if(value < 0.0) {
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float absValue = abs(value);
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float modValue = mod(absValue, rangeLength);
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return mod(rangeLength - modValue, rangeLength);
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}
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return mod(value, rangeLength);
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}
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vec3 wrapVec(vec3 value, float rangeLength) {
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return vec3(wrap(value.x, rangeLength),
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wrap(value.y, rangeLength),
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wrap(value.z, rangeLength));
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}
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vec3 random3(vec3 p) {
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float dot1 = dot(p, vec3(127.1, 311.7, 932.8));
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float dot2 = dot(p, vec3(269.5, 183.3, 421.4));
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return fract(vec3(sin(dot1 - dot2), cos(dot1 * dot2), dot1 * dot2));
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}
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// Frequency corresponds to cell size.
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// The higher the frequency, the smaller the cell size.
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vec3 getWorleyCellPoint(vec3 centerCell, vec3 offset, float freq) {
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vec3 cell = centerCell + offset;
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cell = wrapVec(cell, textureSliceWidth / u_noiseDetail);
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cell += floor(u_noiseOffset / u_noiseDetail);
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vec3 p = offset + random3(cell);
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return p;
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}
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float worleyNoise(vec3 p, float freq) {
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vec3 centerCell = floor(p * freq);
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vec3 pointInCell = fract(p * freq);
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float shortestDistance = 1000.0;
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for(float z = -1.0; z <= 1.0; z++) {
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for(float y = -1.0; y <= 1.0; y++) {
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for(float x = -1.0; x <= 1.0; x++) {
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vec3 offset = vec3(x, y, z);
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vec3 point = getWorleyCellPoint(centerCell, offset, freq);
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float distance = length(pointInCell - point);
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if(distance < shortestDistance) {
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shortestDistance = distance;
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}
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}
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}
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}
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return shortestDistance;
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}
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const float MAX_FBM_ITERATIONS = 10.0;
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float worleyFBMNoise(vec3 p, float octaves, float scale) {
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float noise = 0.0;
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float freq = 1.0;
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float persistence = 0.625;
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for(float i = 0.0; i < MAX_FBM_ITERATIONS; i++) {
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if(i >= octaves) {
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break;
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}
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noise += worleyNoise(p * scale, freq * scale) * persistence;
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persistence *= 0.5;
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freq *= 2.0;
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}
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return noise;
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}
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void main() {
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float x = mod(v_position.x, textureSliceWidth);
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float y = mod(v_position.y, textureSliceWidth);
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float sliceRow = floor(v_position.y / textureSliceWidth);
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float z = floor(v_position.x / textureSliceWidth) + sliceRow * inverseNoiseTextureRows * textureSliceWidth;
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vec3 position = vec3(x, y, z);
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position /= u_noiseDetail;
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float worley0 = clamp(worleyFBMNoise(position, 3.0, 1.0), 0.0, 1.0);
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float worley1 = clamp(worleyFBMNoise(position, 3.0, 2.0), 0.0, 1.0);
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float worley2 = clamp(worleyFBMNoise(position, 3.0, 3.0), 0.0, 1.0);
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gl_FragColor = vec4(worley0, worley1, worley2, 1.0);
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}
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