uniform float u_radiusTS;
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varying vec2 v_textureCoordinates;
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vec2 rotate(vec2 p, vec2 direction)
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{
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return vec2(p.x * direction.x - p.y * direction.y, p.x * direction.y + p.y * direction.x);
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}
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vec4 addBurst(vec2 position, vec2 direction, float lengthScalar)
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{
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vec2 rotatedPosition = rotate(position, direction) * vec2(25.0, 0.75);
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float radius = length(rotatedPosition) * lengthScalar;
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float burst = 1.0 - smoothstep(0.0, 0.55, radius);
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return vec4(burst);
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}
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void main()
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{
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float lengthScalar = 2.0 / sqrt(2.0);
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vec2 position = v_textureCoordinates - vec2(0.5);
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float radius = length(position) * lengthScalar;
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float surface = step(radius, u_radiusTS);
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vec4 color = vec4(vec2(1.0), surface + 0.2, surface);
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float glow = 1.0 - smoothstep(0.0, 0.55, radius);
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color.ba += mix(vec2(0.0), vec2(1.0), glow) * 0.75;
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vec4 burst = vec4(0.0);
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// The following loop has been manually unrolled for speed, to
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// avoid sin() and cos().
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//
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//for (float i = 0.4; i < 3.2; i += 1.047) {
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// vec2 direction = vec2(sin(i), cos(i));
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// burst += 0.4 * addBurst(position, direction, lengthScalar);
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//
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// direction = vec2(sin(i - 0.08), cos(i - 0.08));
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// burst += 0.3 * addBurst(position, direction, lengthScalar);
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//}
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burst += 0.4 * addBurst(position, vec2(0.38942, 0.92106), lengthScalar); // angle == 0.4
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burst += 0.4 * addBurst(position, vec2(0.99235, 0.12348), lengthScalar); // angle == 0.4 + 1.047
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burst += 0.4 * addBurst(position, vec2(0.60327, -0.79754), lengthScalar); // angle == 0.4 + 1.047 * 2.0
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burst += 0.3 * addBurst(position, vec2(0.31457, 0.94924), lengthScalar); // angle == 0.4 - 0.08
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burst += 0.3 * addBurst(position, vec2(0.97931, 0.20239), lengthScalar); // angle == 0.4 + 1.047 - 0.08
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burst += 0.3 * addBurst(position, vec2(0.66507, -0.74678), lengthScalar); // angle == 0.4 + 1.047 * 2.0 - 0.08
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// End of manual loop unrolling.
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color += clamp(burst, vec4(0.0), vec4(1.0)) * 0.15;
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gl_FragColor = clamp(color, vec4(0.0), vec4(1.0));
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}
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