Lucas de Vries
93 lines
2.6 KiB
Plaintext
93 lines
2.6 KiB
Plaintext
uniform sampler2D texture;
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uniform float time;
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varying vec2 uv;
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//Percent from the center to the edge where the dust should stop
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const float innerRad = 0.05;
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const float outerFade = 0.8;
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//How many different speeds the dust should move at
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const float steps = 36.0;
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//How fast it spins overall
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const float dustSpeed = 0.008;
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//Rate of speed increase, should be an integer
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const float dustSpeedCurve = 3.0;
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//Fixed curve in the dust, should be an integer
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const float fixedSpiral = 3.0;
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//Texture mapping settings to avoid peroidic patterns
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const float texRepeat = 6.0;
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const float stepOffset = 0.2;
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//Temperature stepping as dust approaches the horizon
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const float kPerStep = 0.25;
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const float tempCurve = 3.35;
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//Temp above which the light is artificially brightened
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const float hotTemp = 13000.0;
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//Temp below which the light is artificially darkened
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const float coolTemp = 2200.0;
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const float twopi = 6.28318530718;
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float mixRange(float x, float low, float hi) {
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return clamp((x - low) / (hi - low), 0.0, 1.0);
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}
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vec3 blackBody(float temp) {
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vec3 c;
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c.r = mix(1.0, 0.6234, mixRange(temp, 6400.0, 29800.0));
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c.b = mix(0.0, 1.0, mixRange(temp, 2800.0, 7600.0));
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if(temp < 6600.0)
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c.g = mix(0.22, 0.976, mixRange(temp, 1000.0, 6600.0));
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else
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c.g = mix(0.976, 0.75, mixRange(temp, 6600.0, 29800.0));
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if(temp < coolTemp)
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c *= temp / coolTemp;
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else if(temp > hotTemp)
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c *= (temp / hotTemp);
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return c;
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}
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//Blends a number of rotating sections together
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//Sections rotate at integer multiples of the slowest speed to avoid animation hitching
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void main() {
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vec2 p = (uv - vec2(0.5)) * 2.0;
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float d = length(p);
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if(d > 1.0 || d <= innerRad)
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discard;
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d = 1.0 - ((d - innerRad) / (1.0 - innerRad));
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float a = atan(p.y,p.x);
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//Whatever curve the second smoothstep makes, it works
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gl_FragColor.a = smoothstep(0.0,outerFade,d) * smoothstep(d,1.0,0.995);
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float step = d * steps + 0.5;
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float lowStep = floor(step);
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float hiStep = ceil(step);
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float lowPct = (hiStep - step);
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float hiPct = 1.0 - lowPct;
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vec3 col = vec3(0.0);
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vec3 bbCol = blackBody(kPerStep * pow(step, tempCurve));
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{
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vec2 st = vec2((a / twopi) - time * pow(lowStep, dustSpeedCurve) * dustSpeed + lowStep * stepOffset, (d - time * 4.0) * texRepeat);
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st.y -= fixedSpiral * (a/twopi);
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col += bbCol * (texture2D(texture, st).r * lowPct);
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}
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{
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vec2 st = vec2((a / twopi) - time * pow(hiStep, dustSpeedCurve) * dustSpeed + hiStep * stepOffset, (d - time * 4.0) * texRepeat);
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st.y -= fixedSpiral * (a/twopi);
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col += bbCol * (texture2D(texture, st).r * hiPct);
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}
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gl_FragColor.rgb = col;
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}
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