mirror of
https://github.com/patriciogonzalezvivo/thebookofshaders
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46 lines
1.1 KiB
GLSL
46 lines
1.1 KiB
GLSL
// Author @patriciogv - 2015
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// http://patriciogonzalezvivo.com
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#ifdef GL_OES_standard_derivatives
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#extension GL_OES_standard_derivatives : enable
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#endif
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#ifdef GL_ES
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precision mediump float;
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#endif
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#define PI 3.14159265359
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#define TWO_PI 6.28318530718
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uniform vec2 u_resolution;
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uniform vec2 u_mouse;
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uniform float u_time;
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float shape(vec2 st, int N){
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st = st *2.-1.;
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float a = atan(st.x,st.y)+PI;
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float r = TWO_PI/float(N);
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return cos(floor(.5+a/r)*r-a)*length(st);
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}
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// Antialiazed Step function
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// from http://webstaff.itn.liu.se/~stegu/webglshadertutorial/shadertutorial.html
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float aastep(float threshold, float value) {
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#ifdef GL_OES_standard_derivatives
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float afwidth = 0.7 * length(vec2(dFdx(value), dFdy(value)));
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return smoothstep(threshold-afwidth, threshold+afwidth, value);
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#else
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return step(threshold, value);
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#endif
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}
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void main(){
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vec2 st = gl_FragCoord.xy/u_resolution.xy;
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st.x *= u_resolution.x/u_resolution.y;
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vec3 color = vec3(0.0);
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float d = 0.0;
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d = min(shape(st,3),shape(st+vec2(0.,0.19),4));
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gl_FragColor = vec4(vec3(1.0-aastep(.2,d)),1.0);
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} |