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parabola.frag
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parabola.frag
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// Author: Inigo Quiles
// Title: Parabola
#ifdef GL_ES
precision mediump float;
#endif
uniform vec2 u_resolution;
uniform float u_time;
// Function from Iñigo Quiles
// www.iquilezles.org/www/articles/functions/functions.htm
float parabola( float x, float k ){
return pow( 4.0*x*(1.0-x), k );
}
float plot(vec2 st, float pct){
return smoothstep( pct-0.02, pct, st.y) -
smoothstep( pct, pct+0.02, st.y);
}
void main() {
vec2 st = gl_FragCoord.xy/u_resolution;
float y = parabola(st.x,1.0);
vec3 color = vec3(y);
float pct = plot(st,y);
color = (1.0-pct)*color+pct*vec3(0.0,1.0,0.0);
gl_FragColor = vec4(color,1.0);
}