You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
67 lines
1.8 KiB
GLSL
67 lines
1.8 KiB
GLSL
// Author @patriciogv - 2015
|
|
// http://patriciogonzalezvivo.com
|
|
|
|
#ifdef GL_OES_standard_derivatives
|
|
#extension GL_OES_standard_derivatives : enable
|
|
#endif
|
|
|
|
#ifdef GL_ES
|
|
precision mediump float;
|
|
#endif
|
|
|
|
#define PI 3.14159265359
|
|
#define TWO_PI 6.28318530718
|
|
|
|
uniform vec2 u_resolution;
|
|
uniform vec2 u_mouse;
|
|
uniform float u_time;
|
|
|
|
// Antialiazed Step function
|
|
// from http://webstaff.itn.liu.se/~stegu/webglshadertutorial/shadertutorial.html
|
|
float aastep(float threshold, float value) {
|
|
#ifdef GL_OES_standard_derivatives
|
|
float afwidth = 0.7 * length(vec2(dFdx(value), dFdy(value)));
|
|
return smoothstep(threshold-afwidth, threshold+afwidth, value);
|
|
#else
|
|
return step(threshold, value);
|
|
#endif
|
|
}
|
|
|
|
// get distance field of a polygon in the center
|
|
// where N is the number of sides of it
|
|
// ================================
|
|
float shapeDF (vec2 st, int N) {
|
|
st = st *2.-1.;
|
|
float a = atan(st.x,st.y)+PI;
|
|
float r = TWO_PI/float(N);
|
|
return cos(floor(.5+a/r)*r-a)*length(st);
|
|
}
|
|
|
|
// draw a polygon in the center
|
|
// where N is the number of sides of it
|
|
// ================================
|
|
float shape (vec2 st, int N, float width) {
|
|
return 1.0-aastep(width,shapeDF(st,N));
|
|
}
|
|
|
|
// draw the border of a polygon in the center
|
|
// where N is the number of sides of it
|
|
// ================================
|
|
float shapeBorder (vec2 st, int N, float size, float width) {
|
|
return shape(st,N,size)-shape(st,N,size-width);
|
|
}
|
|
|
|
void main(){
|
|
vec2 st = gl_FragCoord.xy/u_resolution.xy;
|
|
st.x *= u_resolution.x/u_resolution.y;
|
|
vec3 color = vec3(0.0);
|
|
color.r += shapeBorder(st, 3, .1, .06);
|
|
|
|
vec2 offset = vec2(.0,-.1);
|
|
color += shapeBorder(st+offset+vec2(.045,.125), 3, .05, .03);
|
|
color += shapeBorder(st+offset+vec2(-.045,.125), 3, .05, .03);
|
|
color += shapeBorder(st+offset+vec2(0.,0.05), 3, .05, .03);
|
|
|
|
gl_FragColor = vec4(color,1.0);
|
|
}
|