<OPENGL 12> WEB GLSL

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
const float e = 1e-8;

struct Shape{
    float sdf;
    vec3 color;
};

Shape combine_sdf(Shape a, Shape b){
    Shape temp;
    temp.sdf = min(a.sdf,b.sdf);
    temp.color = a.color * float(a.sdf<=0.0) +  b.color * float(b.sdf<=0.0) ;
    return temp;
}

float circle_sdf (vec2 pos,vec2 center,float radius)
{
    return length(pos-center) - radius;
}


void main()
{
    float radius = 0.2;
    vec2 pos = gl_FragCoord.xy / u_resolution - vec2(0.5,0.5);
    Shape cle01= Shape(circle_sdf(pos,vec2(-0.1, 0.0), radius), vec3(1,0,0));
    Shape cle02= Shape(circle_sdf(pos,vec2(0.1,  0.0), radius), vec3(0,0,1));
    Shape scene = combine_sdf(cle01,cle02);
    vec3 color = float(scene.sdf <=0.0) * scene.color;
    gl_FragColor = vec4(color, 1.0);
    
}