1.并集

float Circle(vec2 uv,vec2 center,float radius)
{
    float d = length(uv - center);
    return step(d,radius);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord/iResolution.xy;
    uv -= 0.5;

    //将uv的x坐标进行放大
    uv.x *= iResolution.x / iResolution.y;

    float c = Circle(uv,vec2(-0.3,-0.2),0.1);
    float d = Circle(uv,vec2(0.2,0),0.2);
    c = c + d;
    fragColor = vec4(vec3(c),1.0);
}

效果:

2.差集

float Circle(vec2 uv,vec2 center,float radius)
{
    float d = length(uv - center);
    return step(d,radius);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord/iResolution.xy;
    uv -= 0.5;

    //将uv的x坐标进行放大
    uv.x *= iResolution.x / iResolution.y;

    float c = Circle(uv,vec2(0.2,-0.2),0.1);
    float d = Circle(uv,vec2(0.2,0),0.2);
    c = d - c;
    fragColor = vec4(vec3(c),1.0);
}

效果:

3.交集

float Circle(vec2 uv,vec2 center,float radius)
{
    float d = length(uv - center);
    return step(d,radius);
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = fragCoord/iResolution.xy;
    uv -= 0.5;

    //将uv的x坐标进行放大
    uv.x *= iResolution.x / iResolution.y;

    float c = Circle(uv,vec2(0.2,-0.2),0.1);
    float d = Circle(uv,vec2(0.2,0),0.2);
    c = d * c;
    fragColor = vec4(vec3(c),1.0);
}

效果: