raycasting.glsl

// Buffer

const float PI = 3.1415926535897932384626433832795;

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
	vec2 uv = fragCoord.xy / iResolution.xy;
    vec2 mouse = iMouse.xy / iResolution.xy;
    
    float angle = 2.0 * PI * uv.x;
    float radius = uv.y;
    
    bool shadowed = false;
    
    for (int i=0; i<512; i++) {
        float r = 512.0 / float(i);
        vec2 xy = mouse + r * vec2(cos(angle), sin(angle));
        
        vec4 pixel = texture2D(iChannel0, xy);
        if ((pixel.z < 1.0) && (r < radius)) {
        	shadowed = true;
        }
    }
    if (shadowed) {
    	fragColor = vec4(radius, 0.0, 1.0, 1.0);
    } else {
        fragColor = vec4(angle/(2.0*PI), radius, 0.0, 1.0);
    }
}

// Image

const float PI = 3.1415926535897932384626433832795;


void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
	vec2 uv = fragCoord.xy / iResolution.xy;
    vec2 mouse = iMouse.xy / iResolution.xy;
    
    vec2 offset = mouse - uv;
    
    
    float angle = atan(offset.y / offset.x);
    float radius = sqrt(offset.x * offset.x + offset.y*offset.y);
    
    
    fragColor = texture2D(iChannel1, vec2(angle/(2.0 * PI), radius));
    
    
    //fragColor = texture2D(iChannel1, uv);
    //return;
}rn;
}