ray_marching.glsl

// uniform vec3 iResolution;// viewport resolution (in pixels)
// uniform float iTime;// shader playback time (in seconds)
// uniform float iTimeDelta;// render time (in seconds)
// uniform int iFrame;// shader playback frame
// uniform float iChannelTime[4];// channel playback time (in seconds)
// uniform vec3 iChannelResolution[4];// channel resolution (in pixels)
// uniform vec4 iMouse;// mouse pixel coords. xy: current (if MLB down), zw: click
// uniform samplerXX iChannel0..3;// input channel. XX = 2D/Cube
// uniform vec4 iDate;// (year, month, day, time in seconds)
// uniform float iSampleRate;// sound sample rate (i.e., 44100)

float dfield(vec3 p) {
    vec3 s1 = vec3(0, 0, 5);

    float d = distance(p, s1) - 1.0;
    return d;
}


vec4 march(vec3 ray) {
    vec3 color = vec3(0, 0, 0);
    float d = 0.;
    float delta = 0.;
    for(int s = 0; s < 128; s++) {
        delta = dfield(ray * d);
        if(delta > 0.01) {
            d += delta;
        } else {
            // return vec4(ray*d, 1);
            vec3 n = normalize(ray * d - vec3(0,0,5));
            float nol = dot(n, normalize(vec3(sin(iTime), 1, -1)));
            color += vec3(nol);
            break;
        }
    }
    return vec4(color, 1);
}

void main() {
    vec2 uv = (gl_FragCoord.xy-.5 * iResolution.xy) / iResolution.y;
    vec3 ray = vec3(0, 0, -1);
    ray = normalize(vec3(uv, 0) - ray);
    gl_FragColor = vec4(ray, 1);
    gl_FragColor = march(ray);
}