Spatial visibility texture




Texturing, Architecture


Houdini 19.5

1 Description

A texture map indicating hidden areas based on visibility distances. Very vaguely inspired by

2 Code discussion

Rays are casted in all directions with sample_circle_uniform and the intersect-function. If a wall curve has been hit then its tangent is checked against the ray direction normalize(cross(dir, -t)). Whenever the cross products Y component is positive if(m.y > 0.0) the ray is inside the curve, so we can add its distance to the sum which gets divided by the number of samples.

int samples = chi('samples');
float range = chf('range');

float sum = 0.0;
for(int i = 0; i < samples; i++){

    float u = rand(i, i@ix * i@iz);
    vector2 c = sample_circle_edge_uniform(u);
    vector dir = set(c.x, 0.0, c.y);
    vector pos;
    vector uvw;
    int prim = intersect(1, v@P, dir * 10.0, pos, uvw);
    if(prim < 0) continue;
    vector t = primuv(1, 'tangentu', prim, uvw);
    vector m = normalize(cross(dir, -t));
    if(m.y > 0.0){
        float d = distance(pos, v@P);
        sum += d;
f@d = sum / float(samples) / range;