karma_procedurals/sphere_intersect.vfl

/*%vcc -l intersect.otl -O vop % */

#include "math.h"

cvex
main(
    // Inputs
    vector ray_org = 0; // ray origin given by procedural
    vector ray_dir = 0; // ray direction given by procedural
    // Parameters
    float  radius  = 1;
    vector color   = {1, 1, 1};
    // Outputs
    export float   distance = 0; // distance to hit
    export vector  Ng       = 0; // normal at hit
    export vector  uvw      = 0; // uvw
    export int     hit      = 0; // boolean determining whether there was a hit
    )
{
    // intersect with sphere
    hit = 0;
    float b = 2*dot(ray_org, ray_dir);
    float c = length2(ray_org) - radius*radius;
    float d = b*b - 4.0f*c;
    // check discriminant for hit
    if (d > 0)
    {
        d = sqrt(d);
        float dist0 = 0.5f * (-b - d);
        float dist1 = 0.5f * (-b + d);
        if (dist0 > 0 && dist0 < dist1)
        {
            hit = 1;
            distance = dist0;
        }
        else if (dist1 > 0)
        {
            hit = 1;
            distance = dist1;
        }
        Ng = ray_org + distance * ray_dir;
        Ng = normalize(Ng);
        uvw.x = fit(atan2(Ng.x, Ng.z), -PI, PI, 0, 1);
        uvw.y = fit(asin(Ng.y), -PI_2, PI_2, 0, 1);
        uvw.z = 0;
    }
}