public HitRecord Hit(Ray3 r, double tMin, double tMax)
{
Vector3 oc = r.Origin - this.center;
double a = r.Direction.Dot(r.Direction);
double b = 2.0 * oc.Dot(r.Direction);
double c = oc.Dot(oc) - this.radius * this.radius;
double discriminant = b * b - 4 * a * c;
if (discriminant > 0)
{
double temp = (-b - System.Math.Sqrt(discriminant)) / (2.0 * a);
if (temp < tMax && temp > tMin)
{
Vector3 p = r.PointAtParameter(temp);
HitRecord record = new HitRecord(
temp,
p,
(p - this.center) / this.radius,
material);
return(record);
}
temp = (-b + System.Math.Sqrt(discriminant)) / (2.0 * a);
if (temp < tMax && temp > tMin)
{
Vector3 p = r.PointAtParameter(temp);
HitRecord record = new HitRecord(
temp,
p,
(p - this.center) / this.radius,
material);
return(record);
}
}
return(null);
}