int IntersectRaySphereX( const SphereX& sphere,
const Vector3X& p,
const Vector3X& dir,
Fixed* t )
{
Vector3X raySphere = sphere.origin - p;
Fixed raySphereLen2 = DotProduct( raySphere, raySphere );
Fixed sphereR2 = sphere.radius*sphere.radius;
if (raySphereLen2 < sphereR2)
{
// Origin is inside the sphere.
return grinliz::INSIDE;
}
else
{
// Clever idea: what is the rays closest approach to the sphere?
// see: http://www.devmaster.net/wiki/Ray-sphere_intersection
Fixed closest = DotProduct(raySphere, dir);
if (closest < 0) {
// Then we are pointing away from the sphere (and we know we aren't inside.)
return grinliz::REJECT;
}
Fixed halfCordLen = (sphereR2 - raySphereLen2) / DotProduct(dir, dir) + (closest*closest);
if ( halfCordLen > 0 ) {
*t = closest - halfCordLen.Sqrt();
return grinliz::INTERSECT;
}
}
return grinliz::REJECT;
}
