// returns frame at ray-intersection point, with normal pointing *outwards*
Frame3 make_hud_sphere_frame(float fHUDRadius, float fHorzAngleDeg, float fVertAngleDeg)
{
Ray r = MathUtil.MakeRayFromSphereCenter(fHorzAngleDeg, fVertAngleDeg);
float fRayT = 0.0f;
MathUtil.IntersectRaySphere(r.origin, r.direction, Vector3.zero, fHUDRadius, out fRayT);
// fRayT is negative inside sphere (?)
Vector3 v = r.origin + Math.Abs(fRayT) * r.direction;
return(new Frame3(v, v.normalized));
}
