/**
* @param vRayStart Start point of an infinite ray.
* @param vRayOffset Direction of the ray, parametric t multiplier.
* @param fT0 Filled in with time of first intersection (if present).
* @param fT1 Filled in with time of second intersection (if present).
* @return The number of intersections found.
*/
UINT32 CCircle::GetLineIntersectionTimes(CFVec2Arg vRayStart, CFVec2Arg vRayOffset, GDE::FLOAT32 &fT0, GDE::FLOAT32 &fT1) const
{
const CFVec2 vToRay = vRayStart - m_vCentre;
// TODO: reformulate without the square root?
const FLOAT32 fExtentsRecip = 1.0f/vRayOffset.Magnitude();
const FLOAT32 fRayDotToRay = vToRay.DotProduct( vRayOffset ) * fExtentsRecip;
const FLOAT32 fDiscr = fRayDotToRay*fRayDotToRay - (vToRay.SquareMagnitude()-m_fRadius*m_fRadius);
if ( fDiscr < 0.0f )
{
return 0; // no intersections.
}
if ( fDiscr == 0.0f )
{
fT0 = -fRayDotToRay * fExtentsRecip;
return 1; // one intersection, just touching
} else
{
const FLOAT32 fRoot = sqrtf( fDiscr );
fT0 = (-fRayDotToRay - fRoot) * fExtentsRecip;
fT1 = (-fRayDotToRay + fRoot) * fExtentsRecip;
return 2; // two intersections.
}
}
