Geometry::HitResult<double> Section::
intersectRay(const Geometry::Ray<double,3>& ray) const
{
/* based on "Fast, Minimum Storage Ray/Triangle Intersection" by Tomas
Moeller and Ben Trumbore */
Geometry::Vector<double,3> rayOrig(ray.getOrigin()[0],ray.getOrigin()[1],ray.getOrigin()[2]);
const Geometry::Vector<double,3>& rayDir = ray.getDirection();
/* begin calculating determinant - also used to calculate U parameter */
Geometry::Vector<double,3> pvec = Geometry::cross(rayDir, end);
/* if determinant is near zero, ray lies in plane of triangle */
Scalar det = start * pvec;
if (det>-EPSILON && det<EPSILON)
return Geometry::HitResult<double>();
Scalar invDet = Scalar(1) / det;
/* calculate U parameter and test bounds */
Scalar u = (rayOrig*pvec) * invDet;
if (u < Scalar(0))
return Geometry::HitResult<double>();
/* prepare to test V parameter */
Geometry::Vector<double,3> qvec = Geometry::cross(rayOrig, start);
/* calculate V parameter and test bounds */
Scalar v = (rayDir*qvec) * invDet;
if (v < Scalar(0))
return Geometry::HitResult<double>();
/* calculate t, ray intersects triangle */
Scalar t = (end*qvec) * invDet;
return Geometry::HitResult<double>(t);
}
Geometry::HitResult<double> Section::
intersectPlane(const Geometry::Ray<double,3>& ray, bool cullBackFace) const
{
Geometry::Vector<double,3> rayOrig(ray.getOrigin()[0],ray.getOrigin()[1],ray.getOrigin()[2]);
const Geometry::Vector<double,3>& rayDir = ray.getDirection();
/* the ray intersects the plane at poing t for which (ray(t)-PlaneOrigin) is
orthogonal to the normal. See http://softsurfer.com/Archive/algorithm_0104/algorithm_0104B.htm#Line-Plane Intersection
for nice description */
double nDotDir = normal * rayDir;
//exit on back-facing planes if so desired
if (cullBackFace && nDotDir>0.0)
return Geometry::HitResult<double>();
//handle the parallel case
if (nDotDir>-EPSILON && nDotDir<EPSILON)
{
Geometry::Vector<double,3> toOrig = rayOrig - start;
double nDotToOrig = normal * toOrig;
//coincident
if (nDotToOrig>-EPSILON && nDotToOrig<EPSILON)
return Geometry::HitResult<double>(0.0);
//disjoint
else
return Geometry::HitResult<double>();
}
//compute the intersection parameter
return Geometry::HitResult<double>((normal * (start - rayOrig)) / nDotDir);
}