qreal QGLBezierPatch::intersection
(qreal result, int depth, const QRay3D& ray, bool anyIntersection,
qreal xtex, qreal ytex, qreal wtex, qreal htex, QVector2D *tc)
{
// Check the convex hull of the patch for an intersection.
// If no intersection with the convex hull, then there is
// no point subdividing this patch further.
QBox3D box;
for (int point = 0; point < 16; ++point)
box.unite(points[point]);
if (!box.intersects(ray))
return result;
// Are we at the lowest point of subdivision yet?
if (depth <= 1) {
// Divide the patch into two triangles and intersect with those.
QTriangle3D triangle1(points[0], points[3], points[12]);
qreal t = triangle1.intersection(ray);
if (!qIsNaN(t)) {
result = combineResults(result, t);
if (result == t) {
QVector2D uv = triangle1.uv(ray.point(t));
QVector2D tp(xtex, ytex);
QVector2D tq(xtex + wtex, ytex);
QVector2D tr(xtex, ytex + htex);
*tc = uv.x() * tp + uv.y() * tq + (1 - uv.x() - uv.y()) * tr;
}
} else {
QTriangle3D triangle2(points[3], points[15], points[12]);
qreal t = triangle2.intersection(ray);
if (!qIsNaN(t)) {
result = combineResults(result, t);
if (result == t) {
QVector2D uv = triangle2.uv(ray.point(t));
QVector2D tp(xtex + wtex, ytex);
QVector2D tq(xtex + wtex, ytex + htex);
QVector2D tr(xtex, ytex + htex);
*tc = uv.x() * tp + uv.y() * tq + (1 - uv.x() - uv.y()) * tr;
}
}
}
} else {
// Subdivide the patch to find the point of intersection.
QGLBezierPatch patch1, patch2, patch3, patch4;
subDivide(patch1, patch2, patch3, patch4);
--depth;
qreal hwtex = wtex / 2.0f;
qreal hhtex = htex / 2.0f;
result = patch1.intersection
(result, depth, ray, anyIntersection,
xtex, ytex, hwtex, hhtex, tc);
if (anyIntersection && !qIsNaN(result))
return result;
result = patch2.intersection
(result, depth, ray, anyIntersection,
xtex + hwtex, ytex, hwtex, hhtex, tc);
if (anyIntersection && !qIsNaN(result))
return result;
result = patch3.intersection
(result, depth, ray, anyIntersection,
xtex, ytex + hhtex, hwtex, hhtex, tc);
if (anyIntersection && !qIsNaN(result))
return result;
result = patch4.intersection
(result, depth, ray, anyIntersection,
xtex + hwtex, ytex + hhtex, hwtex, hhtex, tc);
}
return result;
}