// intersect lines with plane
void Slicer::CalcCuttingPlane(float where, CuttingPlane &plane, const Matrix4f &T)
{
#if CUTTING_PLANE_DEBUG
cout << "intersect with z " << where << "\n";
#endif
plane.Clear();
plane.SetZ(where);
Vector3f min = T*Min;
Vector3f max = T*Max;
plane.Min.x = min.x;
plane.Min.y = min.y;
plane.Max.x = max.x;
plane.Max.y = max.y;
Vector2f lineStart;
Vector2f lineEnd;
bool foundOne = false;
int num_cutpoints;
for (size_t i = 0; i < triangles.size(); i++)
{
foundOne=false;
CuttingPlane::Segment line(-1,-1);
num_cutpoints = triangles[i].CutWithPlane(where, T, lineStart, lineEnd);
if (num_cutpoints>0)
line.start = plane.RegisterPoint(lineStart);
if (num_cutpoints>1)
line.end = plane.RegisterPoint(lineEnd);
// Check segment normal against triangle normal. Flip segment, as needed.
if (line.start != -1 && line.end != -1 && line.end != line.start)
// if we found a intersecting triangle
{
Vector3f Norm = triangles[i].Normal;
Vector2f triangleNormal = Vector2f(Norm.x, Norm.y);
Vector2f segmentNormal = (lineEnd - lineStart).normal();
triangleNormal.normalise();
segmentNormal.normalise();
if( (triangleNormal-segmentNormal).lengthSquared() > 0.2f)
// if normals does not align, flip the segment
line.Swap();
plane.AddLine(line);
}
}
}
