//I've come up with something like this (for the 3D case), very raw, educational purposes
float ditance2segment(Vector3D p, Vector3D p0, Vector3D p1){
Vector3D v = p1 - p0;
Vector3D w = p - p0;
float c1 = v.Dot(w);
if (c1 <= 0)
return (p - p1).Length();
float c2 = v.Dot(v);
if (c2 <= c1)
return (p - p1).Length();
float b = c1/c2;
Vector3D pb = p0 + b*v;
return (p - pb).Length();
}
void CrossFieldInterpolation(List<Vector3D>& Contour, List<Vector3D>& ContourN, Vector3D p, Vector3D& crossU, Vector3D& crossV){
int N = Contour.Amount();
for (int i=0; i < N; i++){
Vector3D u = Contour[(i + 1) % N] - Contour[i];
Vector3D n = 0.5*(ContourN[(i + 1) % N] + ContourN[i]);
Vector3D v = -Vector3D::Cross(u,n); //perpendicular vector
u = Vector3D::Normalize(u);
n = Vector3D::Normalize(n);
v = Vector3D::Normalize(v);
float dist = ditance2segment(p, Contour[i], Contour[(i+1)%N]);
crossU += u/(1+dist); //to avoid infinity at points over the segment
crossV += v/(1+dist);
}
crossU = Vector3D::Normalize(crossU);
crossV = Vector3D::Normalize(crossV);
}
不,這是錯誤的...請有人可以幫忙嗎? –