c++ - Eigen how to find all coplanar faces from triangle mesh normals without looping

Question

I have a mesh which is mostly planar I'd like to find all the coplanar faces by using normals. I'll take that by finding all normals pointing in the same direction; that is, checking all collinear normal vectors within a tolerance, by a dot product. But that means I've to check by looping for every vector.

MatrixXd VL = ... // Collinear vectors list taken from mesh normals
collinearEpsilon = 1e-8;

for (long i = 0, j = 0; i < VL.rows(); i++)
{
    // get previous vector
    Vector3d p = VL.row(i);

    // loop around last vector
    j = i + 1;
    if (j == size)
    {
        j = 0;
    }

    // get next vector
    Vector3d n = VL.row(j);

    // if dot product is one, they're colinear
    VectorXd CL(1);
    p = p.normalized();
    n = n.normalized();
    CL(0) = 1 - abs(p.dot(n));

    // check with epsilon
    if (CL.isZero(collinearEpsilon))
        // vector is collinear
    else
        // exit on first non-collinear
}

Thus my question: is there a better way to check the collinearity of a set of vectors, all together in a more compact way without looping, in Eigen?

EDIT: added assuming mesh is mostly planar

question from:https://stackoverflow.com/questions/65884682/eigen-how-to-find-all-coplanar-faces-from-triangle-mesh-normals-without-looping

Answer 1

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