Function triangleSolidAngle

source/MRTest/MRDipoleTests.cpp:12–23

see (6) in https://users.cs.utah.edu/~ladislav/jacobson13robust/jacobson13robust.pdf

/// see (6) in https://users.cs.utah.edu/~ladislav/jacobson13robust/jacobson13robust.pdf
static float triangleSolidAngle( const Vector3f & p, const Triangle3f & tri )
{
    Matrix3f m;
    m.x = tri[0] - p;
    m.y = tri[1] - p;
    m.z = tri[2] - p;
    auto x = m.x.length();
    auto y = m.y.length();
    auto z = m.z.length();
    auto den = x * y * z + dot( m.x, m.y ) * z + dot( m.y, m.z ) * x + dot( m.z, m.x ) * y;
    return 2 * std::atan2( m.det(), den );
}

TEST(MRMesh, TriangleSolidAngle)
{