Apply homogeneous transformation matrix to meshes

[Maia R.]

Dear community,

I need help to apply an homogeneous transformation matrix to meshes. 

I tried to get the rotation (Euler angles) and the translation matrices and apply a composed transformation to the mesh but I failed to obtain a good result as with CloudCompare for example.

Does someone already work with the same problem ?

Thank you,

Best regards

Maia

[Marcel Luethi]

Hi Maia

You cannot directly use a matrix to transform a mesh, as Scalismo works on a higher level of abstraction. But you can easily construct a transformation from a matrix like this::

def homogeneousTransform(matrix4x4 : DenseMatrix[Double]) : Transformation[_3D] = {
  Transformation{
    (point : Point[_3D]) => {
      val pointInHomogeneousCoords = DenseVector(point.x, point.y, point.z, 1.0)
      val transformedPointHomogeneousCoords = matrix4x4 * pointInHomogeneousCoords
      Point3D(transformedPointHomogeneousCoords(0), transformedPointHomogeneousCoords(1), transformedPointHomogeneousCoords(2))
    }
  }
}

val mat : DenseMatrix[Double] = ??? // 4x4 matrix with transformation
val transformation = homogeneousTransform(mat)
val mesh : TriangleMesh[_3D] = ???
val transformedMesh = mesh.transform(transformation)

The more direct would be to specify a transformation directly, using the known rotation (Euler angles) and translation parameters:

val t = RotationAfterTranslation3D(translation = Translation(EuclideanVector3D(1, 1, 1)),
                                   rotation = Rotation(0, 0, 0, center = Point3D(0, 0, 0)))

Best regards,

Marcel

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[V R]

Thank you very much.