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is there a more elegant way to compute the Matrix4D between two vectors - i.e. Normal and WCS

  • 1.  is there a more elegant way to compute the Matrix4D between two vectors - i.e. Normal and WCS

    Posted 25 days ago
    Edited by Ronny Schneider 24 days ago

    Currently I'm doing it the following way, result is correct, just wondering if there is a one-liner for it.

                                centerp = o.OriginOfUcs
                            nv = o.Normal.Clone()
                            # will only work if Normal != 0, 0, 1
                            vx = nv.Clone()
                            # rotate 90 degrees around world-Z axis and make it level with world horizon
                            vx.RotateAboutZ(math.pi/2)
                            vx.Horizon = 0
                            # don't really need vy here - do it anyway
                            # clone the axis and rotate it 90 degrees around Normal
                            vy = vx.Clone()
                            vy.Rotate(BiVector3D(nv, math.pi/2))
                            # vx, vy and Normal are now square to each other
                            
                            # compute matrix to line up UCS-X,Z with World-X,Z axis
                            rottozero = Spinor3D.ComputeRotation(vx, nv, Vector3D(1,0,0), Vector3D(0,0,1))
                            # transformation to 0, 0, 0
                            #matrixtozero = Matrix4D.BuildTransformMatrix(Vector3D(centerp), Vector3D(centerp, Point3D(0, 0, 0)), rottozero, Vector3D(1,1,1))
                            #matrixbackfromzero = Matrix4D.Inverse(matrixtozero)
                            # transformation without shift - just flatten it
                            matrixtoflat = Matrix4D.BuildTransformMatrix(Vector3D(centerp), Vector3D(0, 0, 0), rottozero, Vector3D(1,1,1))
                            matrixbackfromflat = Matrix4D.Inverse(matrixtoflat)

    Is there a built-in function to compute the Matrix4D between a Normal vector and World? Edit: between UCS-Normal and World-Z, but keeping UCS-Origin

    I've tried,

    Plane3D.GetTransformMatrix(o.Normal)

    as shown in the ConvertToLinestring sample macro, but the result is wrong.



    ------------------------------
    Ronny Schneider
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  • 2.  RE: is there a more elegant way to compute the Matrix4D between two vectors - i.e. Normal and WCS

    Posted 25 days ago

    I'm guessing you tried the Matrix constructor (point, vector, vector)?
    In this case, I believe the Z would be the Normal and Point3D.Zero as the origin. 




    ------------------------------
    Bryce Haire
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    Original Message


  • 3.  RE: is there a more elegant way to compute the Matrix4D between two vectors - i.e. Normal and WCS

    Posted 24 days ago

    Hello Bryce,

    I probably did back then. Just reusing old code right now.

    The one you suggested gets it almost right, but the rotation about Z is wrong.

    May have something to do with me trying to rotate on the spot, and not world 0,0,0.

    In this specific use case, I don't want the Matrix from UCS to World (with 0,0,0), but between UCS-Normal and World-Z and keep UCS-Origin.

    I'll keep playing around with it. I've got a version that does exactly what I want, just trying to simplify it.



    ------------------------------
    Ronny Schneider
    ------------------------------

    Original Message