Project VectDg onto a surface to get a 2D vector

[Jim Herron]

Hello,

I have a vector in 3D space (VectDg) and I want to project it onto a IUVSurface_DG/IBRepFace_DG at a certain position. I can do this using VectDg n = IUVSurface_DG.GetNormal() and then use myVector.MakeOrtho(n).
Then I can use

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dirU = GetTangent(uv, true); dirV = GetTangent(uv, false);

Then du = myVector.Product(dirU) and dv = myVector.Product(dirV) will be the 2D coordinates of the projection in uv space.
Is there a simpler way?

Thank you for your answers,
Herron

[Eric Rayner]

This should work. After the myVector.MakeOrtho(n) you vector will be tangential to the surface.

A little shorter way:

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IFrame_DG frame = IUVSurface_DG.GetUVAlignedFrame(uv);
VectDg vectTangential = frame.ToLocal(myVector);

vectTangential[0] and vectTangential[1] will be the coordinates in the parameters space.