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Inquire Bspline Surface Normal Direction

Level 7

Inquire Bspline Surface Normal Direction

I am writing lisp code to thicken a bspline surface. However, I need to determine the surface normal direction to know which direction this surface will be thickened. What command returns the face normal direction of a bspline surface?

Thank you.

Scott

3 REPLIES 3

Re: Inquire Bspline Surface Normal Direction

I assume that you want to write code to thicken a bspline surface because you don't have a license for the Surfacing module, because that module has a Thicken command.

Since a Bspline face is generally "curvey", there is no single normal direction for it. The normal direction will, in general, vary across the surface. The command sd-inq-face-pnt can be used to determine the normal at a point on the surface. You can use sd-get-pnt-on-face to find a point on the face, although you will probably need to use sd-proj-pnt-on-face (along with sd-face-relax-pnt)to convert that point into something that can be used for sd-inq-face-pnt.

Re: Inquire Bspline Surface Normal Direction

The command Thicken is available since 18.0 without surfacing module

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Re: Inquire Bspline Surface Normal Direction

Thank you for your response. I was able to use sd-inq-face-point to find the normal direction of the bspline surface which I was then able to use to determine which direction to thicken.