Intersect 2 3DFACE and contour lines AutoLisp source

It is an AutoLisp function for the intersection of 2 triangular 3DFACE entities.

Function call (setq ls (sitt p1 p2 p3 p4 p5 p6))

-p1 p2 p3, p4, p5, p6 are points of the triangles

-ls is the list of 2 points that define the intersection segment inside the triangles.

You also have 2 test programs that use the intersection function. With one program you can select and intersect 2 3DFACEs, and with the other you can generate the contour lines with a constant step, on the 3DFACE entities in the current DWG.

Can be used in AutoCAD or programs based on IntelliCAD (such as BricsCAD, ProgeCAD, ActCAD, ZWCAD, etc.).

https://youtu.be/vRV3ucUoXcA

You are licensed to use this "Intersect 2 3DFACE AutoLisp source", for drawing or to include it in your programs that you sell.