AutoLisp source code for the intersection of 2 3DFACE and contour lines

It is an AutoLisp function for the intersection of 2 triangular 3DFACE entities.
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://rcad.eu/autolisp_source/