# .step import source code questions **URL:** \ **Category:** General Questions\ **Created:** [March 4, 2026, 2:49pm UTC](https://prepomax.discourse.group/t/step-import-source-code-questions/3312 "2026-03-04T14:49:35Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![alxgrn](https://avatars.discourse-cdn.com/v4/letter/a/a5b964/32.png) [@alxgrn](https://prepomax.discourse.group/u/alxgrn)\ **Post date:** [March 4, 2026, 2:49pm UTC](https://prepomax.discourse.group/t/step-import-source-code-questions/3312/1 "2026-03-04T14:49:35Z")
Looking at the source code I’m quiet confused as to how the program manages to import .stp and .iges in c#. Is it using opencascade? The ActiViz OpenSource Edition uses an older version of vtk which does not have the .step import native. Thank you ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [March 4, 2026, 4:31pm UTC](https://prepomax.discourse.group/t/step-import-source-code-questions/3312/2 "2026-03-04T16:31:47Z")
> [@alxgrn](#): > > Is it using opencascade? Yes, PrePoMax uses OpenCascade like FreeCAD. And maybe Netgen for some CAD geometry handling operations too. ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [March 4, 2026, 5:09pm UTC](https://prepomax.discourse.group/t/step-import-source-code-questions/3312/3 "2026-03-04T17:09:59Z")
PrePoMax does not have a geometry kernel. It uses OpenCascade through Netgen. The netgen is used to read the step file and export its triangulation and edges, along with node, edge, and surface IDs. This is saved in a txt file that PrePoMax reads and displays. So the geometry is not really in PrePoMax (C#), it is in Netgen (C++).