How to improve interactive performance for large STL meshes in OCCT 7.5?

MING FENG HSIEH
Wed, 02/04/2026 - 09:30

Forums:

I am currently using Open CASCADE Technology (OCCT) 7.5 to load a large STL model of approximately 1.9 GB.
After reading the file and displaying it using AIS_Shape, I experience severe performance issues during basic interactions such as model rotation, translation, and bounding box updates.

The viewer often freezes for several seconds even for simple transformations.

I would like to ask whether there are recommended best practices or optimization techniques in OCCT for handling very large STL meshes. In particular:

*Are there performance considerations when using AIS_Shape for large triangulated models?

*Are there preferred approaches such as MeshVS, AIS_Triangulation, or other visualization methods for large STL data?

*Are there recommended ways to manage Bnd_Box updates and transformations efficiently?

Any guidance on improving interactive performance with large mesh-based models would be greatly appreciated.

gkv311 n
Wed, 02/04/2026 - 12:25

What is your current approach to read and display STL file?

STL file doesn't define B-Rep information, so the usual way is to display it as a mesh object in a CAD viewer:

// read STL
Handle(Poly_Triangulation) aTriangles = RWStl::ReadFile("myfile.stl");

// wrap it into a triangulation-only face for visualization
TopoDS_Face aFace;
BRep_Builder().MakeFace(aFace, aTriangles);

// display in the viewer
Handle(AIS_Shape) aPrs = new AIS_Shape(aFace);
theCtx->Display (aPrs, AIS_Shaded, 0, false);
...

MING FENG HSIEH
Thu, 02/05/2026 - 11:15

Thank you for your reply!

I am currently using the approach you mentioned. However, to enable the selection of mesh endpoints, I ended up creating an additional MeshVS_Mesh object. While this works, it has significantly impacted the performance, making the application run much slower due to the overhead of managing multiple mesh representations.

Is there a more efficient way to enable vertex/endpoint selection directly on a single mesh object without duplicating it? I am looking for a solution that maintains high performance while allowing me to switch between object-level and vertex-level selection.

gkv311 n
Thu, 02/05/2026 - 16:31

However, to enable the selection of mesh endpoints, I ended up creating an additional MeshVS_Mesh object.

MeshVS is a legacy component implementing display and selection facilities using mostly 'old-style' approaches; so that in the current state it doesn't scale well for large meshes.

What you are probably looking for is an approach used by AIS_PointCloud, which relies on Select3D_SensitivePrimitiveArray to pick points with much smaller overhead than MeshVS (in memory and in performance).

There is no similar class for triangulation yet. AIS_Triangulation doesn't implement selection at all, but you may use AIS_Triangulation::Compute() implementation as a code snippet for filling in Graphic3d_ArrayOfTriangles from Poly_Triangulation. Then you may passGraphic3d_ArrayOfTriangles to Select3D_SensitivePrimitiveArray::InitPoints() as AIS_PointCloud::ComputeSelection::() does or as Select3D_SensitivePrimitiveArray::InitTriangulation() to be able select triangles in addition to nodes.

Though you will have to dig a little bit further to understand the basic logic of AIS for visualization and selection (take also look to AIS tutorials).