How to avoid loss of precision when reading large igs/step models

When I use IGESCAFControl_Reader or IGESControl_Reader to load a larger model and display it through AIS_InteractiveContext (or convert it to glb model), the circle of the original model will become a quadrilateral, the curve will become a straight line, I would like to ask if there is a solution to solve the problems?

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Josh Green's picture

Add a supplement, Even if the model is not very large, but there are both large and small circles in the model and the diameter of the big circle is 20 times the diameter of the small circle, the default Deflection is preset according to the big circle, how to bind the preset value of this Deflection to the small circle

gkv311 n's picture

Small circles are tessellated following required linear deflection (IMeshTools_Parameters::Deflection), so you might need to tune this parameter, if quality doesn't look well to you.

Angular deflection (IMeshTools_Parameters::Angle) might help displaying small features in more detail, but there is also a IMeshTools_Parameters::MinSize parameter that you might want to tune as well. MinSize is deduced from linear deflection by default and prevents BRepMesh to generate too small triangles.

Josh Green's picture

thx,firstly it works. The default parameter may be related to the size of the model, it may be sufficient for most mesh displays. but by Changing the Deflection and Angle will make the whole model much larger. dose occ has API for detail (arc) mesh optimization?