Can we inspect the surface being merged by two faces in OpenCASCADE?


I tried to road a IGES model in my application,but I found a surface in which the direction of sample point is different.(as picture)

I think the surface maybe be merged by two faces.
Someone know how to inspect the surface whether being merged by two faces or not?

Forum supervisor's picture

Hello Dante,

Could you please explain what exactly you mean by "the direction of sample point"?
Do you mean the normal direction at points, or you mean direction between two neighbor points, or anything else?

Thanks in advance,
Forum supervisor

Dante Liu's picture

the direction of sample point is similar to direction between two neighbor points. I used a parametric formula (U = t * a + b) to sample point in the parametric patch of surface. t is the direction vector.

In Attach File,I write my sample direction in it,you can see the green is different the purple.

Dante Liu's picture

It should be same as the purple points.
Due to this result,I guess that surface is merged.

Forum supervisor's picture

Ok Dante,

It's understood now. Your assumption is likely correct (though you do not provide your IGES file) - usually CAD models are composed of several patches (faces) that can be based on absolutely different surfaces, with absolutely different parametrization. To inspect such models (let's call them shell-based), you need to write specialized algorithms to build the trajectories correctly.

If you like to know how we can help you, please, contact us at
Best regards,
Forum supervisor