Problem with version 6.5.2


I have noted that version 6.5.2 of OpenCascade has introduced some problems displaying the model taken from here [1]. I cannot attach it here because its size (6.80 MB) is bigger than the maximum allowed size on this forum (2 MB); if you give me an email address that could accept its size I'll send you there.

In particular, if you see it using front view of Import/Export app and zooming it with the new version the surface doesn't appear right while with the 6.5.1 and with other CAD softwares it appears right.

I have the same problem with my app written with OpenCascade that uses another visualization library so probably the problem could be in the BRepMesh triangulator.

Thanks in advance and happy new year!
Francesco Argese


Forum supervisor's picture

Dear Francesco,
I would like to inform you that the posted problem has been checked and reproduced.
The OCCT version 6.5.1 has no the specified problem.
The corresponding issue with ID = 22893 has been registered.
Later you may check if the issue is resolved by checking references to the specified ID in OCCT Release Notes. The analysis of the issue will take some time depending on our technical capability and availability of resources.
If the problem is blocking for you, you may contact us via the Contact Form
You are also welcome to develop a corresponding patch and make a contribution via the Collaborative portal -

PG's picture

Dear all,

Watching the forum threads since the release of 6.5.2, it looks like this version is unstable with lots of bug's reported and registered by the supervisor. User's have reported critical issues
even in modelling algorithms of booleans's and fillet's.
Is there any new stable version planned for release ?


- PG

Forum supervisor's picture

Dear PG,
For sure not all bugs registered last time were processed and fixed.
The document "Open CASCADE Technology and Products ver. 6.5.2 Maintenance Release"
contains a list of bugs fixed in this version. If you are referring exactly to those bugs (reported as fixed) could you provide additional information which would allow us to reproduce and analyze each case.

Forum supervisor's picture

Dear PG,

We believe OCCT 6.5.2 is more stable than previous versions, even if some issues have been already recorded for it.

Among the 15 issues reported by the Community and registered in our tracker (see since OCCT 6.5.2 publication, only one declares a regression in the code (issue #22893, i.e. the one corresponding to this thread). The fact is that our test database did not contain a test case that would allow us to notice this degradation of shading quality (and now we have one thanks to the bug report from this thread). Two more issues specific to 6.5.2 (#22870 and #22865) were related to generated documentation and have already been fixed. Please, see the updated package available on the download page (as well as the corresponding issues in the Bugtracker). Other issues look (and some are explicitly described) as being also present in previouis versions.

In our understanding, the increased inflow of bug reports is due to the growing use of OCCT and the users' activity, and by no means not due to a decreasing software quality.

We will appreciate if other users can share their opinion on the quality and stability of OCCT 6.5.2 (and/or other releases).

Best regards,
Forum Supervisor

Francois Lauzon's picture

Well, we haven't had a lot of testing time yet, but the new release did solve some of the recent problems with had with the Express Mesh component, and we didn't have any issues with the others parts of OCC.

Denis Barbier's picture


I fully agree with Forum supervisor, in my humble opinion, bug activity is not caused by regressions but by a stronger interaction between users and developers, which is a very good thing.