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Performance Issues with cylinders in new Boolean Operations in 6.9.0

Steve Lockley's picture

I have successfully upgraded to occ 6.9.0 and everything looks good and much improved in the boolean area. This multople boolean ops is a really nice feature. I have though experienced one bigish problem with cylinders cutting cylinders.

It appears that they are incredibly slow in some circumstances. It seems to be related to the resolution of the steps in IntCyCyTrim. Basically for my models the code which increments anU1 only increments it by a very small amount (~0.003) each time as aMinUexp is always small.

There is a while look at 2368
while(anU1 .....

which is looped sometimes thousands of times for simple cylinders

I have run the same ops on 6.5.4 and all runs as expected, attached are the two cylinders I am trying to cut from each other

It is a bit out of my depth to fix, does anyone have suggestions?

Steve Lockley's picture

I should also mention that after the completion the boolean operation does give the correct result, it returns the body shape

Steve Lockley's picture

Also noticed the same issues arises with semi-infinite prisms that have a face bounded by edges that are curved. In the case of these making them finiite prisms with a much smaller extrusion improves the performance. Without this the execution of a simple cut can take an hour before it fails

Forum supervisor's picture

Dear Steve,

Thank you for interesting question. In OCCT6.9.0 algorithm of finding Cylinder-Cylinder intersection differs from analogical one in OCCT6.5.4.
However, the computed small step corresponds to the ideology of existing algorithm of OCCT6.9.0. At the same time we believe that it is possible to increase performance for such cases. Therefore, I suggest you to report the corresponding issue in OCCT Mantis bug-tracker which is available via the Collaborative portal -

Best regards

Steve Lockley's picture

Thank you I have raised it on that site at
Could i just clarify if you have identified this as a bug or repeated the problem?

Forum supervisor's picture

Dear Steve,
Unfortunately it is not appropriate place for your message.
Got to RESOURCES page and open "Mantis BT issue tracker" link (
After that make "Login" and in the appeared page find label "Project:",
choose "Community" project and after "Report issue". Fill necessary fields and at the end "Submit Report".
The issue will be registered in Mantis BT.
It is not a bug, but rather specificity of the current implementation. But we believe it can be improved.
Best regards