Newer version of OpenCascade

[AugustusGreenwood]

Problem

The newer versions of OCC reworked some of their library functionality into different libraries. FEBioStudio currently loads the following libraries that are no longer offered with that name:

• TKSTL
• TKIGES
• TKSTEP
• TKSTEPBase

They have been replaced with the following (up to the current development version 7.9.0):

• TKDEIGES
• TKDESTEP
• TKDESTL

Proposed fix

I made the change on this line (155) in the CMakeLists.txt file to successfully build and run with the new version:

- set(OCCT_LIB_NAMES TKernel TKGeomBase TKTopAlgo TKPrim TKMesh TKMath TKBRep TKSTL TKFillet TKBO TKIGES TKSTEP TKSTEPBase TKXSBase TKG3d TKLCAF TKVCAF)
+ set(OCCT_LIB_NAMES TKernel TKGeomBase TKTopAlgo TKPrim TKMesh TKMath TKBRep TKFillet TKBO TKXSBase TKG3d TKLCAF TKVCAF TKDEIGES TKDESTEP TKDESTL)

With the proposed fix I was able to load, save and merge OCC objects with no other major changes to the codebase.

Would there be any interest in merging a pull request with this change?

[michaelrossherron]

We currently build against OCC version 7.7.2. The newer versions of OCC don't offer any new functionality that we currently need, and, as far as we're aware, version 7.7.2 doesn't have any bugs in the functionality that we use.

Updating to a new version of OCC would require changes to our build systems and require that we distribute new OCC binaries via our auto-update mechanism to all of our users. This is a particularly annoying task with OCC since OCC compiles to a large number of binaries, and we'd need to be sure to distribute new copies of all of them.

Our philosophy in regards to our third-party libraries is to stay on a common standard version until we either need new functionality offered by newer versions, or we become aware of bugfixes in newer versions. This simplifies our build and distribution mechanisms considerably, and ensures that we don't accidentally introduce new bugs via our third-party libraries.

Normally, this doesn't prevent users from compiling against newer versions of these libraries if they want, but since OCC reworked their library structure, it's caused problems for people trying to link to the latest OCC versions.

Our current recommendation is to link against OCC 7.7.2. You can clone their source from their GitHub, and then checkout tag V7_2_2, and build the binaries.

That being said, I could probably add some conditional flags into our CMake file to allow users to link to either the new or the older versions of OCC. It might be a bit before I have time to get to that, however.

Hopefully that helps. Please let me know if you have any questions.

Michael Herron