Compilation and launch errors on macos

[cpichard]

Hi,
I tried to compile following the instructions and I ran into a linking issue:

Undefined symbols for architecture arm64:
  "ad_var_add(unsigned long long, unsigned long long)", referenced from:
      pxrInternal_v0_26_3__pxrReserved__::SceneModel<drjit::DiffArray<(JitBackend)3, float>, mitsuba::Color<drjit::DiffArray<(JitBackend)3, float>, 3ul>>::Render(pxrInternal_v0_26_3__pxrReserved__::HdRenderPass const*, pxrInternal_v0_26_3__pxrReserved__::HdCamera const*) in scene_manager.cc.o

I appears that those symbols are built in the library drjit-extra in mitsuba3 and drjit-extra is not linked against hdmitsuba. This patch fixed the issue.

patch.zip

After applying the patch it compiles fine. I setup the environment variables with setpath.sh, launch my application and when switching to mitsuba render delegate it crashes with:

libc++abi: terminating due to uncaught exception of type std::runtime_error: jit_init_thread_state(): the LLVM backend is inactive because the LLVM shared library ("libLLVM.dylib") could not be found! Set the DRJIT_LIBLLVM_PATH environment variable to specify its path.
Abort trap: 6

[dvicini]

Hi,

Thanks for flagging this, I've fixed this now in PR #2 . Let me know if it still causes issues.

For the second problem: Do you have LLVM installed? Does Mitsuba3 run on it's own? The error handling maybe should be improved here as well.

[cpichard]

Hi, thanks for the quick reply !
I think mitsuba builds its own llvm, is this cmake variable responsible for it ?

//Build the Dr.Jit LLVM backend?
DRJIT_ENABLE_LLVM:BOOL=ON

[dvicini]

Mitsuba does not build LLVM itself, it relies on your system having LLVM pre-installed and loading it at runtime.

The error you are getting is due to Dr.Jit not being able to locate (or load) the LLVM library at runtime. This can most likely be resolved by manually setting DRJIT_LIBLLVM_PATH to contain the full path to libLLVM.dylib.

In rare cases, e.g., on a corporate laptop, you may be in a security restricted setup that prevents some ways of loading libraries. I've encountered this myself when running usdview. If that is the case, you may need some workarounds, such as creating a helper Python script that first imports Mitsuba, sets the LLVM variant, and then launches usdview directly from the Python script:

import sys
import mitsuba as mi
from pxr.Usdviewq import Launcher

mi.set_variant('llvm_ad_rgb')
sys.argv[0] = 'usdview'
Launcher().Run()

[cpichard]

Thanks ! I don't have llm installed on my machine, that is probably the reason why. I have retried to build Mitsuba without llvm and always got an issue with cmake or the build itself. When you deactivate DRJIT_ENABLE_LLVM and DRJIT_DYNAMIC_LLVM, cmake complains about LLVMConfig missing. Just deactivating DRJIT_ENABLE_LLVM and the build fails with:

AttributeError: module 'drjit' has no attribute 'llvm'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/cyril/installs/mitsuba3/ext/nanobind/src/stubgen.py", line 1619, in <module>
    main()
  File "/Users/cyril/installs/mitsuba3/ext/nanobind/src/stubgen.py", line 1538, in main
    mod_imported = importlib.import_module(mod)

I'll try installing llvm and rebuild mitsuba with it when I got some time this week-end.

[dvicini]

Yes, you most likely are better off just installing LLVM on your machine and building mitsuba with LLVM support.