Building under MacOS fails: fatal error: 'fp.h' file not found

[pixelsandpointers]

Hi @ all,

I have tried building Mitsuba (master and stable branch) on MacOS following the build tutorial:

1. gh repo clone mitsuba-renderer/mitsuba3 && cd mitsuba3 && git submodule update --init --recursive.
2. mkdir build && cd build && cmake -G Ninja ..
3. Edited the mitsuba.conf to default to llvm_ad_spectral with the following enabled variants: ["scalar_rgb", "llvm_ad_rgb", "llvm_ad_spectral"]
4. ninja

This will result in:

Sorry if the mistake is on my end, but thanks for looking at it.

– Ben

---

System information:
MacOS 15.5 (24F74)
Xcode 16.3
Build version 16E140
Apple clang version 17.0.0 (clang-1700.0.13.3)
Target: arm64-apple-darwin24.5.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
CMake 3.31.6
Python 3.12.9

[njroussel]

Hi @pixelsandpointers

Apparently libpng can no longer be compiled on MacOS since this llvm/llvm-project#74676 PR (source).

That commit was first made available in LLVM 19, which according to this table became available in Xcode 16. Currently, our CI is running v13.x.

I think we just need to update our libpng fork.

[pixelsandpointers]

@njroussel not sure how I can help you with this, so I tested it locally.

I just bumped the version of libpng to their default branch (libpng16) and applied the patches as seen in your commit to it and it builds successfully and renders.

➜ mitsuba ../resources/data/scenes/cbox/cbox-spectral.xml
2025-06-26 15:43:15 INFO  main  [mitsuba.cpp:334] Mitsuba version 3.6.4 (stable[7277c7f0], Mac OS, 64bit, 12 threads, 4-wide SIMD)
2025-06-26 15:43:15 INFO  main  [mitsuba.cpp:335] Copyright 2024, Realistic Graphics Lab, EPFL
2025-06-26 15:43:15 INFO  main  [mitsuba.cpp:336] Enabled processor features: llvm fma neon aarch64
2025-06-26 15:43:15 INFO  main  [xml.cpp:1379] Loading XML file "../resources/data/scenes/cbox/cbox-spectral.xml" with variant "scalar_rgb"..
2025-06-26 15:43:15 INFO  main  [xml.cpp:628] Loading included XML file "../resources/data/scenes/cbox/fragments/base.xml" ..
2025-06-26 15:43:15 INFO  main  [xml.cpp:628] Loading included XML file "../resources/data/scenes/cbox/fragments/bsdfs-spectral.xml" ..
2025-06-26 15:43:18 INFO  main  [xml.cpp:628] Loading included XML file "../resources/data/scenes/cbox/fragments/shapes.xml" ..
2025-06-26 15:43:19 INFO  main  [Scene] Embree ready. (took 12ms)
2025-06-26 15:43:19 INFO  main  [xml.cpp:1397] Done loading XML file "../resources/data/scenes/cbox/cbox-spectral.xml" (took 4.353s).
2025-06-26 15:43:19 INFO  main  [SamplingIntegrator] Starting render job (256x256, 256 samples, 12 threads)
Rendering [============================================================================] (2.25s, ETA: 0ms)
2025-06-26 15:43:22 INFO  main  [SamplingIntegrator] Rendering finished. (took 2.251s)
2025-06-26 15:43:22 INFO  main  [HDRFilm] ✔  Developing "../resources/data/scenes/cbox/cbox-spectral.exr" ..

Maybe this helps.

[njroussel]

Thanks, it's great to have that confirmed.

I've opened #1647 for this.

[pixelsandpointers]

Thanks for looking into it!