This way it doesn't has to be set in CMakeCache.txt every time the
repository is checked out.

Currently only works with the --gpu / --wavefront integrator.
WASD-style controls; could use refinement.
Control-R to record frames.

https://qoiformat.org

Normalize unicode strings for user-supplied names (objects, materials,
media, etc.)  Note that there is no need to normalize strings for things
like the name of the selected sampler, light source types, or the
parameters provided to pbrt objects, as all of the valid ones are plain old
ASCII text. We also intentionally do not normalize pathnames, as doing so
can cause all sorts of trouble.

- #undefine interface, which somehow gets #defined in debug builds, thwarting
  the layered BxDF code
- Move a CHECK out of (possibly) GPU code
- And some cmake tidying

Update filesystem/ and stb/ to latest versions.
Start using git submodules for lodepng (and update to latest.)

Every 100ms, logs CPU (and GPU, if PBRT_NVML is enabled at cmake configure
time) utilization and memory use to the verbose log.

This is currently only useful on Linux; OSX and Windows need their
system-specific calls wired up to get current CPU utilization.

Previously the build errored out with a pre-version 11 version of CUDA.
Now it, more helpfully, issues a warning and builds a non-GPU version
of pbrt.

Add "info" and "cat" sub-commands.

Beyond the convenience of having them as a vector of strings, this
is where UTF16 -> UTF8 conversion of args happens on Windows.

This led to some adjustments to ParseArg()...

With this (and a number of preceeding commits), #136 should now be fixed.

Put cpu/ source files in their own subfolder for MSVC
Add the cpu/*.h files, which weren't included in PBRT_SOURCE_HEADERS before.

Fortunately, the compiler error was fixed in 11.3.1...

(Issue #124.)

Relates to issue #100, #96, #89, and #48...

* Generalize GPU rendering path to run on both CPU and GPU

Now we have a WavefrontIntegrator that can both run on the CPU (backed by
ParallelFor() for parallelization and pbrt's aggregates for ray
intersection acceleration) and on the GPU (backed by GPUParallelFor() for
parallelization and OptiX for ray intersection on NVIDIA GPUs.)

Beyond generalizing the code, this refactor allows CPU-side debugging and
testing of the wavefront integrator.  Doing so allows further isolation of
the GPU-specific code into a few source files, now just ~2.5k lines of code.

This includes a bug fix in the wavefront medium code to resolve MixMaterials
to one of their constituent materials before enqueuing material evaluation
and shading work.

Note that on the CPU, the wavefront integrator runs 5-10x more slowly than
pbrt's regular CPU integrators, so it is not recommended for regular use...
Co-authored-by: NWenzel Jakob <wenzel.jakob@epfl.ch>

Issue #124.

- Minor changes to how hash values are computed for scrambling in the
ZSobolSampler.
- Folded util/bits.h into util/math.h.

Issue #105.

Apparently Manjaro Linux ships with an unrelated /usr/bin/bin2c.

Issue #105.

When building checkcuda nvcc might not be on the $PATH so instead rely on CMAKE_CUDA_COMPILER.

Set PBRT_DEBUG_BUILD via generator expression.

Use -march=native with CUDA builds again using a generator expression that
adds '-Xcompiler' for CUDA targets.  (Hopefully works around #87.)
This gives about a 10% perf. benefit with CPU rendering.

(Only makes sure everything compiles; doesn't run tests.)

* try 2

* ubuntu20.04

* fix

* fix

* fix

* fix

* fix

* fix

* rgb2spec speedup

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

* fix

(Related, issues #96, #89, #61, #48, and #41.)

Superceded by support for exporting to pbrt-v4 in assimp.

This isn't supported in 3.14.3, at least, but list INSERT with a 0 index is
equivalent and is available there.

(PR #73 followup)