GPU Path Tracer

A GPU-accelerated path tracer written in C++ using Metal via metal-cpp.

Build

From the directory containing Shaders.metal:

xcrun -sdk macosx metal -c Shaders.metal -o Shaders.air
xcrun -sdk macosx metallib Shaders.air -o default.metallib

to compile the Metal shader (Shaders.metal) into a .metallib.

From the build directory:

cmake .. -DBUILD_GPU_PT=ON
make

to build the c++ code.

Run

Move default.metallib to the build directory so the executable can find it and run:

./gpu_pt > output.ppm

References

• GPU Programming with the Metal Shading Language: A very good intro video on GPU programming with Metal
• Accelerated Ray Tracing in One Weekend in CUDA

CPU Path Tracer

A CPU-based path tracer written in C++, based on Ray Tracing in One Weekend, and extended with multithreading support.

Final Render Statistics

• Resolution: 1200 × 675
• Samples per Pixel: 500
• Machine: Apple MacBook Pro (M1 chip, 8 cores)
• Render Time:
  • Single-threaded: 6h 6m 44s
  • Multi-threaded (8 cores): 53m 42s
  • Multi-threaded (8 cores) + BVH: 8m 54s

Leveraging C++17 parallel algorithms (std::execution::par) and Intel TBB, the implementation achieves over 40× speedup in scanline rendering when combined with BVH acceleration.

Build

From the build directory:

cmake .. -DBUILD_CPU_PT=ON -DCMAKE_CXX_COMPILER=g++-15
make

to build the c++ code.

Run

From the build directory:

./cpu_pt > output.ppm