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RTOW-OptiX (my OptiX version of Pete's 'Ray Tracing in One Weekend' series)


This project aims at providing a Optix Version of the 'final chapter' example in Pete Shirley's "Ray Tracing in one Week-End" series.

If you haven't read that book yet, you should (have a look here: ).

For reference, Pete's original C++ code is here:

Note this project covers only the final chapter example; Pete and I are in parallel working on a more complete OptiX-version of Pete's entire book series, but that might take a while yet.

Some random notes

  • I tried to follow Pete's original example wherever I could. I did take the freedom to clean up a few things, such as using longer (ie, more meaningful) variable names and caml-case to improve readability; or using float-constants more consistently (eg, "1.f" vs "1" or "1."); etc... but kept with his blueprint were possible.

  • There are multiple ways of realizing this example in OptiX; in particular the recursion found in Pete's example could be realized in multiple ways that would be more efficient, faster, more elegant, etc. However, as said before I tried to follow his example as well as I could, so this is my version. I'll probably provide a iterative version soon as well, but for now that should do.

  • In terms of performance, this version "should" be way faster than either Pete's CPU version or Roger Allen's CUDA version (see for that one); this is not because of any magic I might have done, but simply because OptiX will automatically build an acceleration structure over all those spheres, whereas their examples didn't. The magic of OptiX, I guess :-).


To buidl this project, you need

  • a install of CUDA, preferably CUDA 10. Make sure to put your CUDA binary directory into your path.

  • a install of OptiX, preferably (ie, tested with) OptiX 5.1.1. Under Linux, I'd suggest to put a export OptiX_INSTALL_DIR=... into your .bashrc.

  • the usual compiler and build tools - gcc, clang, etc.

  • cmake, version 2.8 should do.


This project is built with cmake. On linux, simply create a build directory, and start the build with with ccmake:

mkdir build cd build cmake .. make

Assuming you have nvcc (CUDA) in your path, and have set a OptiX_INSTALL_DIR environment variable to point to the OptiX install dir, everything should be configured automatically.

On windows, you'll have to use the cmake gui, and make sure to set the right paths for optix include dirs, optix paths, etc.


Just run the ./finalChapter binary (finalChapter.exe on windows). This should render a finalChapter.ppm image. To change image resolution (default 1200x800), number of samples (default 128), etc, just edit FinalChapter/finalChapter.cpp.

Code Overview

  • The main host cost is in finalChapter.cpp. This sets up the optix node graph, creates and compiles all programs, etc.

  • All OptiX device programs are in FinalChapter/programs/, sorted by for the ray generation program (the main render launch), for the sphere intersectoin and bounding box codes, and metal/dielectric/ for the three material types, with some helper code in vec.h (vector math), sampling, random number code, etc.

  • The finalChapter/CMakeLists scripts sets up the build; in particular, it defines all the cmake rules for compiling the device programs, embedding them into host object files, and linking them to the final binary.

  • There are two versions of the code - a 'iterative' one, in which the materials execute the scattering event, but the tracing of the path itself is done iteratively in the ray generaiton program; and a 'recursive' variant in which the materials themselves recursively trace the path on. The recursive one is closer to Pete's original example code, but of course, requires a lot of stack per pixel, which isn't cheap. The iterative version is thus "better" for a GPU, but the recursive version shows that you can most definitely use recursion if you need to (just make sure to set the stack size accordingly).

I'll write a more "tutorial" - style version that explains the high-level concepts in a separate place (likely my blog, on


  • 11/16/18 Initial Release


OptiX version of Pete Shirley's "Ray Tracing in One Weekend" (Final Chapter example only)




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