A portable GPU path Tracer library running powered by SYCL. (OpenCL/CUDA/OpenMP)

About

This is a GPU path tracer library running on top of SYCL. It aims to be simple, fast, portable, capable of rendering without a GPU, and have minimal dependencies.

To compile Tracer, you need:

1. A SYCL implementation. ComputeCpp CE is best one available currently so this is what Tracer uses.
2. CMake
3. GoogleTest (for building tests)
4. (Prefered) A OpenCL accelerated or CUDA device.
   • ComputeCpp will fallback to a cpu based implementation if needed (powered by OpenMP)

Tracer's runtime requirements

1. A OpenCL/CUDA runtime
2. Tracer will fallback to OpenMP in the absence of a OpenCL/CUDA runtime.

Building

While Tracer is a library, a simple main file is used for rendering scene files. To build Tracer (on GNU/Linux) first download and compile ComputeCpp CE. Take note of where the root directory of ComputeCpp is, you will need it later.

Now in Tracer's root directory, run:

mkdir build
cd build
cmake ../ -DComputeCpp_DIR=/home/me/path/to/ComputeCpp-root-dir
make

If build succeeded, you will find two exe's in the build directory. tracer and tracer_test. The first will render scene files and the second is the tests.

Rendering a Scene

To render a scene from a scene file. Simply run. For final renders, I recommend at least 25,000 samples per pixel for a high quality output image.

cd build
./tracer /path/to/scenefile.txt samples_per_pixel

The rendered scene will output in the current working directory to scenefile.png.

Rendering with Included Scenes

cd scene_files
../build/tracer scene00.txt samples_per_pixel

Additional rendering options

You can choose to set a different image with and height then what is in the scene file. forceHostCPU ignores the GPU and any OpenCL devices and will render using OpenMP. This is useful for debugging.

Usage: ./raytracer scenefile.txt samples_per_pixel [image_width] [image_height] [forceHostCPU]

For example, ./raytracer scenefile.txt samples_per_pixel 600 600 1 will render a 600x600 image on the CPU using OpenMP.

Running the tests

Simply run tracer_test after building.

cd build
./tracer_test

Scene Files

Scene files are text files that setup the scene for rendering. (Camera, objects, materials, positions, etc.). The following is an example of a very basic scene file. It renders a single sphere light source in the center of the screen. Since there are no other objects in the scene, it is not very interesting.

# setup camera
eye 50 50 220               # x,y,z of where the camera's eye is located
look 50 50 50               # x,y,z of where the camera is looking
up 0 1 0                    # up for the camera (is the camera upside down?)
d 100                       # the focal length of the camera
bounds -50 -37.5 50 37.5    # the bounds of the image plane (the size, in world coords, of the image)
res 1024 768                # the resolution of the output image

# glowing sphere in the scene
#         x  y  z   r     emitted rgb    color rgb    material type
sphere    50 50 50  10     12 12 12       0 0 0            0

For more example scene files, see the scene_files directory.

Scene files must have all of the following attributes defined Tracer cannot render: eye, look, up, d, bounds, res.

Available sphere material types:

0 -> perfect diffuse 1 -> perfect reflection (mirror) 2 -> perfect reflection and refraction (glass)