Raytracer

Small raytracer showcasing various acceleration methods on a single core processor for ray-triangle intersections tests It showcase :

• grid structure
• kdtree with various build heuristics
  • Median space split
  • Median geometry split
  • SAH (build either by the normal way, or by Igo Wald O(nlogn) algorithm)

Compile :

You must have sfml2 and python3-dev installed. You might change the link to python's header files in the makefile To build:

make

Use :

To use it, you must provide a json "scene file". Its structure will be explained below. If you need, a blender addon can generate it for you (the addon is python/blenderexporter.py). If the scene name is scene.json, you can launch the raytracer with :

./raytracer scene.json

For more complexe use, you can provide arguments after the scene file. These arguments can be :

• -t to choose a traversal method for kdtree exploration. rec means it is done recursively, otherwise it is iterative
• -i to determine the cost Ki of a ray / triangle intersection test
• -p for an approximation of the cost Kt of traversal
• -c can be use when the selected heuristic is sah and the acceleration structure is a kdtree. It can have several values : nlogn, nlog2n, nlog2nc or n2. It determines the variant of the heuristic we use to build the structure (nlogn refers to Igo Wald methods, nlog2n to the classic one, nlog2nc is the classic method but with a better sort in theory and n2 the trivial method)
• -h for the build heuristic when using a kdtree. Either geometry, (splits on the middle of the geometry) spatial (split on the middle of the space) or sah (split taking into account both the geometry and the space)
• -m the acceleration structure used (kdtree for a kdtree, grid for a grid, moller for the naive method using moller's intersection test and naive for a very naive method with a non efficient intersection test)
• -s to determinate the dimension of the grid
• -t to put a limit on the execution time (by default 120)

Examples :

./raytracer scene.json -t 90 -i 30 -p 5 -c nlogn -h sah -m kdtree

It will render the scene using a kdtree build with sah nlogn algorithm, taking Ki=30 and Kt = 5. The time limit is set to 90

By default, ./raytracer scene.json acts the same way has :

./raytracer scene.json -t rec -i 20 -p 15 -b seq -c nlogn -h sah -m kdtree -s 10 -o sfml -t 120

scene file format

A scene is a json file under the form :

{
    "SCENE_PRESETS": {
        "height": "height of the image",
        "width": "width of the image"
    },
    "OBJECTS": {
        "path": "path to the file containing the geometry (by default in obj)"
    },
    "CAMERA": {
        "fov": "fov of the camera",
        "ratio": "ratio of the camera",
        "matrix": "4x4 matrix representing the position/rotation/scale of the camera"
    }
}