A backward ray tracer that takes in JSON scene files and outputs images.

Ever since I took a ray tracing course in college, I wanted to build one outside of the constraints of the class. I enjoy the images that ray tracers produce almost as much as I enjoy the way they're produced (as opposed to more traditional graphics engines). This project is largely a learning exercise in architecture, unit testing, and class design. I've chosen C# since it's the language I'm currently most familiar with, but I could see this slowly converting over to C++ libraries as I develop more of the project.

Thanks for stopping by!

I used Microsoft Visual Studio Community 2019 to create this project, though if you're code-savvy you might be able to compile it with whatever tools you prefer.

1. Clone the project
2. Open up rt.sln
3. Press F5

• Optional
  • Tweak dev_config.json to change how detailed you want the image, and to specify which scene you want to render.
  • Keep reading if you want to understand the specifics.

rt is nearly completely data-driven, it reads in files from the following locations in the given priority order.

1. The same directory as the exe
2. The root of the development directory, called <src_root>
3. The <src_root>\scenes directory
4. The <src_root>\scenes\unit_tests directory
5. The <src_root>\scenes\unconverted directory

Two types of files are supported, one for the config that rt takes as a command line argument, and within that file there's the specified scenes.

Config files contain information on how to generate the image. In this file you specify:

• See <src_root>\dev_config.json as an example.

• width - The number of pixels for the width of the image. The height is calculated from the aspect ratio of the projection plane in the scene file.

• renderDepth - The max number of bounces each ray can make, the higher this number the more light detail is calculated for each pixel at the cost of render speed.

• output - What you want the generated file to be called, unused currently.

• sceneFile - A list of scenes that you want to render, all of which use the same width and renderDepth values.

Scene files contain information about how the scene is constructed, specifically:

• See any file in <src_root>\scenes\ as an example.

• camera - Represents the viewpoint through which we observe the scene.

  • eyeDirection - Direction vector specifying the camera's eye position relative to the projection plane's center.
  • projectionPlane - The surface through which we view the scene, used in conjunction with the camera's eye position to generate the initial rays that we cast.
    • center - Center of the projection plane, used for per-pixel location calculations.
    • uAxis - Horizontal axis of the projection plane, length is half the width of the projection plane.
    • vAxis - Vertical axis of the projection plane, length is half the height of the projection plane.

• shapes

  • material - All shapes contain this set of properties that describe how they appear, basic explainations are given but correct terms are used if you want to search online for more info.
    • transmissionAttenuation - The type of color produced by light that goes through the object, RGB values in the range of [0, 1]
    • diffuse - The surface color of the object, RGB values in the range of [0, 1]
    • specularCoefficient - How shiny the object appears, values in the range of [0, 1]
    • specularExponent - How big the shiny dot appears, values usually >1
    • electricPermittivity - Used to calculate the air's index of refraction.
    • magneticPermeability - Used to calculate the air's index of refraction and reflection coefficients.
  • spheres - Point and radius
  • boxes - Corner point and 3 scaled direction vectors. Vectors don't need to be orthogonal, which will result in parallelpipeds.
  • polygons - List of vertices specified in a fan format (first point is the anchor, every consecutive set of 2 points after the first are used to create individual triangles with the first).
  • ellipsoids - Point and 3 scaled direction vectors. Vectors are assumed to be orthogonal.

• lights

  • points
    • transform\position - Outdated format of specifying position of the light, will be center soon.
    • color - Color emitted by the light, RGB values in the range of [0, 1]
    • radius - Size of the light, will be used in future shadow test feature.

• ambient - Ambient light diffuse color, represented by 3 floating point values in the RBG format.

• air - The medium that light travels that isn't a shape.

  • attenuation - The "color" of the air, energy is lost as light travels through a medium and air is no different.
  • electricPermittivity - Used to calculate the air's index of refraction.
  • magneticPermeability - Used to calculate the air's index of refraction and reflection coefficients.