Raytracer

A (whitted) Raytracer written in Rust. It can read in scenes from xml files and produce images or small animations as output (see Examples). This was originally written for the GFX 25S course of University of Vienna. To use the Raytracer, clone the repo, create a scene in the specified xml-schema (or use one of the example files in the scenes directory) and run the program using cargo.

Capabilities

The Raytracer uses a Whitted ray tracing algorithm. It can send out reflected-, refracted-, and shadowrays and calculates color based on some shading model (in this case phong or cook torrance). This algorithm is good at highly reflective surfaces, but not diffuse surfaces.

The Raytracer can handle spheres, more complex objects (defined by .obj files) and 4-dimensional julia sets (as described by this paper). Each object can be either shaded (using either phong or cook torrance shading models) or (with exception of julia sets) textured. For each object there can also be an arbitrary amount of transformations (translation, rotation, scaling) that are applied to the oject as they appear in the xml file.

It is also possible to use the Raytracer to create small animations. For this you will have to define additional end parameters in the xml file (for more information see the file format). Animations will always be exported as APNG files, even if --ppm was toggled.

For better performance, the Raytracer uses multiple threads for rendering (using the rayon crate). Some scenes with complex geometry can still take quite a while to render.

XML-Schema

For the base functionality the Raytracer adheres to the scheme specified here. Additionally there are some (optional) extensions that can also be specified inside the xml files:

Extensions

• Depth of Field

  • can be specified in the xml files as a subfield of the camera. It takes the focal length and the aperture size as parameters
  • <depth_of_field focal_length=".." aperture=".." />
  • Best if used with supersampling

• Cook-Torrance model

  • can be specified in the xml files insted of the phong field in the material. It takes ambient and specular coefficients, as well as the material roughness
  • <cook_torrance ka=".." ks=".." roughness=".." />

• Animations

  • can be specified in the xml files by adding the animated field to the scene, which specifies the number of frames as well as the framerate
  • <animated frames=".." fps=".." />
  • for the objects to actually change between frames, you can specify endparameters for the objects. The program will linearly interpolate between start and end parameter for each frame
  • This is supported for spheres, where endposition and endradius can be specified, and julia sets where the endconstant can be specified
  • <endposition x=".." y=".." z=".." />

• Motion Blur

  • can not be completely specified in the xml files, but requires the --blur commandline flag
  • this requires the scene to be already animated (so some objects are moving)
  • this effect does not have a custom xml file. Use one for the animations and add the --blur flag

• Julia sets

  • Can be specified in the xml files similar to spheres and meshes. They take maximum iterations, epsilon, a position, and a constant (and an endconstant if animated)
  • They support only solid materials (how would you even texture map this?)

<julia_set max_iterations=".." epsilon="..">
    <position x=".." y=".." z=".." />
    <constant x=".." y=".." z=".." w=".." />
    <!-- material and transforms -->
</julia_set>

• Supersampling
  • Can be specified in the xml files as a field for the scene. It takes the number of samples
  • this has no dedicated custom xml file, but is instead used in some of the other effects (i.e. depth_of_field)
  • <super_sampling samples=".." />

Running the Raytracer

The input file can be given via a commandline argument. So the program can be compiled and run with the following command:

cargo build --release
./target/release/ray-tracer scenes/example1.xml

For convenience I have included a Makefile that will compile the program (all will use release build and debug will use debug build) and run it with all the provided input files (excluding chess.xml)

Commandline Options

• The program exports all images as with the PNG image format by default. To export as a PPM file instead, use the --ppm flag

• For animations, the --blur flag can be used to render a singular animations with the moving objects having motionblur. If the scene has no moving objects or is just a singular image, this will have no effect.. If the scene has no moving objects or is just a singular image, this will have no effect.

• The program will save the resulting image files with the name specified in the input file in an output directory

  • The output directory can be changed using the -o (--outdir) flag
  • If the specified directory does not exist, the program will fail

• Especially a for a long running file it is nice to have some feedback that the program is doing something. For this you can run the program with the -p/--progress-bar flag to show a progress bar that shows how far along the program is

• For all commandline options run the program with the -h/--help flag

Examples