RRT is a stochastic, multithreaded ray tracer written in C++ that relies on casting a very high number of samples per pixel into the scene and then scatters diffuse rays in every direction.
The method is far from efficient and producing a noise-free image may take thousands of samples per pixel (and hours of CPU time) but it produces effects "for free" that many other ray tracers can only approximate, including:
- diffuse inter-reflection (colour bleeding)
- area lighting and soft shadow
- glossy surfaces
- depth-of-field
- caustics
The current implementation supports a limited number of 3D primitives:
- spheres (of course!)
- cubes
- infinite planes
- triangle
- triangle meshes (via Open Asset Import Library)
- compound (parent node for collections of the above)
Arbitrary homogenous transformations are supported to move and deform primitives, but as yet these transformations cannot be nested. That is to say, a compound node cannot yet have a transformation that applies to all child nodes within it.
There is no scene description language - the user has to write a C++ program that makes call to the RRT APIs that create nodes, attach shaders to nodes, etc. See the example programs in scenes/ for more details.
The most powerful shader is Shader::stochastic that can take a surface object that is similar to those used in other ray tracers and will automatically cast a single diffuse ray, a specular reflected ray and a tranmitted ray, depending on the surface's properties.
For a surface that has purely diffuse lighting properties the Shader::diffuse shader can be used instead and is slightly more efficient than Shader::stochastic because it doesn't have to consider the surface properties to decide whether to cast any non-diffuse rays.
There are no "lights" in RRT. Any object can have a Shader::constant shader attached to it that makes that object a fixed colour and indirectly causes it to "illuminate" any object that casts a ray in its direction.
RRT requires a C++11 compatible compiler, Boost, Open Asset Import Library, GD, libpng, libjpeg and libz. The supplied Makefile is for Mac OS X with macports.
Two samples scenes are included so far, "snooker" and "cornell".
The demo programs will either start a new render, or if passed a .rrt file as parameter will use that as the starting render buffer state. Every eight samples the current render buffer is rewritten to the .rrt file, as well as a 48-bpp PPM file. The netpbm package can be used to convert PPM files into PNG or JPEG, or many other formats.
- More primitives
- Bounding volume / Spatial acceleration techniques
- Compound transformations
- Time-based transformations (motion blur!)
Ensure partial frames can't end up in the.rrtfiles