3D graphics eBook - Course Materials Repository

Photon tracing 110
Advantages and disadvantages
This method has a number of advantages compared to other methods.
• Global illumination and radiosity are automatic and nearly free.
• Sub-surface scattering is simple and cheap.
• True caustics are free.
• There are no rendering artifacts if done right.
• Fairly simple to code and implement using a regular ray tracer.
• Simple to parallelize, even across multiple computers.
Even though the image quality is superior this method has one major drawback: render times. One of the first
simulations in 1991, programmed in C by Richard Keene, it took 100 Sun 1 computers operating at 1 MHz a month
to render a single image. With modern computers it can take up to one day to compute a crude result using even the
simplest scene.
Shading methods
Because the rendering method differs from both ray tracing and scan line rendering, photon tracing needs its own set
of shaders.
• Surface shader - dictates how the photon rays reflect or refract.
• Absorption shader - tells the ray if the photon should be absorbed or not.
• Emission shader - when called it emits a photon ray
Renderers
• [1] - A light simulation renderer similar to the experiment performed by Keene.
Future
With newer ray tracing hardware large rendering farms may be possible that can render images on a commercial
level. Eventually even home computers will be able to render images using this method without any problem.
External links
• www.cpjava.net [1]
References
[1] http:/ / www. cpjava. net/ photonproj. html