A scene rendered by ZeroRay illustrating reflection and refraction. The glass orbs both reflect and transmit light through them.

ZeroRay began its life as a ray tracer. Building a ray tracer from scratch was one of the large projects for a graduate level computer science course I took called Image Computation. I ended up using ZeroRay in a lot of other projects and it has evolved into a ray tracer/computer vision (CV) toolkit with a suite of deep applications that are both interesting, and illustrate how to use ZeroRay.

I have released ZeroRay as open source software, under the BSD license. The BSD License is pretty much the most liberal open source license. The basic jist is that you can use the code for anything you want, be it open or closed source, commercial or non-commercial. All you have to do is give the author credit for using their library. You can visit the ZeroRay project page at sourceforge. At the time of this writing, I haven’t prepared any convenient downloadable packages so you will have to check the code out of the svn repository. To do so click Develop on the project page and follow the instructions there.

If you’re wondering, “What’s a Ray Tracer?” check out my previous article What is Ray Tracing?

Back to what exactly ZeroRay is. ZeroRay is a software library (or more precisely a set of software libraries). That means it is a set of tools that are used by programmers to create applications. A simple application could be one that, when executed, draws a pre-set picture and saves it to an image file. A more complex application could be a program that allows you to set up a 3D scene by dragging objects into it a low quality rendering of the scene and then invokes the ZeroRay ray tracer to generate a high quality version of the image. As a bit of an aside: ray tracing is a way to generate very high quality computer graphics, however it is significantly more computationally intensive than the techniques used in real-time renderers, like the sort that are used in video games. To make the ZeroRay ray tracer widely useful to computer artists (who generally are not programmers), it would need an application similar to the second example. But ZeroRay is more than a ray tracer. (more…)

An image of the statute of Athena rendered by ZeroRay.

There are two approaches to the computer graphics problem:

1. For each object in a scene, project it onto the screen, then color in all the pixels that it covers.
2. For each pixel on the screen figure out which object in the scene it points at, then color the pixel the color of that object.

The first approach is the one used by mainstream, real-time graphics toolkits like OpenGL and DirectX. The second approach is ray tracing. This may seem like a fine distinction, but this choice determines what sort of things end up being hard or easy later. (more…)