Ray-Traced Images

Ray tracing is a fascinating method of producing photo-realistic images of nearly any scene you can imagine. It lends itself especially well to surrealism and dreamscapes, especially those primarily composed of geometric objects as opposed to organic shapes, which are much more time-consuming to define, but with enough perseverance, ray tracing is fully capable of rendering pretty much anything you want. The following images were rendered using the Persistence of Vision Ray Tracer, POV-Ray. This is a fantastic freeware program now available in a 32-bit Windows version, a big step up from the command-line operated DOS versions!

The first few images shown here were created with an early DOS version of POV-Ray. Some of us made elaborate batch-files to handle the multitude of command-line options for the POV-Ray executable, and this was part of the fun at the time, but there is little doubt that the new graphical interface is a great improvement. Still, it is not for the impatient. The core of the POV-Ray program is a compiler engine which accepts a text-file input and generates a true-color image as an output. The rest of the program is the user interface where you write your scene file and do trial runs of the image rendering process to actually see how your scene is coming along.

Basically, the way it is done is to describe your scene in a simple text file with an easy-to-learn programming language. You define every detail of your virtual world, from the objects and their textures to lighting and camera angle, focal length, and lens. To make this part easier, or at least more fun, there are also companion programs available now which use a CAD-like interface so you can actually "draw" your scene in wire-frame then output the text file in POV-Ray scene language.

The final scene file, made entirely of words and numbers, is a 3-dimensional world in text format in which you can easily manipulate all the elements. By changing a number here and there, you can move the objects around to try them in different positions, or scale them to different sizes, or even adjust the textures. With a quick change of camera position you can move to any position within your scene, and by generating a series of images you can easily create animations and fly-throughs.

During the rendering process of an actual image, the compiler loads your text file and parses it into its own "view" of your scene, then begins "shooting" rays into the scene from the camera. Each pixel of the image is calculated individually by extending an imaginary ray from the viewer's eye through the camera lens and into the scene. When a ray encounters an object, the color value of the surface at that point is calculated and assigned to the pixel.

The calculated color is a function of the texture and pigment of the object and its relationship to the light source(s) and other objects in the scene, which may cast a shadow or reflect a light source, for example. If the object is reflective or translucent the resultant new rays are shot to determine the effect on the final pixel color. This process is repeated for every pixel in the view window and the output file is a true-color image in whatever resolution you have chosen.

What makes today's ray tracers especially powerful are the built-in textures that cover nearly everything you can imagine, including glass and mirror textures which display all the appropriate transmission, reflection, and refraction characteristics of light. The background for this page is a ray-traced texture. You also have the total freedom to tweak these textures to your liking, or to start from scratch and define your own. The light sources can be white or colored, point-source or plane-source. Haze and fog can be factored in to whatever degree you desire, and simple constructive and subtractive geometry techniques can be used to build complex shapes.

The downside of ray tracing has been the enormous demand on computing power, especially when there is a lot of reflection and refraction or multiple light sources in the scene. However, with the personal computer of today, it has become a practical and entertaining means for essentially anyone to generate photo-realistic images and is no longer something strictly for big main-frame computers in the electronic studios of major graphics companies and universities.

The "average" rendering time for an image cannot really be pinned down, since it varies widely according to image content, output resolution, and computer power. A fast Pentium will do a moderately complex scene within a few minutes, but scene-to-scene rendering time can very from a few seconds to many hours.

Space Blob

The earth-like planet and clouds are also ray-traced objects. Coastline features and clouds can be randomly generated with full control over things like color, transparency, edge softness, overall feature size, etc.

The Plane of Crystal Spheres

Refracting materials treat light exactly as in real-life because of the way a ray-tracer works and the fact that you define the index of refraction in the description of your object. Of course, for many materials the index of refraction is preprogrammed so all you have to do is select the material, such as quartz in this case.

Water Tentacle
inspired by the movie "The Abyss"

The natural refractive and reflective properties of water are also modeled in the ray-tracing process, which can at the same time be represented in all sorts of quite unnatural ways.

Pawns

This is one of the example scenes that comes with POV-Ray. The pawn shape need only be defined once. That part of the code is simply copied and pasted, and with a little tweak to the numbers which define position, and perhaps color or texture, you have another pawn just that quickly.

The same code can also be pasted into a different scene file altogether so objects can be shared, multiplied, tweaked, and entire databases of "stored objects" can be created and categorized.

Here is another example scene showing the use of a "bump map". An image file, in this case a Mandelbrot set fractal, is used to define a pattern of reflecting light that makes it look like a pattern of 3-dimensional bumps, even across a non-flat surface like a sphere.

You can essentially let your imagination run free, from imitating reality to illustrating dreams, from science fiction to pure fantasy.

The following give you some idea of what others have done. Some are winners of ray-tracing contests, such as the Internet Ray Tracing Competition, IRTC.

Earth Guard
Dieter Ludmann

Any digital graphic or photo can be used as an "image map" and applied to an object for texture and detail or rendered as a full-scene background. Here, a ray-traced object is rendered with detail-adding image maps on its surface in front of a real-world backdrop image map.