Pov-Ray | Design

Reference tutorial guide

http://www.povray.org/documentation/3.7.0/t2_2.html#t2_2

Introduction

The Persistence of Vision Ray-Tracer creates three-dimensional, photo-realistic images using a rendering technique called ray-tracing. It reads in a text file containing information describing the objects and lighting in a scene and generates an image of that scene from the view point of a camera also described in the text file. Ray-tracing is not a fast process by any means, but it produces very high quality images with realistic reflections, shading, perspective and other effects.

What is Ray-Tracing?

Ray-tracing is a rendering technique that calculates an image of a scene by simulating the way rays of light travel in the real world. However it does this simulation backwards; in the real world, rays of light are emitted from a light source and then strike objects. Some of the light rays then bounce off the objects and enter our eyes (or perhaps a camera). However, most of the rays never reach anything that 'observes' them; they either leave the area of interest or are absorbed by objects within it.

Because the vast majority of rays never reach an observer, it would take a very long time for software to trace even a simple image if the rays were cast as they were in the real world (because almost all of the calculations would end up going to waste). For the purposes of drawing a representation of a scene as viewed from an imaginary camera, we are generally only interested in rays that reach that camera's lens.

A 'scene' is the virtual world which you wish to take a 'picture' of with our simulated camera. There can be (and usually are) objects in the scene that do not appear in the final image, just as objects outside the field of view of a real camera do not directly appear in the final image. (They can still cast shadows or be seen as reflections, though).

Accordingly, ray-tracing programs like POV-Ray start with their simulated camera and trace rays backwards out into the scene. The user specifies the location of the camera and the type of lens it is using, the light sources that illuminate the scene, the objects within it, as well as the surface texture properties of objects, their interiors (if transparent) and any atmospheric media such as fog, haze, or fire.

For every pixel in the final image one or more viewing rays are shot from the camera into the scene to see if it intersects with any of the objects in the scene. These "viewing rays" originate from the viewer (represented by the camera), and pass through the viewing window (representing the pixels of the final image).

Every time an object is hit, the color of the surface at that point is calculated. For this purpose rays are sent from that point to each light source to determine the amount of light coming from that source. These "shadow rays" are tested to tell whether the surface point lies in shadow or not. If the surface is reflective or transparent new rays are set up and traced in order to determine the contribution of the reflected and refracted light to the final surface color.

Special features like inter-diffuse reflection (radiosity), atmospheric effects and area lights make it necessary to shoot a lot of additional rays into the scene for every pixel.

What is POV-Ray?

POV-Ray™ is short for the Persistence of Vision Raytracer™, a tool for producing high-quality computer graphics. POV-Ray is Free Software (as per the definition of the Free Software Foundation) as its source code is licensed under the Affero General Public License (AGPL).

POV-Ray was developed from DKBTrace 2.12 (written by David K. Buck and Aaron A. Collins) by a bunch of people (called the POV-Team™) in their spare time. The headquarters of the POV-Team is on the internet (see Where to Find POV-Ray Files for more details).

The POV-Ray package includes detailed instructions on using the ray-tracer and creating scenes. Many stunning scenes are included with POV-Ray so you can start creating images immediately when you get the package. These scenes can also be modified so you do not have to start from scratch.

In addition to the pre-defined scenes, a library of pre-defined shapes and materials is provided. You can include these shapes and materials in your own scenes by just including the library file name at the top of your scene file, and by using the shape or material name in your scene.

Features

Here are some highlights of POV-Ray's features:

Easy to use scene description language.

Large library of stunning example scene files.

Standard include files that pre-define many shapes, colors and textures.

Very high quality output image files (up to 48-bit color).

Create landscapes using smoothed height fields.

Many camera types, including perspective, orthographic, fisheye, etc.

Spotlights, cylindrical lights and area lights for sophisticated lighting.

Photons for realistic, reflected and refracted, caustics. Photons also interact with media.

Phong and specular highlighting for more realistic-looking surfaces.

Inter-diffuse reflection (radiosity) for more realistic lighting.