POV-Ray Persistence of Vision Ray Tracer How to make realistic graphics images on your personal computer.

1.0 What is POV-Ray

To create a picture, a scene must first be defined mathematically in three-space using simple POV-Ray commands. These commands are similar in syntax to the C programming language. By applying laws of math and physics, the ray tracing program then calculates what the scene should look like. For every pixel on the screen, a ray of light is traced from a hypothetical camera source, backwards through the scene, carefully determining the cumulative effects of every object it might have encountered along its way. POV-Ray can handle very complex environments, such as reflections off of shiny or dull surfaces, refraction of light through transparent or translucent objects, patterns from textured surfaces or graphics, and the effects of shadows and multiple light sources. Artists will have difficulty matching the photographic realism that POV-Ray handles with ease, but a knowledge of art principles can help programmers produce very attractive computer graphics with ray tracing.

In every POV-Ray scene, there are three essential elements:

1. A camera to take the picture
2. A light source to illuminate the scene
3. Some objects to draw

2.0 POV-Ray Resources

• The On-line POV-Ray Tutorial - A winning ThinkQuest project developed by some former Jefferson students.
• The Official POV-Ray Homepage - Includes latest releases of POV-Ray binaries for a variety of computer systems.
• Getting Started with POV-Ray - Introductory materials and answers to frequently asked questions.

3.0 Creating an Image Using POV-Ray

Here is an example command line to run the ray tracer.

x-povray   -Isphere1.pov   +V   +D0   +P   +X100   +FP16   +Osphere1.ppm   -H240   -W320

This command runs x-povray, the X-Windows version of POV-Ray, on our LINUX systems in the CS Lab at Jefferson. The following options were used:

-I     Include the source file sphere1.pov
+V     Give Verbose output as the rendering is proceeding
+D0     Display the picture to the console as it is being generated
+P     Pause for input from the mouse before erasing the image
+X100     Enable eXit after every 100 pixels in case the user wishes to terminate the rendering.
+FP16     Generate a PPM File in 16 bit color
+O     Give the Outfile the name sphere1.ppm
-H240     Make the Height 240 pixels
-W320     Make the Width 320 pixels

At the same time POV-Ray is writing an image to the screen, it is also writing an image file to disk. In this example, the file will be called sphere1.png and will be in the "PNG" file format (Portable Network Graphic). We typically use the program xv for manipulating or printing graphics files but for files conversions from this file format, try using ee (Electric Eyes). The program ee is very easy to use for converting between many file formats but doesn't have as many built-in editing tools.

• mypov - generates a small graphic image in ppm format (Portable PixelMap), and moves the file it generates into a directory called "images"
• bigpov - generates a larger graphic with better quality and moves it to a directory called "images"
• clockpov - generates a PPM file using the clock variable that also becomes part of the file name but leaves the result in the same directory.

4.0 Some Classroom Examples

	Sphere 1: This program generates a simple shiny red sphere floating over a black and white checkerboard plane. It is the equivalent of "Hello World" in POV-Ray. Source Code
	Sphere 2: This program adds a second sphere, but the new object has different properties. It is light blue and transparent, showing how light is refracted through the glass like substance. Source Code
	Sample Objects: In addition to a shiny red sphere, this program draws a variety of other objects including a yellow metallic box with a textured surface, a blue glass torus that intersects the box, a green cone with a portion removed, and a white blob formed as a union of several spheres. The blob has a scanned image of one of the author's floral paintings wrapped around its surface. Source Code     and     Floral Painting GIF file

5.0 Some Student Projects That Used POV-Ray

Kristina Foster	Mandelbrot Sphere Kristina created an animated image by taking a fractal of the Mandelbrot Set, wrapping it around a sphere, and then adding waves and turbulence to the scene. More about Kristina's Life at TJ and Supercomputing
Dan Haspel	Mandel Turtles Dan created a pool scene where the black images of the Mandelbrot set appear to swim across the pool. The angle of the sun changes throughout the animation casting changing shadows from the umbrella. More on Dan's Projects and Cool Stuff
Adrian Porter	Bouncing Balls Adrian created a field of metallic spheres that rise and sink around a single stationary sphere in the center of the plane. More of Adrian's Amazing Webpage and Cool Graphics
Eamon Walsh	Stonehenge Eamon created a 3-D tour of Stonehenge as an animation in POV-Ray. More about Eamon and Great Supercomp Projects
David Rosenthal	DaveRay Rather than using POV-Ray as a ray tracer, Dave decided to write his own. He included some features that POV-Ray does not handle well such as "soft shadows". More on the Graphics Wizard Dave and DaveRay
Nicole DesRosiers	The Hall Nicole's first POV-Ray program was an animation of a dream sequence, walking down a hall with the door opening. More of Nicole's Imaginative Grapics
Mark Hibbard	Mirrored Disco Balls Mark created a sparkling set of mirrored balls that reflected various colored lights. More of Mark's Neat Stuff