TITLE: "Full Spectrum" NAME: William Bobzien COUNTRY: USA EMAIL: bobzien@acpub.duke.edu TOPIC: Physics & Math COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT. JPGFILE: wbspctrm.jpg ZIPFILE: wbspctrm.zip RENDERER USED: POV-Ray 3.01 for Windows TOOLS USED: Paint Shop Pro 4.12 (JPEG conversion and signature) RENDER TIME: 9 minutes 17 seconds HARDWARE USED: P166, 16 Mb RAM IMAGE DESCRIPTION: The classic high-school optics demonstration: a beam of white light is narrowed by a card with a slit in it and then strikes a prism; because the shape and refractive qualities of the prism bend the wavelengths by different amounts, the light is split into its component colors, which show up as a spectrum on another card. DESCRIPTION OF HOW THIS IMAGE WAS CREATED: All objects in this scene are either primitives or CSG objects. Ironically for a ray-traced image (and one about the properties of light, no less), there are no lights in this scene! As I recall from my (ever more distant) high-school days, this type of demonstration works best in a darkened room. Of course, no classroom can be made easily light-tight, so some dim illumination creeps in from under doors, between the slats in the window blinds, etc. At first, I had a dim spotlight shining down on the demonstration, but I couldn't keep it from looking like, well, a light shining down, so I eliminated it and just started playing with ambients. That only worked so well, with all areas of each object equally bright (i.e. flat-looking objects), so I finally got around to trying out texture_maps, to vary the ambient level across the objects. The worst problem with dropping the light was that I lost the pebbled surface on the body of the "light source" that I had created with a normal perturbation. With the light it looked just like the rough surface I remembered from similar equipment in school, but I was only able to imitate the look with ambient tricks, not duplicate it. I also lost the nice phong highlight on the "lens." It was a case of increasing realism in one area by decreasing it in another. Initially, I had a spotlight shining from the light source to the "slit card," which worked great, right up to the part where it plowed through the "prism" like it wasn't there and kept going. So I dropped that light too. I used halos at first for the "beam" and the horizontal "spectrum," but they didn't work any better than using gradients, at least not when one considers the increase in rendering time. Also, it was hard matching the horizontal spectrum halos to the gradient I was already using, out of necessity, for the vertical component of the spectrum. So I eventually went to gradients for everything that was supposed to be a "light." I had a lot of fun creating this image, and learned a lot as well about texture and pigment patterns. For example, I had never used the "onion" pattern before this image. I deliberately avoided using "canned" textures from textures.inc etc. I did mostly use pre-defined pigments from colors.inc.