The Rendering Times - Texturing Basics

Texture Basics

By: Daniel Routh

The phrase, "Image is everything" has always irritated me. Nevertheless, it is very true in 3D. The best built shape, without the correct texturing, rarely achieves a photorealistic look. A scene of a kitchen can go from a bunch of different colored planes and indistinct shapes to a dazzling surreal picture by just adding the correct textures. One of the hard parts about working with textures is knowing which mapping method to use in TOPAS. "Should I use TILE to put this wood texture on this kitchen chair, or maybe PROJECT map will do the trick--what exactly does APPLY do anyway? Is there a reason I shouldn't use X-ray mapping for this? WHAT DOES WRAPPING HAVE OVER PROJECT MAP!!?" (The mapper in a muddle mutters madly over methods.) Well, hopefully this handy article helps your hard decisions.

PROJECT MAP

A Project map does just what it says. It projects an image ONTO an object. Imagine an overhead projector with your texture as the transparency, and the screen/wall/whiteboard as your object. Now imagine shining your overhead projector at a white beach ball. How will it look? This is exactly how it works with 'project mapping.' In my opinion, this is the most powerful of mapping tools. It has no limitations as to what objects or surfaces it can map. However, it does have the limitation of not being able to "wrap" around an object or of having nifty specialties like X-ray or Tile. An added plus is that you can Project a map onto a single polygon, an object, or an entire group. This comes in very handy sometimes.

X-RAY MAP

X-Ray mapping may take a second glance to figure out. It doesn't actually "see" through an object, as the tutorial book puts it (though you can think of it that way if you like). Instead, it acts like a project map except for one difference--it holds the map still. Where the project map, once mapped, "follows" the object around so the mapping remains the same, X-Ray mapping holds the map perfectly still where you set it. Remember that overhead projector? A project map cheats once you have mapped that beach ball and sticks at that position relative to that beach ball. Otherwise it would be pretty frustrating. The X-Ray map, however, has no such compunctions. The "overhead projector" likes it just where it is, thank you very much! If you decide to move that beach ball, it would act just like it would in real life. The image on the beach ball shifts across as the ball moves.

One of the main ways this technique is useful is in animation. Let's say you had a simple text 3D model with the words, "Aquarium" that you animated to bounce up and down. You could take a texture of an aquarium and map it onto that object. As it moved up and down, the texture would slip across it. Sometimes that's the effect you really need.

WRAP MAP

Wrap mapping is what you think about traditionally as "texture mapping." The ancient image of the sphere with a marble texture "wrapped" around it comes to mind. Wrap mapping is used to map those tough objects that Project mapping just won't do correctly. Imagine that instead of projecting an image onto a beach ball, you wanted the image to wrap all the way around it. Imagine taking some wallpaper and "wallpapering" the beach ball all the way around. A major headache, yeah, but for some reason you want to do it. You would find in the process that you had to squeeze the sections of wallpaper at the poles of the beach ball, or they would do strange things. Another analogy is to remember a picture of a correct 2D figure of the globe. You know, the type that looks like some kindergartner practiced on the edges. That's what happens to your beautiful texture when you wrap it. (Around a sphere anyway) Topas is forced to trim (actually more like squeeze) the outer edges to wrap correctly around your sphere. The principle of having to squeeze your image in certain places is the driving force behind the rest of the Wrap functions: Lathe/Spiral, Extrude, Connect/CS Model, Spline surface. The Spline surface method has never been to my liking. I know TOPAS has its work cut out for it trying to figure out random and complex spline shapes to wrap the texture onto. But in my opinion, the results of WRAP/SPLINE SURFACE are rarely satisfying. I couldn't do without WRAP map on the other functions though. They're a must.

Texture Basics Part 2

The Rendering Times: Design and Copyright © 1997 -- DCS & WorkForce Graphics. All rights reserved. Reproduction in whole or in part in any form or medium without the express written permission of DCS and/or WorkForce Graphics is prohibited.