Let's try some image mapping and bump mapping on this cylinder next. We'll see a problem and overcome it. C'mon...

1.) Copy figure 49 to your image editor and precisely crop the two images and save them as Blob01.bmp and Blob01m.bmp (the "m" is an extension for "mask"; if you collect zillions of texture files, the "m" helps you quickly find greyscale bump maps. I guess you could use a "b" instead, too) The image should be perfectly square.

2.) Load the blob01 image in the TextureMap panel, as shown in figure 50. Set the number of vertical and horizontal repetitions to 3, because why not? Fill and render the cylinder. As you can see in figure 50, the top of the cylinder has a mapping problem. Oh, ****. Rotate the cylinder toward you to see what I'm going on about here.

3.) When a cylindrical mapping doesn't work on a cylinder, there is absolutely no reason why you can't choose a different mapping type. Click on the UV mapping tool (the swimming goggles on the sphere drawing), and choose Spherical mapping.

4.) With the Rotate tool, make sure the mapping wireframe's polar ends are perfectly at a perpendicular angle to the front of your view. This is a tough one to describe.

What is happening is that you are removing from your current view the polar caps where a sphere mapping will "pucker" the 2D image map. From your view of the cylinder (make sure you've got the cylinder pointing toward you for maximum effect...."3D" is diminished in visual "pow" if you don't try to show more than one perspective point of the object).

5.) Render the cylinder now. Pretty neat, huh? Now, this is a "patch" but not a perfect solution to the cylinder mapping problem.

If you move the cylinder around in 3D space now (use the Object Rotate tool), you might see the "pucker" point(s) on the surface, but the pattern is pretty obnoxious and complex, helping to disguise it a little.

What, oh, what would be the perfect mapping solution? You'd need a three-piece cylinder-a top disk, a bottom disk, and then the cylinder. You'd map the cylinder cylindrically, and use a linear mapping on the top and bottom disks. And I guarantee it would take hours, because there will be an edge discontinuity where the disks meet the cylinder.

That's about it for this series of lessons, but stay tuned, because there's more to learn, and I have more to write!

--Gary David Bouton


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