Technical Q&A QD3D44

Quality of Video Textures

Q: We created an application similar to the TextureEyes demo distributed by Apple: it maps a moving image texture onto a spinning cube. The display quality of TextureEyes, however, is much better than ours.

We're using large high-quality textures (480x320), but the image mapped onto the cube is quite chunky even when we are using the Apple QuickDraw 3D Acceleration card, and the animation seems to be slower and jerkier. What's TextureEyes' secret?

A: No secrets! TextureEyes is a straightforward implementation of the texturing of QD3D geometries.

The problem is that your texture is actually of too high quality. QuickDraw 3D uses a tri-linear MIP map algorithm to obtain the best possible quality texture mapping.

To create a MIP map from an image requires creating sub-images sized for every inverse power of two; i.e. 1/4, 1/16, 1/32 etc. The process of creating a MIP map for every texture takes time, and larger textures will require longer. TextureEyes uses a 128X128 source for its movie and video textures.

See Also:

• For more information on MIP maps, see Computer Graphics, Principles and Practice, Second Edition in C, by Foley, VanDam, Feiner, & Hughes, 1996, Addison Wesley.