Microsoft KB Archive/159989

= Microsoft Knowledge Base =

Achieving Full Resolution of Textures in GL/OGL Shade Mode
Last reviewed: November 27, 1996

Article ID: Q159989

The information in this article applies to:


 * Softimage 3D for IRIX, version 3.51
 * Softimage 3D for Windows NT, version 3.51

SUMMARY
The following information is designed to show you how to maximize the resolution of your textures in the GL/OpenGL shade view and how the new environment variable SI_SHADE_TEXSIZE_LIMIT improves shade view texturing accuracy.

GL and OpenGL can only work internally with textures that have dimensions that are powers of 2 in each direction. For example, they do not work with 800x600, but they do work with 1024x1024, or 512x512, or 1024x512, etc. In Softimage 3D 3.5 and earlier versions, textures are scaled down to the next smallest power of 2 for each dimension. So, if you have a 1200x1000 texture, it is automatically scaled down to 1024x512.

To guarantee that the textures in the shaded view are exactly what you want, make sure that your textures have dimensions that are already powers of 2 (that is, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, etc.). To prevent quality loss, scale them up to the next power of 2.

There is a new feature in Softimage 3D 3.51 that provides improved shade view texturing accuracy and faster texture definition. Generally, the larger the texture is, the slower it is to work with. To make the shade view quicker and more interactive, textures are automatically scaled down to the next smaller power of 2, and are subject to a maximum size limit (256 for each dimension). For example, a texture that is 1200x200 is automatically scaled down in memory to 256x128.

You can change the default behavior of Softimage 3D 3.51 and up by modifying the SI_SHADE_TEXSIZE_LIMIT environment variable. The following examples show the effect that different values have on the texture:

setenv SI_SHADE_TEXSIZE_LIMIT 0

- This turns off the new 3.51 feature. It will now behave like earlier versions of Softimage 3D. However, your textures must still have power-of-two dimensions, to prevent quality degradation in the shaded view.

setenv SI_SHADE_TEXSIZE_LIMIT 1024

- This changes the maximum limit on texture size from the default 256 to 1024.