Overview of the Visualize fx graphics

33
May 1998 • The Hewlett-Packard JournalArticle 4 • 1998 Hewlett Packard Company
Figure 2
A shadow texture image.
Figure 3
A specular lit texture image. Correct specular lighting of
textured images can be achieved with VISUALIZE fx
4
and
fx
6
texture mapping options.
article. Having a centralized daemon process manage the
cache allows for cache efficiency, parallel handling of texture
downloads while 3D graphics rendering is occurring, and shar-
ing textures among graphics contexts.
The VISUALIZE fx
4
and VISUALIZE fx
6
texture mapping
options incorporate the second generation advances in virtual
texture mapping. Full OpenGL 1.1 texture map hardware sup-
port has brought about dramatic improvements in texture
map download performance and switching between texture
maps and new extended features such as 3D texture mapping,
shadows (Figure 2), and proper specular lighting on textures
(Figure 3). These features have made these products very
appealing systems for texturing applications on workstation
graphics.
The texture mapping performance on these systems is very
competitive. The VISUALIZE fx
6
texture fill rate is about twice
that of the VISUALIZE fx
4
texture option. However, fill rates
alone do not describe how these systems perform in a true
application environment. Aggressive texture mapping applica-
tion performance comparisons show two to three times per-
formance superiority over similarly priced graphics workstation
products.
Texture Chip
The texture chip is responsible for accelerating texture
mapping operations. Towards this end, it performs three
basic functions:
H Maintains a cache of texture map data, requesting cache
updates for texture values required by current rendering
operations as needed (see “Fast Virtual Texturing” on
page 32)
H Generates perspective corrected texture coordinates
from plane equations representing triangles, points, or
lines
H Fetches and filters the texture data as specified by the
application based on whether the texture needs to be
magnified or minimized to fit the geometry it is being
mapped to and passes the result on to the raster chips.