[sldev] [SNOW] Problems with high resolution textures

Sheet Spotter sheet.spotter at gmail.com
Sat Jun 20 22:04:46 PDT 2009


An enhancement in the Snowglobe viewer may be responsible for problems with
high resolution textures. I'm hoping someone in SLDev can confirm this and
start the search for solutions.

 

Two examples of this problem are SNOW-45 (some large textures do not render
properly) and SNOW-48 (textures not resolving on megaprims). 

 

The Texture Console provided a clue to the underlying cause. In SNOW-45 and
SNOW-48 when you zoom in on the objects the "Area" column in the Texture
Console seems to be artificially limited to 4,096 or 65,536 for the
misbehaving textures. (You need to right-click and edit the object to see
its textures highlighted in the Texture Console.) In some cases the Area
value actually drops when you zoom in.

 

The new Snowglobe viewer includes optimizations that reduce the detail in
textures that are "not important to the camera". This seems to be aimed at
improving memory utilization by limiting the use of large textures when they
have no benefit. For example, when a face is "less important" it will be
drawn with only a 64x64 texture (that's where the 4,096 comes from). Larger
faces that are less important may be drawn with a 256x256 texture (that's
the 65,536 value). 

 

In the Snowglobe source code the LLFace::calcImportanceToCamera method
determines how important each face is in the avatar's camera, and the
LLFace::getTextureVirtualSize method imposes limits on the texture size
based on this importance. (The value returned by getTextureVirtualSize is
displayed in the Area column in the Texture console.) One of these two
methods seems to be responsible for limiting the detail in the textures
displayed in SNOW-45 and SNOW-48.

 

I hope someone more experienced in this area of the code can confirm these
findings, and further the cause by proposing possible solutions. A simpler
explanation of these findings will be added as a comment to SNOW-48.

 

 

Sheet Spotter

 

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