[osg-users] Texture not clear in far view

Jean-Sébastien Guay jean-sebastien.guay at cm-labs.com
Mon Sep 8 06:18:36 PDT 2008


Hello Fangqin,

> Yes, the DDS format is a good solution to control the mip mapping. But 
> now since my texture is JPEG, it seems that I have to let OSG generate 
> mipmaps.

You can change the textures and replace them in your model, or just use 
a visitor to replace the textures and re-save your model, or... I don't 
see why that would be a problem.

If you can accept the changes in your art pipeline involved by having 
someone generate mipmaps and saving textures to a DDS file, using that 
file in a model is very easy.

> I find that the default filtering mode is LINEAR_MIPMAP_LINEAR for 
> MIN_FILTER. I tried some other filtering modes like LINEAR, and the 
> texture performance becomes better in far distance. The texture, 
> however, doesn't look very stable and is kind of dithering when you move 
> the scene. When you stop, everything is just fine. 
>  
> Any hints for the possible reason for this? Thanks a lot.

LINEAR_MIPMAP_LINEAR = mipmapping
LINEAR = no mipmapping

Look up mipmapping on Wikipedia, and you'll find the answer to your 
question.

As I said, the GLU functions that generate the mipmaps cause too much 
blurring in the textures (which is what you originally asked about). Now 
you disabled mipmapping, so you removed this blurring, but of course 
then you get the artifacts that are to be expected when mipmapping is 
not used.

Possible solutions, once again:
1. Generate the mipmaps yourself using better filtering, so that they're 
less blurred. Store the resulting texture with mipmaps in a DDS file and 
use that on your models at runtime.
2. Tell OpenGL to use a better filtering method at run-time (anisotropic 
filtering).

You haven't tried running your models through the optimizer's texture 
visitor to enable anisotropic filtering on their textures. I would 
suggest you try that if you really don't want to try creating the 
mipmaps yourself and replacing your textures by DDS textures.

Hope this helps,

J-S
-- 
______________________________________________________
Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com
                                http://www.cm-labs.com/
                         http://whitestar02.webhop.org/



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