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Calefaction

OpenGL Programatically changing LOD bios

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Is it programatically possible to change the LOD bias via OpenGL? I am assuming it would be a card specific extension (as the setting is a driver setting), but I can't seem to find any information about it. Has anyone done this programatically?

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Guest Anonymous Poster
You can change lod bias in OpenGL vertex programs (ARB and GLSL)

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u dont need vertex programs
from memory texture_lod_bias came it with opengl1.2 or 1.3
look it up in the spec

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Nevermind, I found it. OpenGL 1.4, GL_TEXTURE_LOD_BIAS. How is it used though? glTexParameterf seems to be rejecting it, is it a texture environment setting?

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Quote:
Original post by Calefaction
Hmmm, I can't find much about texture_lod_bios, is it an NV extension?


It's an EXT extension (used to be SGI or SGIX): GL_EXT_texture_lod_bias

It's pretty straightforward to use:


glTexEnvf(TEXTURE_FILTER_CONTROL_EXT, TEXTURE_LOD_BIAS_EXT, foo);

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Its an EXT extention, google provides: Linky.

Theres another (more useful IMHO) extensions for clamping the mipmap selection to a range, but I can't remember the name of that one offhand.

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Thanks, I got it working :) For now I am just implementing the LOD bias, eventually I will look in to implementing the clamp ranges :)

Also, this was incorporated in to OpenGL 1.4, so you don't have to use it as an extension anymore :) Provided they have an OpenGL 1.4 compliant driver of course.

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