opengl texture lod bias adjusting via opengl function call?

Question

how is it possible to change the lod bias via an opengl function call? i dont like the default settings, changes the miplevels too early and makes the nearby ground look ugly.

i couldnt find any codes to do this, every topic was about some external programs that does the job...

Edit: This is my texture settings:

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST_MIPMAP_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_NEAREST);

Answer 1

Use:

glTexEnvf(GL_TEXTURE_FILTER_CONTROL, GL_TEXTURE_LOD_BIAS, bias);

More details here: http://www.opengl.org/sdk/docs/man/xhtml/glTexEnv.xml and there: http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_lod_bias.txt

EDIT:

Ok, I see. First GL_TEXTURE_MAG_FILTER can only take two possible values:

• either GL_NEAREST
• or GL_LINEAR

So use GL_LINEAR for the best result.

Then for GL_TEXTURE_MIN_FILTER, with GL_NEAREST_MIPMAP_NEAREST you are using no texture interpolation, only mipmaping (you take the nearest mipmap that suits the best, but inside this mipmap you take the nearest texel only, without interpolation between this texel and his neighbours).

So use GL_NEAREST_MIPMAP_LINEAR for doing this weighted average between the texels.

With GL_LINEAR_MIPMAP_LINEAR you can have even more rendering quality since it will use a linear interpolation between the result of the texture fetch for two mipmaps (mipmap N and N+1) instead of just taking the result of the texture fetch for mipmap N, like previously.

GL_LINEAR_MIPMAP_LINEAR is also known as trilinear filtering.

Answer 2

i tried that function, but it didnt help at all, i wanted to change the angle when the miplevel changes, not the distance... is there some way to do this angle fix?

i wasnt sure which is the correct word so i used "lod bias" ... which was the only thing about miplevel changing i found