Does it look best/is normally used with or without mip mapping? I notice great improvements with both. -~-The Cow of Darkness-~-

Anisotropic filtering does not mean anything without mipmapping.

(thus, if you don''t setup your mipmaps, enabling anisotropic filtering won''t make any difference)

I notice definite reduction in the "flickeries" when I enable it, even without mipmapping. However, they go away entirely with mipmapping, and the "lines" are greatly reduced, but still there.

-~-The Cow of Darkness-~-

If you''re seing a difference between anisotropic nd isotropic filtering without mipmaps, there you''re experiencing precision problems into texture sampling, but there should not be a great difference, and maybe none at all.

The goal of anisotropic texture filtering is correcting the isotropic assumption of OpenGL''s mipmapping. Taken from the first lines of the spec :

quote:

---

Overview

Texture mapping using OpenGL''s existing mipmap texture filtering
modes assumes that the projection of the pixel filter footprint into
texture space is a square (ie, isotropic). In practice however, the
footprint may be long and narrow (ie, anisotropic). Consequently,
mipmap filtering severely blurs images on surfaces angled obliquely
away from the viewer.

---

What I read is that mipmapping artefacts incited to design the anisotropic texture filtering extension. So, by definition, there is no need to enable anisotropic when the texture has no mipmap.

Thanks... I''ll use it with mipmapping... however, I''m still trying to figure out why it looks so much better without mipmapping also... I''m using a geforce 2 GTS.

-~-The Cow of Darkness-~-

Your card doesn''t matter. It will look the same on GF2 and GF4 and Radeon etc.

It looks better if the polygon is almost tangent to the camera viewing direction because that''s when the isotropic filtering causes texture to blur. It looks better because it doesn''t blur... but when you''ll move (move either the camera or the polygon) it will flicker alot without mipmapping. With mipmaps it will blur but moving will not cause to flicker at all.

There is another extension that lets you control a level bias for mipmapping which allows to sharpen or blur textures without anisotropic (anisotropic is pretty texture-rate intensive and should be discarded if possible). This extension is EXT_texture_lod_bias or something like that.

could you please post some screenshots so that we can see what you mean by "anisotropic better even without mipmaps" ?

I don''t have an image host sadly, if I can I''ll post a link to a webpage or something. However, it does matter what card you have, because the have different maximum anisotropies.

-~-The Cow of Darkness-~-

You can email me the picture if you can't host it.
afair, my email is in my profile.

[edited by - vincoof on March 12, 2003 4:55:49 AM]

I'm going to necro this thread from several years ago . In the first image in this, notice that with only bilinear filtering the anisotropic version looks much better. I still don't know why though... I'll read that paper later, maybe it will help.

EDIT: Perhaps we shal never know...

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-~-The Cow of Darkness-~-

If you see the image I am online

Check out PGNet.tk

[edited by - cowsarenotevil on June 22, 2003 3:04:27 PM]