View Full Version : GL_SGIX_generate_mipmaps

04-20-2002, 01:37 AM
well then, dave once again..

i'm just playing around on blurring images, and, as the way with the multiple smaller images and drawing recursively the previous tex on the smaller only worked on my gpu and one other, i gave it up (difficult to find the bug then.. http://www.opengl.org/discussion_boards/ubb/smile.gif)
so i looked for some new ways, means using the mipmap-layers of the texture. now as first try i thought, to find out if i get GL_EXT_texture_lod_bias working correctly, u use GL_SGIX_generate_mipmaps to do the job for me.. and well, it works, i can directly choose and draw one layer of the mipmap..

just one problem: the mipmaps are crap. why? cause they are generated as crap. namely with nearest filtering they generate the downsamples..

the result (drawn with nearest filtering to see it bether) looks like this: http://tyrannen.starcraft3d.net/nearestfilteringofGL_SGIX_generate_mipmapsongeforc e2mx.jpg
and as you can see, it gets all "shifted down", means on the right, the blue triangle gets much bigger in the lower lods, and the orange one gets smaller and smaller..

thats not useful for blurring the screen. (the blue triangle gets much bigger blurred than the orange one, but they are of the same size..)

how can i get other filtering-methods with generate_mipmaps? or do i have to do it myself? thats no problem, i can do that (and hope it runs on other hardware as well this time http://www.opengl.org/discussion_boards/ubb/wink.gif)

04-20-2002, 03:45 AM


[This message has been edited by R-C (edited 04-20-2002).]

04-20-2002, 10:15 AM
don't see a difference (yet) i'll play around with it.. any statements from nvidia-guys how the mipmaps are generated for render_texture's on geforce2? and, if the hint helps at all?

04-20-2002, 12:09 PM
This is a bug I fixed a while back. If you get recent enough 28.xx drivers they should include the fix.

- Matt

04-20-2002, 12:25 PM
i have the newest from nvidia.com... well.. i'll download them again and installem http://www.opengl.org/discussion_boards/ubb/wink.gif

04-20-2002, 01:07 PM
May not be on our web site, not sure.

- Matt

04-20-2002, 01:54 PM
well.. its 28.32_winxp.exe
new enough?

04-20-2002, 05:31 PM
I doubt that'll have the fix.

- Matt

04-21-2002, 01:23 AM
now using 28.80. no difference.. and i set the hint in every renderingcontext (dunno if this is needed, but for making sure its not me http://www.opengl.org/discussion_boards/ubb/wink.gif)

not to use like that.. annoying..
think i'll stick back to the old version, there the driver bug was not on my gpu but on everyone's else (so at least i can see the blur correctly http://www.opengl.org/discussion_boards/ubb/wink.gif)