ATi: fragment programs expose wrong light position?

OpenGL OpenGL: Advanced Coding
1

this sounds extremely weird to me but, believe it or not, i’m getting light positions in world space on ati boards when using arb_fragment_program and asking for state.light[x].position

i always thought light vectors were transformed by the current mv matrix when calling a glLightfv command, and actually this is what i get on nv boards in the same test application

vertex programs are working fine instead (returns eye space position)

can anyone confirm this?

oh btw i am using the latest omega drivers, based on CATALYST 5.1 Driver Build 6.14.10.6505

thanks for any help you may provide

2

this is something i ran into a few weeks ago as well… but not only that state.light[x].position seems to be wrong within an arb_fp (and correct in an arb_vp) also the modelview matrix in a fragment program seems not to be correct…
i tested this by writing a vertex program that was passing one row of the modelview matrix as color and comparing the results to a fp that did the same… in the fp the modelviewmatrix seemed to be the inverse of the true modelviewmatrix.

3

sheez, you are definitely right, i’ve been trying to output row[0] of texmatrix[0], and ati fps actually output column 0, while vps output row 0

is this the way it’s meant to be?!?

on the other side, nv boards show coherent behaviour between vps and fps

4

This is one of multiple fragment program bugs that I reported to ATI months ago. If it isn’t fixed by now I don’t expect it to ever be fixed. That’s why I have an NVidia card now :slight_smile:

5
  • ouch *
    that hurts
6

Yes, that may have been a bit harsh. I’ll start a flame war if I’m not careful :stuck_out_tongue: I guess I also switched because I got tired of waiting for GLSL support under Linux. I almost never use arb_vp and arb_fp anymore; GLSL is too much fun.

7

so, is there any chance this could be fixed in the near future? how do i report this to ati driver team?

8

devrel@ati.com

I’ve found that they listen better if you include a program that is easy to run to see the problem; ideally in source.

9

thanks for your reply
i have already sent em an email saying i may provide some test app if needed
but i think they should definitely be aware of it judging by the gravity of the problem and by the number of people experiencing it