#400 R128 specular normals scaling error

Rendering Error
open
nobody
ATI OpenGL (71)
5
2002-02-03
2002-02-03
Joesph Krahn
No

Rage128 is handling specular normals badly in some
cases. When zooming out in the crystallography program
"O", specular highlights get saturated, as if all
normals are being inversley scaled. This does not
happen with indirect rendering.

I am attaching an image illustrating the problem. On
the left are three images clipped from R128 DRI, with
zoom close, middle and far. On the right is one image
with LIBGL_ALWAYS_INDIRECT=1.

I don't have the source, so I don't know the details
and cannot readily make a simple demo app. Maybe for
someone who knows Mesa/R128 differences can figure this
out quivkly. The program uses orthographic projections,
and keeps the W part of the matrix 1.

I will try to make a simple demo app, and will test it
on a Radeon card. Also, this bug has been there for a
long time.

P.S. R128 gets fog correct with line objects in
orthographic projections. Mesa used to, but now is
broken again.

Discussion

  • Joesph Krahn
    Joesph Krahn
    2002-02-03

    Clips of 4 R128-DRI scenes (left), and one Mesa scene (right).

     
  • Joesph Krahn
    Joesph Krahn
    2002-02-03

    Logged In: YES
    user_id=76454

    I've been trying to make a little test app to reproduce the
    bug. with no success. However, I did find that other normals
    are mis-scaled as well. It looks like the a problem with
    GL_NORMALIZE being broken, but only for certain
    circumstances.

     
  • Joesph Krahn
    Joesph Krahn
    2002-02-09

    Logged In: YES
    user_id=76454

    This bug may be why tuxracer penguin is washed out to white
    with R128 DRI.