Re: Artifacts with very large texture coordinates

[Keith W. <ke...@tu...>]

Felix K=FChling wrote:
> Hi,
>=20
> I noticed some strange rendering artifacts with the Savage that are
> caused by very large texture coordinates on GL_REPEAT'ed textures. Very
> large means that it gets noticeable with texture coordinates >255 or
> <-256. A real world example that exhibits this problem is Torcs with th=
e
> "Spring" track. Right at the start the effect can be seen very nicely.
> The track before the start line shows artifacts, directly after the
> start line everything looks fine.
>=20
> My question is, should I consider such problems an application bug or
> would it be wise to implement a workaround? I was thinking of
> implementing a TNL pipeline stage that normalizes texture coordinates.
>=20
> I was also wondering if other hardware has similar problems. I'm
> attaching a small test program that demonstrates the effect and a
> screenshot of what I get on my ProSavageDDR. With software rendering th=
e
> output is almost correct. Compile with=20
>=20

The mesa software rasterizer and a number of the hardware devices start g=
iving=20
odd looking results for very large texture coordinates.  In the past we'v=
e=20
treated it as an application issue and fixed the demos causing the proble=
m.

If you the app takes things to extremes and start sending enormous texcoo=
rds,=20
there's nothing we can do about it because there aren't enough bits left =
in a=20
float to represent the fractional part of the coordinate.  So at a certai=
n=20
point it has to be an application bug.

Keith