Re: Incorrect Texture Mapping on Reality Engine 2
Marcus Barnes (marcus++at++multigen.com)
Mon, 2 Oct 1995 15:02:24 -0700
On Oct 2, 2:28pm, Hansong Zhang wrote:
> Subject: Incorrect Texture Mapping on Reality Engine 2
> Hello everybody,
>
> I had a strange problem when displaying a model (MultiGen .flt file)
> on an Onyx with Reality Engine 2 graphics, using Perfjoy or Perfly.
> On the texture mapped walls there're visible color bands, but the
> texture map is greyscale (though I can't say the rgb values are
> the same for any pixel). For some faces the mapping is largely
> correct but with color bands, for others the color is not correct
> at all.
>
> I'm using very small textures (e.g. 16x16). I tried to display
> the same model with the same software on an Indy (with no hardware
> texture support) and the result is correct. I mapped the texuture
> to a square using OpenGL and it works O.K. So the problem should
> be somewhere between Perfly and the graphics hardware.
>
> Any suggestion will be appeciated!
>
> Hansong
>
>
> Hansong Zhang
> Grad student
> UNC-Chapel Hill
>-- End of excerpt from Hansong Zhang
This sounds like the IRIX 5.3 texture repeat bug on Reality Engine.
Basically, texture repeat counts greater than 4 bits (15) would smear
badly. I believe there's a Patch for it now. I don't know the
number though. Sharon Clay diagnosed this bug for me months ago.
Sharon explained that exceeding 4 bits of repeat invokes an exception
in the RE microcode ... that is broken in IRIX 5.3. Also, even with
the patch, this condition draws slower.
--
Regards,
Marcus Barnes, Member Technical Staff
MultiGen Inc, 550 S. Winchester Blvd. STE 500, San Jose CA 95128
PH: 1-408-556-2654 FX: 1-408-261-4102
EMAIL: marcus++at++engr.multigen.com
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on Mon Aug 10 1998 - 17:51:56 PDT