From: Angus Dorbie (dorbie++at++sgi.com)
Date: 03/26/2001 22:01:39
It is possible to figure this out from first principals.
TRAM is split into two banks for MIP mapping, alternate levels of MIP
are stored in opposite banks. This means that a 32 MB bank is available
for storing level 0, 2, 4, 6, 8 etc. The other 32 MB bank stores level
1, 3, 5, 7 etc.
The other info you need is that a texel must be stored in multiples of 2
bytes, this is the word size of TRAM memory. This means that an RGB 555
image texel will occupy 2 bytes and an RGB 888 texel will occupy 4 bytes
(not 3 as you otherwise might assume).
So, a 4k by 4k image will be 16777216 texels or 33554432 bytes or 32 MB
if the internal format is RGB 555, it will therefore NOT fit in TRAM if
MIP mapped because there will be no space in the bank for level 2 once
level 0 is loaded. If you do not MIP map it it will fit, and infact I
think an 8k by 4k non MIP mapped image would be possible.
A 4k by 2k RGB 555 MIP mapped texture would be possible. The largest
square MIP mapped RGB 555 texture would be 2k x 2k.
If you need larger images the latest RM's have more TRAM (256 MB) and
can therefore support larger MIP mapped images without using
cliptexture.
Cheers,Angus.
"Mercier, David A" wrote:
>
> Is a mip-mapped, 4K x 4K RGB texture the largest square, power of 2, image
> you can load into a 64mb IR2 graphics pipe (without going to a
> clip-texture)?
>
> David Mercier
> Naval Air Warfare Center - Weapons Division
> Code 471100D
> China Lake, CA 93555-6100
> 760-939-7251, DSN 437-7251
> FAX 760-939-6893
>
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