Re: Is this a texture paging problem?

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Allan Schaffer (allan)
Sun, 8 Jun 1997 16:34:54 -0700

On Jun 5, 5:48pm, Thom DeCarlo wrote:
> PF Loading texture:
> PF File name = .../cib.int
> PF Image size (SxTxR) = 2048x2048x1
> PF Download size = 16777216 bytes
> PF Download time =1314.261 ms
> PF Download rate = 12.174 MB/sec
> PF Total texture use = 16.000 MB
> PF This texture uses = 100.000% of 16MB memory
> PF Total texture use = 100.000% of 16MB memory
>
> So now the question becomes, why is a 4MB image file taking up 16MB of
> texture memory? Is it because my grayscale image is being duplicated in
> the red, green, blue, and alpha bands? If so, I guess cutting it down in
> smaller chunks will help.

The routine 'pfuGetTexSize' in libpfutil/tex.c is calculating that
this texture uses 4 bytes (32 bits) per texel. It does this
calculation depending on the PFTEX_INTERNAL_FORMAT.

So I'd guess this texture has an internal format of PFTEX_IA_12. You
should be able to modify this in your modeller. Change it to the
equivalent of PFTEX_I_8.

On RE and IR, textures are stored internally with either 16, 32, or
48 bits per texel.[*] If your texture is smaller than these you can
specify various packing styles via the pfTexEnv.

Allan
[*] According the code there seems to also be a format PFTEX_RGB_12
    which uses 4.5 bytes per pixel, which I was not aware]

-- 
Allan Schaffer                                                allan++at++sgi.com
Silicon Graphics                               http://reality.sgi.com/allan
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