Re: Problems with fading alphatexture in .flt

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Rob Jenkins (robj++at++sgi.com)
Tue, 01 Dec 1998 03:32:37 -0800

Jonas Andersson wrote:
>
> Hi pfAll,
>
> With Multigen I have created a square with a texture that is
> smoothly fading from black to transparent.
>
> When loading it with perfly however, it looks like each pixel of the
> texture is fading "in the opposite direction" of the fading texture.
>
> The result is vertical stripes, each stripe being more transparent than
> itīs left neighbor, but each stripe being more transparent to the
> left than to the right.
>

Hi

Your texture has alpha decreasing left->right so you'd expect to see
transparency increasing left->right ( alpha is the inverse of
transparency ). ( You can look at this in imgview, get the magnifier
window up and move along your texture to see alpha decreasing ). If you
get imgview ( or any other tool ) to flip your texture horizontally then
in perfly the transparency decreases left->right.

The banding will be down to performer's internal texture storage, from
man pftexture:

...
pfTexture::setFormat
...
PFTEX_I_12A_4 16-bit texels. The default 2 component
internal format.

So you need to force performer to use more bits to store the I_A info
you have with say PFTEX_IA_12

Cheers
Rob

> It seems to me there are some kind of property I could use to fix this
> problem, but I donīt know which. If you know, please let me know...
>
> Example files are attached in fadetest.tar.
>
> Thankīs in advance for any help.
>
> -- Jonas
> ________________________________________________________________________________
> Jonas Andersson jonasa++at++acc.umu.se, http://www.cs.umu.se/~jonasa
>
> ------------------------------------------------------------------------
>
> Name: fadetest.tar
> fadetest.tar Type: Unix Tape Archive (APPLICATION/x-tar)
> Encoding: BASE64

-- 
________________________________________________________________
Rob Jenkins	Silicon Graphics 	mailto:robj++at++sgi.com

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