I just downloaded the latest version of MegaPOV and played with
image_map filters : The filter on the first indexed color does not work
(ie : filter 0,1 does not erase the first color in the color index ).
I tried with a GIF and an IFF image.


This may be a known bug in MegaPOV but I did not find any list about it.

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Palette index 0 is typically black, or rgb 0 in POV terms, which can't be
filtered.
However it should transmit okay.  How about testing that?

Bob


news:392310E1.6EF45277@club-internet.fr...
| image_map filters : The filter on the first indexed color does not work
| (ie : filter 0,1 does not erase the first color in the color index ).
| I tried with a GIF and an IFF image.
|
| This may be a known bug in MegaPOV but I did not find any list about it.

Post a reply to this message

Well I use Paint Shop Pro to edit the color and the first one is 0.
Besides I rendered the scene with the official POV and it works as expected (
the first color is filtered).






> Palette index 0 is typically black, or rgb 0 in POV terms, which can't be
> filtered.
> However it should transmit okay.  How about testing that?
>
> Bob
>

> news:392310E1.6EF45277@club-internet.fr...
> | image_map filters : The filter on the first indexed color does not work
> | (ie : filter 0,1 does not erase the first color in the color index ).
> | I tried with a GIF and an IFF image.
> |
> | This may be a known bug in MegaPOV but I did not find any list about it.

Post a reply to this message

I checked this out myself now and I saw both Windows versions
(official/unofficial) do the same.
If palette index 0 is other than black (rgb 0) then it's as expected and
filters the color.
So, I'm not able to verify what you saw wrong in MegaPov 0.5.

Bob


news:392320A2.97D90D96@club-internet.fr...
| Well I use Paint Shop Pro to edit the color and the first one is 0.
| Besides I rendered the scene with the official POV and it works as expected
(
| the first color is filtered).

Post a reply to this message

> I just downloaded the latest version of MegaPOV and played with
> image_map filters : The filter on the first indexed color does not work
> (ie : filter 0,1 does not erase the first color in the color index ).
> I tried with a GIF and an IFF image.
>
>
> This may be a known bug in MegaPOV but I did not find any list about it.
>

I just tested it on my system and it works.  Maybe PSP is re-arranging the
indices without telling you?  (It's done that to me before.)  Try using
transmit 0,1 also.

-Nathan

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I tried transmit instead of filter.....and it works.

I also opened and saved the images ( "p2.gif" and "p256.gif") using both
Gimp and Photoshop 5.0, but I still get the same result.

I made a greyscale image from scratch with Photoshop
:"samira.gif", but I still get the same result ( filter does not work,
transmit does).

I also tried the linux version of MegaPov 0.5 (just in case my
problem was inherent to the platform, you never know), but I
still.......you know the rest.

I enclosed a zip file with the test and images.

I may be doing something wrong but I just don't see what.


Cheers






> > I just downloaded the latest version of MegaPOV and played with
> > image_map filters : The filter on the first indexed color does not work
> > (ie : filter 0,1 does not erase the first color in the color index ).
> > I tried with a GIF and an IFF image.
> >
> >
> > This may be a known bug in MegaPOV but I did not find any list about it.
> >
>
> I just tested it on my system and it works.  Maybe PSP is re-arranging the
> indices without telling you?  (It's done that to me before.)  Try using
> transmit 0,1 also.
>
> -Nathan

Post a reply to this message

Attachments:
Download 'test.zip' (11 KB)

> I tried transmit instead of filter.....and it works.

Here's the deal:

Filter does not work because the texture is black.  If you use filter 1.0
with a black texture, no light will get through because filter works by
multiplying the transmitted light by the pigment color.  That way, if you
use filter 1.0 with a blue pigment, only blue light will get through.  If
you want all light to get through, use transmit.

HOWEVER, filter works differently in the official version because you're
using a layered texture.  In the official version, layered textures treat
filter as if it were transmit.  This, in my opinion, is not correct, so it
has been "fixed" in MegaPov.

In other words, the official version is incorrect, and MegaPov is correct.
You should use transmit 1.0 in this case.

-Nathan

Post a reply to this message

Thanks for the explanation.






> > I tried transmit instead of filter.....and it works.
>
> Here's the deal:
>
> Filter does not work because the texture is black.  If you use filter 1.0
> with a black texture, no light will get through because filter works by
> multiplying the transmitted light by the pigment color.  That way, if you
> use filter 1.0 with a blue pigment, only blue light will get through.  If
> you want all light to get through, use transmit.
>
> HOWEVER, filter works differently in the official version because you're
> using a layered texture.  In the official version, layered textures treat
> filter as if it were transmit.  This, in my opinion, is not correct, so it
> has been "fixed" in MegaPov.
>
> In other words, the official version is incorrect, and MegaPov is correct.
> You should use transmit 1.0 in this case.
>
> -Nathan

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I have always taken  for granted that the official version of POV is flawless.



> Thanks for the explanation.
>

>

>

> > > I tried transmit instead of filter.....and it works.
> >
> > Here's the deal:
> >
> > Filter does not work because the texture is black.  If you use filter 1.0
> > with a black texture, no light will get through because filter works by
> > multiplying the transmitted light by the pigment color.  That way, if you
> > use filter 1.0 with a blue pigment, only blue light will get through.  If
> > you want all light to get through, use transmit.
> >
> > HOWEVER, filter works differently in the official version because you're
> > using a layered texture.  In the official version, layered textures treat
> > filter as if it were transmit.  This, in my opinion, is not correct, so it
> > has been "fixed" in MegaPov.
> >
> > In other words, the official version is incorrect, and MegaPov is correct.
> > You should use transmit 1.0 in this case.
> >
> > -Nathan

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> 
> I have always taken  for granted that the official version of POV is flawless.

A dangerous assumption :)

  Anyway the behavior of layered textures is a matter of interpertation
rather than a flaw. Some argue that the way the official version works
is the correct behavior while others, like Nathan, argue that his version
is the correct behavior.

-- 
Ken Tyler - 1400+ POV-Ray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html http://www.povray.org/links/

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