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Hello !
I'm currently trying to generate a POV image with transparent background to
paste it on a real life photo. I would like to render the shadow in alpha
channel on an invisible table (which have the 'no-image' flag on), but
nothing appears at all... Is there a way to do this ?
Thanks
---
Hombre
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Hombre wrote:
> Hello !
>
> I'm currently trying to generate a POV image with transparent background to
> paste it on a real life photo. I would like to render the shadow in alpha
> channel on an invisible table (which have the 'no-image' flag on), but
> nothing appears at all... Is there a way to do this ?
Not that easy. You can render the alpha channel in a second render
(with the table in white color and the object that casts the shadow in
black. Then you can use this (grayscale) image as the alpha channel in
the image (for example using Imagemagick).
Christoph
--
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 23 Sep. 2004 _____./\/^>_*_<^\/\.______
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Wasn't it Hombre who wrote:
>Hello !
>
>I'm currently trying to generate a POV image with transparent background to
>paste it on a real life photo. I would like to render the shadow in alpha
>channel on an invisible table (which have the 'no-image' flag on), but
>nothing appears at all... Is there a way to do this ?
You can't do it in one pass. See my web page for info on how to do it in
two passes.
<http://www.econym.demon.co.uk/shadowtut/index.htm>
--
Mike Williams
Gentleman of Leisure
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Thanks for the reply, i didn't tought about those solutions (and didn't
thougt that it was possible).
I think i will manage to do my picture now :-) !
Thanks
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I've done my picture.
If you want to look at it, just look at
http://natureh.free.fr/mirror/Img1-Demi-final.jpg (or
http://realitydesign.asn.org.uk/index.php?page=media, where you can find
other picture and animations rendered with POV-Ray 3.6)
This pictures and anims has Copyright, and free use is not permited.
We see rather well the 'trick', but le goal is not to have something perfect
(not enough time), but not that unreal too.
It had been rather tricky to obtain this result... I had to generate a
render with transparent background ("Output_alpha = on"), without table nor
wall, and a rendering with only the shadow that interest me ; "Output_alpha
= off", white background, white wall and table, the other objects are
'flagued' as 'no_image' (they are not rendered, but theire cast shadows are
!) -> the result is used as masking chanel in the photo retouch software
that do the compositing (real life photo as background, dark grey with alpha
chanel follow, then the objects rendering with it's own alpha chanel).
---
Hombre
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