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Casting shadows without the object being visible
Posted: 16 August 2012 03:58 AM   [ Ignore ]
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Hi,

I need my object to cast shadows, but I don’t want it to appear in the rendered picture (as if it was completely transparent).
Can this be done?

Thanks.

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Posted: 16 August 2012 04:20 AM   [ Ignore ]   [ # 1 ]
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Not sure

but Fenrik has a “toward/away’ shader with which you can have different shaders on either side of a polygon. I guess you could make one side transparent?
Put it in the alpha chanel and then invert.
Maybe not,
http://www.daz3d.com/shop/pose-and-shading-tools-2


Also Inagoni has baker which will bake shadows onto a texture and let you export it - so the shadow will still be there even if object casting said shadow is not.

http://www.inagoni.com/e107_plugins/content/content.php?content.3


you can also put texture maps on lights
so with some fiddling you could get the shadow on the texture map and project it

also carrara has negative lights which with fiddling could emulate a shadow

just depends what its the shadow of I guess

 

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Posted: 16 August 2012 04:57 AM   [ Ignore ]   [ # 2 ]
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I think maybe you’re talking about a shadow catcher?

Maybe if you describe a bit more what you’re trying to do…cause it’s not real clear what result you want to get. You can remove objects from your render in post (using an “object index” pass), leaving only their shadows, but I’m guessing that might not be what you really want.

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Posted: 16 August 2012 05:41 AM   [ Ignore ]   [ # 3 ]
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If you are using a distant light, you could just move the object out of the field of view, and the shadow will stay the same size.

But as has been said, you perhaps need to describe what you want to achieve in more detail, including what lighting you have in your scene.

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Posted: 16 August 2012 05:55 AM   [ Ignore ]   [ # 4 ]
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Hello Eyos!

That´s an easy one:
Just apply a black color / 0% to the Alpha-Channel to your “ghost”-object and
put off “Light through Transparency” in the Rendering-Room-Tab.
Voilá!

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tezen

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Posted: 16 August 2012 05:59 AM   [ Ignore ]   [ # 5 ]
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Heh, heh
Live and learn eh? Nice idea tezen

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Posted: 16 August 2012 06:07 AM   [ Ignore ]   [ # 6 ]
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Hey Headwax!
Live&Learn;? Sometimes… but mainly I`m waiting for earned money. Until that I`ll relax :D !
Greetings tezen

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Posted: 16 August 2012 06:36 AM   [ Ignore ]   [ # 7 ]
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tezen - 16 August 2012 05:55 AM

Hello Eyos!

That´s an easy one:
Just apply a black color / 0% to the Alpha-Channel to your “ghost”-object and
put off “Light through Transparency” in the Rendering-Room-Tab.
Voilá!

Greetings
tezen

OK provided there is no other transparency in your scene.

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Posted: 16 August 2012 07:00 AM   [ Ignore ]   [ # 8 ]
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@PhilW: Of course! ...but with some compositing-work even that is possible.

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Posted: 16 August 2012 08:06 AM   [ Ignore ]   [ # 9 ]
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Very true!

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Posted: 16 August 2012 11:16 AM   [ Ignore ]   [ # 10 ]
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I appreciate all the ideas and suggestions. Thank you very much everybody.
Eyos

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Posted: 16 August 2012 05:32 PM   [ Ignore ]   [ # 11 ]
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tezen - 16 August 2012 07:00 AM

@PhilW: Of course! ...but with some compositing-work even that is possible.

ANYTHING is possible with some compositing work, but “fixing it in post” shouldn’t be the goal. I’m still curious about the original intent. Something isn’t quite adding up. I just hope he’s not going roundabout for something he doesn’t need to go roundabout on.

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Posted: 16 August 2012 08:28 PM   [ Ignore ]   [ # 12 ]
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JoeMamma2000 - 16 August 2012 04:57 AM

I think maybe you’re talking about a shadow catcher?

Maybe if you describe a bit more what you’re trying to do…cause it’s not real clear what result you want to get. You can remove objects from your render in post (using an “object index” pass), leaving only their shadows, but I’m guessing that might not be what you really want.


I agree, more information about the scene would help.  I was thinking a shadow catcher as well, but they can also act as a mask. If there’s an object in the scene that’s behind it, or partially obscured by it, then it would be masked by it. Strangely, I used one once and mistakenly intersected the shadow catcher with a model (I was using it to mask the model I wanted it to appear later in an animation), and the model behind it was completely visible. Of course the alphas in the shader on the object may have confused Carrara as well.

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I find it somewhat liberating not to be encumbered by accuracy.

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