View Full Version : compositing shadows with background
07 July 2009, 06:58 AM
Hi all, I'm trying to integrate cg elements in a background movie, but I'm not satisfied by the results. The 'standard' way is to front project the background on the geometry, but this leads to weird colors wich I'm not able to adjust without heavily compromising the shadows. Then I thought to use alpha channel (shadow density) to drive the compositing in another software, but it appears that radiosity shadows don't go in the alpha (I use IBL).
I'm a bit surprised that there is no a working and supported solution (i.e. shadow catcher) available, as this is a very common scenario. How do you do that?
07 July 2009, 12:56 PM
There are several ways to do that. At surface level (Surface Node Editor) or at image level (Image Filter Node Editor). For a shadowcatcher solution (surface level), you may want to take a look at this thread in this same forum:
Besides many other things, Blochi has a clever solution for that.
07 July 2009, 01:09 PM
Thank you, I've seen that thread just after having sent my post :-) As soon as I go home I will try it.
07 July 2009, 04:53 PM
Hi, I was able to install Smart IBL, but I can't find where to find the shadow catcher: they say it is node based, but I never used nodes, so I don't know how to use it. Someone could help?
07 July 2009, 06:37 PM
Do take a look at the surface of the Ground object (Surface Node Editor). It's quite simple but very effective setup.
07 July 2009, 06:08 AM
Well, I did not see any Ground object :-( OK, first of, I must clarify that I'm not using HDR images for IBL, just a simple jpg. Can I use Smart IBL anyway? And how do I create that Ground object?
Sorry if I sound so dumb, but I'm not really a 3d artist...
07 July 2009, 04:07 PM
Have you installed the last .ibl update package?
According to the website:
2.0 Update Notice:
Most sets in this archive have been updated to sIBL v2.0. The HDR images haven't changed, but there is more info in the description files. Instead of downloading everything again, just grab this .ibl update package (http://www.hdrlabs.com/sibl/downloads/ibl_files.zip) and sort them into your sIBL-Collection.
The new info contains the new Ground object with its ShadowCatcher setup.
07 July 2009, 06:07 PM
Found :-) Now, I save the material setup, and import it on my own geometry: it seems to work fine at first, but it stops working as soon as I change some property (even on other materials). I should be able to figure it out alone though, thank you again!
07 July 2009, 03:16 AM
It would be good to know what not is working appropriately, since sIBL's ShadowCatcher could be improved to work in a wider range of possibilities. If you are not able to solve the trouble, you could report any bug or odd behavior here (http://www.hdrlabs.com/cgi-bin/forum/YaBB.pl?board=port).
07 July 2009, 03:16 AM
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