Need help with depth compositing in Nuke

[exyide]

Hi what im trying to do is composite a sign into a grass field. I have both images as open exr and have my beauty pass, AO, depth and others. When I comp them together with an over or matte it simply puts the sign over all the grass. What I need to do is make it look real by having some of the grass in front of the sign and some of it behind like it real life. Any ideas on how to do this in nuke? What I want the end result to look like is the photo below but I cant get the sign to look like its in the grass. I cant figure it out, any help would be great. Thanks.

http://www.flickr.com/photos/[email protected]/6395302497/

[Niccolò]

Hi,
Well you could do it in couple of ways.
1. since you did render z buffer you can use that to generate cut mask for grass.
For instance you can do this by using Keyer with depth as input and use range sliders to pick depth and then use that alpha to cut poles at that depth.

2. render a small patch of grass from front or side view (just grass patch nothing else) and use that alpha (blades of grass) as a cut for poles of your sign. Depending on your grass type that can be used over and over again. Even do its not technically correct its very effective.

Cheers,
Kristijan

[Anonymous]

Thanks for the help, im very new to nuke but have some compositing experience with both shake and after effects. Are there any tutorials or videos that go over how to do either of those methods in nuke? Thanks.

[Author]

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