Combining CG Vray with Photo: Please Help!

[elitesouljah]

Hello All,

For a school project, i am taking my first shot at putting cg objects in photos seamlessly. So far, I think I am on the right track. I first took a photo of my environment, and then roughly replicated the environment in 3d to get proper shadows, etc... However, I now need to find out how to transfer the shadow my 3d object makes (the speaker) in the replicated scene to the real one. Here are some photos to show you what I am talking about. I am using Vray, so I will understand any instructions you give me!

I really appreciate the help, and any other suggestions you all have on combining cg and photos!

Test Renders:
http://home.comcast.net/~elitesouljah/real_life.jpg
http://home.comcast.net/~elitesouljah/room_replica.jpg

[sea2stars]

To get the shadows you'll need to setup the CG desktop as a matte object, under the Vray object properties of the desk, and use your photo ask a background.

[instinct]

To be more precise :
In the VRay Properties of the environment objects:
Turn on Matte object. Set Alpha Contribution to -1
And right below turn on shadows and affect alpha.
Then add the background as a normal background and you're done

Regards,
Thorsten

P.S. If you want proper reflections (and on a speaker you do i'd guess :P ) You'd
either need to recreate the environment in a bit more detail and textured or aquire a Spherical HDR of the Room.

Regards,
Thorsten

[elitesouljah]

Thank you very much, I will try that.

I would appreciate any other suggestions on how to best pull off this effect.

[priad]

and don't forget to right clic on the matte, object properties, don't cast shadows because if you don't do that you will have all the shadows and not just the needed one.

[elitesouljah]

First Test

Hello All,

Thanks for your help with this topic. Here is a test render in which the speaker casts shadows on the table and has reflections via an hdr image. It's starting to look pretty convincing, but I would appreciate some critique and comments about how I can make it better.

Thanks,

Phil

My Test Render:
http://home.comcast.net/~elitesouljah/real_life2.jpg

[RErender]

You can try camera projecting your background image onto the desk matte to get the right color bounce under the speaker.

[elitesouljah]

How exactly do you do this? Step by step would be helpful - I'm still a beginner

[instinct]

You add a cameramap modifier to the matte geometry. Select your view camera as input camera. Then add the original photograph as diffuse map to the material and you're basically done. Mind you that you need a pretty high tesselated mesh for the standard cam mapping to work distortionless.

Kind Regards,
Thorsten

[victor.nsy]

Hype,

working with cg object just gives you the sharp edges sometimes.
It give way to which of the object are real and which aren't ...
Play ard with lens blur in photoshop maybe for the cg object.
Don't really know how you can do it but I would try and render a
zdepth and an alpha for compositing in CS3...

give the specular just a tiny bit of blooming effect would do some
magic too ... as you observe some blooming effect on the laptop and
surrounding objects.

shadow color is just a little bit off too. a slidely warmer tone would
do the trick.

best regards,