An integration of 3d object into the photo.

[Saramary]

Hi everybody!
I need to create an integration of 3d object (building) into the photo of real exterior.
I planned to do the render of building with a plane for shadows with alpha-channel. After that I will made another render without plane and use this render like a mask in Photoshop. But in this case I am getting a non-realistic result with "floating" bilding, because there is no dark stripe between a real asphalt and 3d building. The question is: how to combine the plane for shadows with full picture to get a photo-realistic viz.

Sorry for my English.

[roeland]

You can try the following:
Create a ground plane of roughly the same color (or with a similar texture) as the asphalt, and render the object on this ground plane.
then make a render of only the ground plane without the object.

When compositing on the background image, substract the render of only the ground plane, and add the render with the object. The mask for these operations should be the parts of the image where the ground plane that is visible (i.e. the alpha mask of the plane minus the alpha mask of the object).
Then composit the render with the object your object using the alpha mask of the object.

--
Roeland

[Saramary]

Roeland, thanks for advice! I'll try your method, but I think that something like matte/shadows material will be the best decision in this situation.

[mbetke]

I think there is None. Couldnt you just use mentalray with Matte/shadow for the ground and compose it with the octane rendered picture?