Background Plate Render

[Bruce Hart]

Hey
Very occasionally I need to montage a building on a background image. 99% of the time this is just a simple comp in photoshop as usual. Say however you wanted an exact background image to be reflected in the scene geometry (poolwater, shiny floors etc). If I put the backplate bitmap in the background as a screen environment with a GI override for the skylight - I get the result attached:


The teapot has a simple white material with no refraction or opacity, and yet you can see the background through it in the shadow areas. Why is this? I can kind of understand how the reflection of the background bitmap on the blue plane would not work, as it is an arbitrary flat screen environment. Is there a way of achieving this without putting the backplate on a literal plane in the scene? BTW the blue water plane in this image has no refraction turned on either, and yet the background shows through it.

Cheers

[mitviz]

it think the solution someone had given me was to just turn on environment and reflection in vray environment and turn colors to black, try that

[svetlozar.draganov]

This is usually caused by the GI when environment map is added in screen-space.
Change the mapping of the GI environment map to spherical and it should render fine.

[mitviz]

but sometimes you want it in screen-space

[svetlozar.draganov]

GI environment with screen space will always project the image over the geometry.
And under what circumstances is it necessary to add GI-environment in screen-space? You may add the background image in screen-space that's fine but adding the same image in GI-environment will cause those defects since GI requires other mappings types in order to generate more accurate result.