a. there is a halo on the borders between shadows from normal pass and matte pass
b. the shadows on matte objects in the matt pass are slightly darker then the shadows in the normal pass
There is no GI turned on in the scene, just one direct light and 3 fill lights.
I know one solution would be to render NO shadows in the normal pass and render ALL shadows (NO GI on other mattes unchecked) in the matte pass, but I am just wondering if there is any other way to get rid of those compositing errors.
The bright edges are an issue that often gets people and I’ve had to explain it time and time again… it is not related to V-Ray, but is a general compositing problem and the solution boils down to this: do not multiply anti-aliased elements/layers which have high-contrast transitions along the same edges. In this case, for example, the bright edge on the greenish box in the normal pass, and the shadow boundary along the same edge in the matte alpha pass.
The reason is that because of antialiasing, the light is diffused along the edge boundary, leaking into areas which wouldn’t be illuminated in a regular rendering.
One way to reduce the effect is to render and composite in higher resolution, and then scale down the result.
The reason is that because of antialiasing, the light is diffused along the edge boundary, leaking into areas which wouldn’t be illuminated in a regular rendering.
Thank you Vlado for a quick response.
It is clear to me now why I am getting the halo on the edges but that still does not explain the darker shadows in the matte pass.
Any ideas ?
It is a simple two layer compostition in Combustion, each image rendered and saved as PNG with an alpha channel.
It looks the same in Photoshop too :(.
It was my fault, those boxes had no material assigned using just plain max wireframe colors.
As soon as I assigned either standard or vray materials, the shadows got consistent.
