Hi, I got a setup where the camera looks through a window with roughness texture on to an object (see picture). Right now I got a background image added in the camera and in the compositing node tree.
Later on I think I want to just get an alpha channel and add the image my self in Photoshop.
But as soon as I render with the glass in front of the camera blender can’t, for obvious reasons, render out an alpha channel or comp in the background image in the compositor.
Is there a way to solve this? I really would like to get the smudge and scratches of the glass material rendered out and still get an alpha.
/Thanks
The basic answer is no - even if you could do this, the the roughness will not be included in the image, and so that roughness map blurring the background image would not be included.
The easyist solution would be to add a plane with your background image on it behind everything else in the scene. Make it shadeless - use U > project from view (while viewing through the camera) to map the image to the view exactly.
Nice! Thanks, I’ll try that.