I have gone a bit post crazy however I am putting together a short film and have hit a few stumbling blocks I was not expecting.
The biggest one at the moment is this one.
I have a billboard texture (2d animation with alpha) that interacts with the environment - ‘walking’ in front and behind objects.
I however wish the landscape (3d model) to have a defocus node - but I want the 2d animation to always be in focus (distance from camera will change little but I don’t want any fuzziness)
So I split the 2d animation and the 3d model onto two render layers and I used the Alpha over option to combine them, which worked great except that the 2d animation always appears ‘above’ the 3d environment. So I tried just the z-combine node however no alpha is carried over, so the billboard is solid.
So I applied the 2x z-combine + mapping negative values + alpha over nodes as per wiki Manual-Node-ZCombine_ex_alpha but the alpha over seems to leave behind traces of the alpha on the 2d animation billboard, i.e it is not 100% see through. Its like it tried but could not quite do it.
I do not understand why this is.
here is one with just the alpha over (works fine but no z depth cant move behind trees ‘walk’ into the distance etc.)
here is same frame same portion with 2x z-combine + alpha +map value thing
Nothing else has been changed in the scene. you see it leaves the outline and has the billboard almost transparent.