I need to composite a 3D object rendered with the light tracer
on a 2d background.
Seems Easy ... but !
here is the scene:
A ground and a wall are matte/shadow.
with just a skylight.
If I render this object on white, its perfect.
But I need black bg for compositing reasons.
If I render it on black, the shadow are grey
and in the rgb channel !!!
So, when I composite on top of the 2D bg,
I get those grey shadows over the bg!!
Of course I can handle this in a compositing software,
with some tricks using the alpha of the object only...
But, I apply some filters in compositing so with this trick,
I got lots of bugs due to alpha outlines... if u see what I mean.
Actually it seems that the matte/shadow material doesn't
work with the light tracer....
I check the adv. Lighting properties (cast shadows and receive illum) but it doesn't really help the problem.
A way boring way to solve this would be to be able to cast the shadows without rendering the object, but I'm just enable to do that. Before I used a blur material made for that, but it just work with raytraced shadows. The matte/shadows can't really do that cause it just "erase" everything inside the object alpha.
Maybe its a bad idea to use the light tracer for a indoor scene?
Maybe I should use radiosity ? (I never really try this) (seems very technical)
Whaouh! I just read my msg ... its not very clear !!!
I hope someone will understand all this !!!
Even BETTER !! I hope someone already got this pb and have a good solution ...
let's hope ...
To sum up all this, I have 2 questions :
1- is there a way to get the light tracer rendering with all the shadows in the alpha channel only ???
2- Is there a better way to make this VERY SIMPLE composition?
with a rendering quality at least as good as the light tracer.
lookin for any hints, help, tricks ... PLiiizzz