Hi
I’m doing a animation of a card that shall be imported to Flash with PNG’s. The background needs to be a vectorgradient so the plane where the card stands have to be transparent in the PNG file.
The obvious solution would be to use a matte material on the plane where the card stands, but in addition to the shadow, I want the floor reflecton to show up in the PNG. How do I do that?
The image below shows what I want to do… The green areas need to be transparent…
Thanks from Chris
as far as I know the reflection does not effect the alpha channel. not sure if this is an option for you but if you render it over green like in your image you could always key it in after effect and save out the png sequence from there. I’m not sure how clean it would be but it would give you an alpha of the reflection.
I’m sure other people will have suggestions for this one.
V Miller
Yep currently reflections on mattes are not implemented.
Has been mentioned a few times before.
Should work to make your environment white and you object black, then just invert and use as the alpha of a regular pass.
RErender: Good idea, but how can I get the plane 100% white without “overexposing” the reflections and shadow? any other way than turning up the lights?
vance3d: hmm… could do it on a bluescreen, but I think it will be a bit “dirty” in the quality 
Any other solutions besides matte object?
- Chris
I guess you could always just run 2 passes if its quick to render.
One to get your wanted alha and one to get the reflection channel.
You could black and white reflection pass then stick it and the alpha together in PS and use that as the alpha on the normal RGB render?
Probabaly wouldnt be all that accurate tho.. but might work.
Or what RErender said would work pretty well too I think.
RErender: umm… could you give me a hint on the setup of the matte material? 
I have problems getting the plane 100% white even with the matte material
EDIT: Found the problem… Color Mapping was set to Exponental and not Linear Multiply… Now it works… Thanks!!
The settings I use on the matte material:
Will this feature be available in RC4?
I dont think so.. but then again, I havnt heard specifically either way.
I think if you are going to go down the path of making a matte reflection you might want your full color version to have a reflection that is at 100%.
If you don’t you will double up on the amount your reflection is being blended with the background and it will become weaker than you wanted.
V Miller
vance3d: yes, I have done some testing and 100% reflection gives the best result by far…