rendering problems (alpha, shadows)

I’m a newbie with a question or two that is probably annoying to advanced users, but please bear with me. I can’t seem to render with an alpha transperant background, and my objects are rendering with shadows just beneath them. I hit the RGBA button in the format panel, and killed the material link to world backgrounds, and still no go. Do I have to render out and then key out a solid backround? Thanks to anyone who can help.


The background will be transparent if you enable RGBA and save the image in a format that supports an alpha channel (e.g. png). Most image viewers will ignore the alpha channel and just show the sky colour (if Sky was enabled), but if you load the image into an editor (e.g. GIMP) you will be able to see the effects of the alpha.

Thanks, raw pigeon. I have been rendering my files as a Matrox I-frame + Alpha, since I have Adobe prod. prem. and the matrox RT.X2 enhancement. It doesn’t have the alpha when i import into Premiere Pro. Is it an incompatibility of Blender to use this codec?

Are you rendering a still image or a movie? I had this problem rendering a quicktime, and the advice I got was to use the RGBA button, and to make sure the codec is “animation”. I had been rendering using “none” as the codec, and I think that was the problem.

Hi, Elin.
I’m rendering it as a movie, and when imported, the file plays on the timeline, but no transparency over other video files. I’m wondering if there’s a problem using the Matrox I-frame HD + alpha codec. The animated objects are nice and razor sharp, just no alpha. It works great in After Effects, but then again these codecs were designed mainly for Adobe apps.
Thanks for the reply!

Sorry, I’ve no experience with that format. Could you render to a series of images and use an Adobe app to compile them into an animation?

ryancoston, do you have “Key” turned on in your Render settings? (next to Sky & Premul) That’s what I use when I need something rendered on an alpha. They look funny in Blenders render window, but on importing have perfect alpha.