PDA

View Full Version : preparing a scene for compositing - suggestions?



Algae998
11-18-2007, 04:14 PM
Ello one and all,

Im finally sort of at the point where I am compositing my rendered scene with live footage. Ive seen a lot of very smooth and convincing videos around the web of other's work but I cant figure out how theirs are so fluent.

When I render my scene, with a black or a bright green backdrop, I find it very difficult to get a nice crisp color keying in after effects when I composit it with live footage. Is there a way to render with no color, or transparency as the backdrop? Or better yet, render with the live footage added in?

Secondly, is there a way to make a plate or surface for my model to stand on that is invisible but accepts shadows? I dont know my way too well around all of the menus but Id like to have my model standing on my table with a nice shadow underneath.:D

thanks in advance!

G M D THREE
11-18-2007, 07:29 PM
Please tell me you are not rendering on green and than keying it in after effects. You should know that there is a thing next to RGB, called alpha channel. That is a 4th channel containing transparency information. That you can save out of LW. If you render to a image seq. Just choose any image format that supports alpha, like png, tga or tiff for example, they are marked with 32 in the pull down menu. If you render as Qucktime choose Millions of Colors+, the "+" stands for alpha.

This way when you load it into after Effects the background will be see-true!

///

G M D THREE
11-18-2007, 07:41 PM
the backdrop? Or better yet, render with the live footage added in?

Secondly, is there a way to make a plate or surface for my model to stand on that is invisible but accepts shadows? I dont know my way too well around all of the menus but Id like to have my model standing on my table with a nice shadow underneath.:D


About the shadows. I suggest to render them in a separate pass. Create your ground plane, make it black 0'0'0', 100% defuse and than in surface editor under the advanced tab set Alpha Channel: Shadow Density. Than select all objects on your ground and open the object properties, under Render tab make them unseen by camera.

When you render a frame it will look all black, but in the alpha channel you will have your shadows!

Make sure you trace shadows or have shadow maps on.

Good luck. ///

Algae998
11-18-2007, 11:56 PM
Haha, thanks for the help, I figured it would be something simple like that. Im still pretty new to "3d" rendering (seperate alphas, shadow passes, etc..) as oppose to an "after effects" render where everything is all said and done in one render. Ill cetainly give that a whirl.
Thanks