Compositing Lightwave characters into Final Cut Pro

[Slash5]

Hi,

This is a pretty specific question about compositing, so I don't even know if I'm in the right forum.

Anyway here goes,

I want to put 3d characters that I've created in lightwave into real time video footage that I've shot. The camera was in a fixed position btw. The tricky part is that I want to keep the shadows that the characters are already casting on the ground, then having those shadows appear to be casting on to the ground in the video footage. I'm thinking it's got something to do with rendering the alpha and RGB frames in lightwave and then bringing them in FCP.

I just know this is an incredibly common form of compositing, but I have know idea who to ask :(

Can anyone here help me? Or tell me were I can ask?

Thanks, Chris

[aloysius1001]

This might work. Render a seperate shadow pass, set your character to unseen by camera, make the ground white. when you go to composite you should have white ground w/a black shadow cast by your character, but this is the opposite of what you want so invert the layer(or whatever they call it in FCP). If you need shadow transparency, adjust the output to pull the black closer to gray. Like I said this might work, I haven't tried it yet so let me know if it does.

[fester]

or you could set the ground plane's alpha channel to shadow density under the advanced tab in the surface editor. Make the ground plane black, or a dark color. The alpha channel will then only see the areas that have a shadow on it.

You could combine this with doing the shadow as a separate pass - making the object unseen by camera. Then you'll have just the shadow to composite as you like, and the alpha channel will have only the shadow, so you don't have to worry about transfer modes or anything, you can just adjust the opacity of the shadow to how you want it.

good luck.

[Pensart]

Keep in mind that the alpha channel trick does not work with global illumination :mad:

[munky]

I'd render your figures with an alpha. Then I'd render the shadows as a black and white image that you can then luma key in fcp . Separate layers always give you the flexibility to soften /blur use as adjustment layers so you can sit things into the pictures better.

Try the Highend2d website or creative cow for comping tips. Issue 25 of 3d world had quite a good article by bill flemming all about 3d compositing.

hope this helps

paul