You might have to use some tracking mattes to fill in the keyed out color.

Dave T2

I'm not sure I follow you. You have "3D meshes" that you want to use within Vegas? Vegas doesn't support 3D objects / rendering. You would need to use the 3D objects with a 3D application like Lightwave, etc. Then render to an image sequence in a format with an alpha channel (e.g. PNG). It won't matter what colors the object uses.

If they are true primary red and green then true primary blue is your friend here. These are different than either perceived or pigment red, green, and blue.

The vectorscope is your best tool in this case. Shoot against a neutral background and aim for the empty side of the triangle for your background.

Or per monoparadox, you can alpha the background and proceed with confidence.

"I recently downloaded some 3D meshes of various Star Trek starships to use in a video with a chroma key background"

Can you elaborate on that please.
It sounds to me like you are going to shoot a video with a chroma key backgorund and then into that you wish to adds the starships.
If I've understood you correctly then use the usual green screen when you shoot your video. CK out the green screen as per usual.
Then you take the 3D meshes into your CGI app and render them out as PNG or whatever supports an alpha channel. Add that video or still images either on an upper track (they'll appear in front of the talent) or lower track (they'll appear behind the talent).

However if you can only get your starships without an alpha channel then try putting them onto a superblack background (0,0,0). Most likely nothing in the rendered model will be that black. Now put them on an upper track and change and you can use the CK'er to key out the absolute black.


Bob.

Sorry for leaving out some vital details, my mind has been going in several directions at once, and sometimes one of those directions veers off the road.

Anyway, I want to create a small animation within 3D Studio Max with the 3D model of the starship. Then take that AVI file and put it into Vegas and a moving star field behind it. Normally if I do this kind of thing, I'll set the background color in 3D Studio to green, but as I said there is one green running light on the port side of the ship (or is it the starboard side?) and that light also reflects a small circle of light on the hull. Which would give the final effect of making the ship look like it's got a hole in it.

If you're familiar with Star Trek's Enterprise E, from the Next Generation movies, you'll know that the ship has red warp nacelles, a blue deflector dish, and several other colored areas on various parts of the ship.

I use 3D Studio mostly for modelling, so I'm not sure if it has an alpha channel output as someone suggested, but I'll check that out. If not I guess I could try creating a mask around the one green light and just use green as the background color, but it's an extra step I was hoping to avoid.

When you export select Quicktime = compression png then select million colors +. the plus is the alpha channel

When you import this into Vegas right click on the media and select alpha channel as straight.

"I use 3D Studio mostly for modelling, so I'm not sure if it has an alpha channel output as someone suggested, but I'll check that out"

I've never used 3DS but I'd be amazed if it didn't have te ability to create video files with an alpha channel, even the free 3D apps can do it plus they can output another video file thats a B&W mask that you can also use to create transparency in Vegas.

Bob.