Thank you Byron.

I'm afraid I don't know what "xparent" means.

I have my doubts that the ProRes clip I have purchased contains an alpha channel. I'm not even sure how I'd find that out.

My assumption is that the 2 white/black versions of the clip after the fire ring are supposed to be used as masks to create the "window" through the upper track. That would obviously be more elegant than an iris transition. The problem is that I don't know how to do it.

The adding of these white/black masks at the end of stock footage clips seems to be common practice on Pond5 etc., so it would be great to establish a method for their use in Vegas.

You use the black and white clips as you figured out as a mask. To make them work as a mask you use the Multiply compositing mode. That makes absolute black turn that part of the track below transparent.

One other tip, to get compositing such as this to work correctly in Vegas you're probably going to have to have everything in cRGB.

Bob.

Thanks Bob.

I'm still not getting it I'm afraid. Using "Multiply (mask)" mode on the track with the mask on it just makes the white part of the mask transparent. "Darken" just does the same.

Screengrab: [url=http://dl.dropboxusercontent.com/u/21489814/mask.png]



Anyone have any other ideas? An idiot's walkthrough would be hugely appreciated.

Nick, try these steps:

1. Set up tracks as follows:

Track 1: Overlay matte (multiply mask)
Track 2: Video stock fire (child)
Track 3: Background

2. Click Track FX button on track 1 and select Mask Generator tool.

3. In the Mask Generator dialog select a Luminance key from the Type dropdown. May need to click Invert checkbox to get desired effect.

4. Click the Compositing Mode button in Track 1 and select "Multiply (Mask)" from menu.

5. Click the Make Compositing Child button in Track 2.

HTH.

/jerry

Thank you very much Jerry for putting me on the right track.

Actually it ended up a little more complex than that, but I'd completely overlooked the Mask Generator tool, and that was the key to getting it work.

I don't know why images no longer embed in the forum. Here's a link to a screen grab of how I've got it working, with solid red and green replacing my clips to make it easier to see what is going on.

Tracks 1 & 3 have the "Multiply (mask)" compositing mode. Both have the Sony Mask Generator FX with type "Luminance". On track 1 I have the "Low in" set at 0.4. On track 3 I have the "Invert" box ticked and "Low in" set at 0.5. The other sliders are at their default settings.

Nick, that looks pretty cool and more complex than what I was envisioning. I'm glad you were able to figure it out and especially glad you shared your solution with the rest of us!

/jerry

Nick,
My appologies, xition = transition.

Here is a quick screen grab of the setup I initially mentioned:


Here's the result:


At this point you'd just have to adjust the speed of the transition to match the fire clip.

This has been a very useful thread for me. Thanks to everyone for their input. I have exactly the same problem as Nick: I only use the compositing feature once or twice a year, and I always have to re-learn the compositing mode, parent/child, and fX combinations needed to make everything work.

I don't think, however, that you should need to use the mask generator ...

You might be interested in this video on how to use Transquare transitions in Sony Vegas:
(4 tracks, parent/child, Multiply compositing mode and Sony Mask Generator FX)

I use track compositing quite a bit. Not for transitions normally, but for FX. Here's a transition I did years ago with a link to download the project:


And if you want to go OVERBOARD:

When you load a clip into Vegas it will come up with a dialogue pane where you can turn a clip into an alpha which means only the flame will show and everything else in the clip will change from black to transparent. The clip you linked to is photojpg and doesn't contain an alpha channel according to artist.