Masking is better done in event pan/crop. There's a checkbox for that.

Not sure what you want to accomplish, but

Source Alpha only works if you already have an alpha layer. It appears you do not.

I have a greyscale image. I want to map it to the alpha channel of a video file. How do I do this in Vegas?

In Photoshop, select an area or gradient to be made transparent, and Export Transparent Image.

Not something you can do as much in Vegas, which can only work with existing alpha layers, and then not all the time. You can replace certain colors with transparency, as well.

You can create "some" transparency in generated images in Vegas with masking, opacity, and backgrounds. Mostly for graphic not artistic effects.

Have you tried track opacity yet? (Reset all tracks to source alpha first.)

Yes, compositing may be what the OP wants, and I suggested he start with opacity.

That's different than masking with an alpha layer in my vocabulary, which is what he said he wants.

Without knowing his exact intents, your example might just be the ticket, thanks.

I have a greyscale image. I want to map it to the alpha channel of a video file.

To my understanding thats exactly what GIMP or Photoshop does with a layer via adding a layermask.

I showed an example how this can be achieved in Vegas.

Let's call it then compositing.

You're right, I really don't know what to call working in three source layers as distinct from four, and as usual there's lots of overlapping terminology. I could be the mixed-up one here.

Thanks for helping the OP with your example, that's what matters.

No problem 😉

klt

This is the type of artistic effect I imagined the OP was going for, using Source Alpha channel in a grayscale from Photoshop. I wouldn't know how to begin to do this in Vegas, nor attempt to demonstrate the steps to get there.

That said, Vegas' native masking and compositing is great, no complaints.

Also, sorry for duplicate pings. I was having trouble uploading the image.

Nice picture.

Hmmm....

Depending on the source pictures I think it's doable in Vegas. At first look it would take 5 to 9 tracks. Less, if the background is one pic, or more if the sky and sunflower land are on different pictures.

Not something you can do as much in Vegas,

Not necessarily correct.

@dan9er, yes, you can do this in Vegas.

I quickly assembled a quick and dirty test project, where the gradient represents a BW image you want to use as "alpha". The orange represents the thing you want to mask with it, the gray represent everything below it.

Of course, you can have more tracks as child tracks, as well you could have a BW video as mask, not just a still image. If you need a video as that "mask layer", that would be huge work in Photoshop or such.

So the quick and ditrty tutorial, I hope you get the idea:

I finally understand why it wasn't working. I was using the wrong button this entire time.

I was using the button I circled in red, where I should've used the button in blue. I didn't notice this because as you can see in my original post I've hidden the buttons (since I never dealt with compositing before).

Thank you @klt.

PS. I personally think the other compositing options (stuff other than source alpha and multiply) are pretty useless, but in my study into this compositing feature I found out this child/parent system can be used to do "layered keyframes", which is very useful for what i'm doing.

You are most welcome.

stuff other than source alpha and multiply

You just don't need them right now. At the first moment you try to make a sabre light battle you will find "add" useful for example. 😊

I'm glad I could help and Vegas is your tool to make your dream come true. It is so much more capable than simple gameplay videos.....

@dan9er

Would you please post your result so I can see what you were after?

When your thread topic originally said, "Attempting to mask with mask image: Source Alpha not working" I presumed you either were, or wanted to work with a transparent image rather than a vignette shape.

Glad you found your solution!