Vignette with alpha?

Is there a straightforward way to apply a bcc vignette and apply an alpha to the edges rather than a color?

Creating a photo slideshow and want to have the photo edges blend into a background that isn’t a single color.

Hi, just had a play with this, i’m a total novice but was interested.
a lot of the effects have Mocha / Pixel chooser mask, you could put on the vignette (or not) then add a mask to make the edges transparent,
I could have sworn i saw an edge effect where you can make the edge colour transparent.
maybe Make Alpha Key or one of those Alpha masking fx would do you,
but BCC+Composite has some useful controls

I’ve tried using a mocha spline for this but keep running into what I think is a bug in the sizing of the spline. I haven’t had the time to work on gathering data for two independent bugs at the same time so was trying to avoid using mocha for the moment :slight_smile:

I’ll give +composite a shot. Thanks :slight_smile:

I would suggest using the PixelChooser filter for this - you can set it to generate a soft alpha edge. To achieve the result you’re looking for :

(1) apply the pixelchooser filter to the shot
(2) set output to alpha channel
(3) set matte to none
(4) set mask shape to rectangle
(5) position the rectangle over the image so that the inside of the shape will serve to protect the shot while the outside will become the alpha channel
(6) set the mask feather to the desired amount


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@PeterMcAuley Thanks Peter. I’ve tried that and thought that would be the answer but I’m starting to think the problems I’m having with BCCx is down to my drivers.

I haven’t had a chance to really dig in and get reproducible steps but at least 3/4 of the time I apply a spline using pixelchooser, the area that gets masked is a lot smaller than the mask.

I may have more time tomorrow to dig in more.

Hi, the size difference is poss because the picture your using is a different size to the project screen size (1920x1080) ,
Go to the top of the preview screen & Save Snapshot to file, that will save it as a png will put a transparent alpha channel down either side of your pic making it the same size as the vid project,
then reimport into the timeline
Or you could do as Peter suggests which is easier & better, no need to save as png :rofl::rofl:
Thanks Peter i learnt something today :grin:

@gid.joiner here’s the fun part…

Sometimes the mask works perfectly along the edges of the photo in both mocha and vp.

That’s why I haven’t reported this as a bug. Haven’t been able to nail down the conditions when this fails

Is that Pixel chooser or Mocha mask?
from my limited experience it’s normally a problem with Vegas or a conflict in some way like the size difference i mentioned,
Vegas is often a bit rubbish getting stuck & needing rebooting to clear out temp files :unamused:

Have you tried setting the viewer to 1:1 to see if the mocha mask that you’re using will render correctly when viewing the full resolution image?

@PeterMcAuley if I choose “match aspect ratio” in the pan/crop panel, the mask is the correct shape in VP though I’m missing much of the image.

@PeterMcAuley Here’s another data point and part of the rabbit hole I got stuck in. Sometimes the spline mask works just fine.

Here’s a mocha mask that looks just like I want it to.


I wanted to add a bit of motion to the image to make them less static. That meant I needed to shrink the mask slightly at the beginning. As soon as I did I got the problem result shown above.

The spline shown here was modified at one corner just to show the end result.

@michaelh Cool … thanks Michael. So looking at the display window, I can see that it’s a 1920 x 1080 project but the value in the display dialog is 613 x 345. Is this a zoom setting that you have control over? If so, what happens if it is set to 1920x1080?

@PeterMcAuley That’s just the size of the preview window itself. Honestly not sure why VP displays that. If I resize the window, the image within scales as you would expect. No sudden shifts in any of the elements such as the mocha spline.

We were replying at about the same time so just in case you missed this second reply… Vignette with alpha? - #11 by michaelh

I think a lot of your problems with Mocha are as i wrote above, the pic your using is a different size to the project size, it doesn’t matter what you do in the Pan/Crop box, until it s rendered out Mocha will see the orig pic size.
‘Go to the top of the preview screen & Save Snapshot to file, that will save it as a 1920x1080 png, it will put a transparent alpha channel down either side of your pic making it the same size as the vid project,
then reimport back into the timeline’

@gid.joiner I appreciate the workaround but what’s happening is clearly a bug.

In this example, the effect works as expected over 50 images of differing aspect ratios on the same track.

It’s when I change one point that things go sideways. In this project. Oddly enough, if I start from scratch, it fails every time.

I mentioned in another bug thread that if I were on a deadline I’d go for the workarounds but since I’m not, I want to do what I can to nail down details to help Boris find the source of the issue.

@PeterMcAuley Here’s an interesting twist. If I put the fx before pan/crop in the event chain, the result doesn’t change but the preview in Mocha does…