Overlays: YOU'R DOING IT WRONG! (me doing it wro

wwjd wrote on 3/20/2015, 11:19 AM

I thought I knew how to do it: have a track with video, slap a track above it (explosion whatever) with BLACK background, say ADD or OVERLAY (I forget which this second) in that pull down menu and it shows up OVER the lower video. Perfect. Now I try that and the videos seem "blended", not overlaying it - I can see the lower video through the top video, like the top is more translucent. Didn't think I had that issue in the past.... maybe I didn't notice? I tried many different combinations of that pulldown menu for ADD MASK OVERLAY etc, but can't seem to get it right.

Am away of using the ChromaKeyer to blot out the background, but never had to do that before for some reason... is that the ONLY way to be sure the top track fully blocks out what it under it? -- except the black background of course that is filled with the lower track.
Now I'm confused

Comments

Chienworks wrote on 3/20/2015, 11:34 AM

Add and overlay are effects that blend the two images together. You should see some remnant of the underlying video when using these.

TheHappyFriar wrote on 3/20/2015, 2:32 PM

I normally use an Alpha channel.

wwjd wrote on 3/21/2015, 10:14 AM

I usually leave the lower track on ALPHA (I think that is default?) and put ADD on the upper.... is there a better way? I'd prefer the upper track to NOT be "see through"... but maybe I am talking about using the chroma key to blank out the black background properly?

Thanks for any help.

TheHappyFriar wrote on 3/21/2015, 12:04 PM

I'm saying normally my upper track has an event with an alpha channel and I use that & leave the track as is. I sometimes have a separate file of an alpha channel & then use two track to get my composite, but I don't think I've ever had a black background & just used the "ADD" blend method.

I've used Vegas to render out some PNG image sequences with alpha or a QT MOV with PNG+Alpha for stuff that didn't have an alpha channel (like an explosion).

jerald wrote on 3/30/2015, 12:37 AM

If your overlay video non-background content is of completely separate luminosity than background (like a flame overly would be, for instance), there's technique I use that's easy to configure (usually) using the Sony Color Corrector (Secondary) effect.

For following description assume overlay clip is black background, with flame image that is desired to appear over lower track. Both tracks set to composite mode 'Source Alpha' (default).

method:
On upper track, add Sony Color Corrector (Secondary).

In effect settings, click on 'Select effect range' button and drag cursor over a part of the background. to tell effect the range it is to use for secondary mask.

Check accuracy of secondary mask by checking 'Show mask' in effect settings.

If necessary, play with mask settings under luminosity, saturation & hue categories to tune the mask.

Once the mask matches the desired background area, uncheck 'show mask' and move alpha slider all the way left. You should see your lower track and upper track composited as desired.

That is the basic technique.

It can be very easy to use in circumstances in which it is possible to isolate desired- and undesired-visibility regions via any combination of the three categories of secondary mask (i.e. luminosity, saturation, hue).

In some situations using this technique, it may be easier to use the 'Invert mask' checkbox _after_ tuning the mask to match the _desired-visibility_ region. It just depends on how it works best.

Hope this helps.
J

wwjd wrote on 3/30/2015, 9:53 AM

thanks, I'll check this out. I still didn't get it to work as I wanted, but it is passable and nobody but me would notice

larry-peter wrote on 3/30/2015, 10:56 AM

If you want to only use Vegas' native plugins, this is a good way to do a luminance key (which is what you need for compositing a clip with black background and maintaining control over the opacity of the key):
https://forums.creativecow.net/thread/208/880904