Vegas needs Recipes . It has the ingredients , We just need to know how to put it all together .
this project uses Chroma Key to cut a mask . Then the mask is stuffed into the alpha channel.
Chroma key technique with Vegas :
on the Green Screen source image , open FX Chroma Key and FX Mask Generator .
In the FX Chain list , Chroma Key comes First , in the chain .
In Mask Generator , click the Invert button , because Mask Generator's only
purpose here is to invert the mask and nothing else .
In chroma key , click the "Show Mask" button .
With both ( Chroma Key and Mask Generator ) OFF , pick a color with eye dropper .
Now , turn chroma key ON . we are viewing the NON-inverted Mask because chroma key
"Show Mask" is ON and Mask Generator is OFF .
Adjust High Threshold slider to make the foreground Solid White .
Now turn ON Mask Generator to view Mask as Inverted .
Adjust Low Threshold slider to make the screen area full White .
Screen area being ( Green or Blue ) background .
That should be a good mask . Toggle Mask Generator ON\OFF to inspect both views .
Turn Mask Generator OFF , and un-check "Show Mask" in chroma key . We are now viewing the cut as a final inspection .
Stuff the Mask in the alpha channel :
Duplicate the above Track ( For use as Track 1 and Track 3 )
For Track 3 , in Chroma Key , check the box "Show Mask" , because we want to stuff the Mask into the alpha channel .
add new track into the middle of those 2 tracks , and use Generated Media Solid Black on this new track 2 .
on Track 1 ( the duplicated track ) , Chroma key is OFF( Mask Generator is also OFF ) and
set it's alpha channel to full Black by using FX "Channel Blend" .Set all 4 of the bottom row "Alpha" digit boxes to -10.000
Enable blend mode ADD , to track 1 .
Track 2 has Solid Black RGB Generated Media , with Solid White alpha channel .
Set track 2's blend mode to Multiply . Track 2 is a Parent of track 3 .
Track 3 ( the original chroma key cut ) , is a child of track 2 . Because "Show Mask" is ON
in Chroma Key , all 4 channels hold the same Mask image , thus the alpha channel has the Mask .
When track 2 multiplies with track 3 , the resultant RGB image goes to Solid Black , while the
alpha channel of this composite will be that of track 3's alpha channel( the Mask ) .
At this point we have 2 RGBA items :
Tack 1 is the original RGB image with an all Black alpha channel .
the composite of tracks ( 2 3 ) is an all Black RGB image with the Mask in the alpha channel .
When those 2 entities are added ( Track 1 uses "ADD" blend mode ) , the result is :
RGB of track 1 , with the alpha channel of track ( 2 3 ) composite , is the new entity image result .
Use Vegas Viewer icon Top right of viewer , "Save to file" , and choose .png .
that will save a 32 bit image with RGBA channels .
The Mask in the alpha channel might not line up perfectly with the original source image foreground ,
because of the external "cut" that occurs , when the alpha gets used , upon import .
Render video with video for windows .avi uncompressed , check the box to include alpha .
Makes a 32 bit .avi uncompressed video with RGBA channels .
Some .mov formats render with alpha channel .
updated : included picture number 8 , which shows how to stuff the alpha channel with any RGB source , this requires the use of FX Channel Blend , on track 3 ( No chroma key this time ) . Track 3 remains a child of track 2 . Everything else in the project remains the same . We now realize , Any RGB content can be placed into the alpha channel .