Issue with basic Composite/Roto node setup

I’ll try to make this brief. I’m on MacBook Pro M1 Max 64GB. Have latest version of Silhouette installed as OFX for host Fusion 18 (latest version).

I am reading PDF and following along in Tutorials section on page 203 - Compositing and Multiple Nodes.

I have FG and BG images (same setup as shown in the PDF images) connected to a Composite node and BG is connected through a Roto node. All good so far.

However, when I create a spline in Roto node, and then view through Composite node View, nothing happens. I can still see the FG image completely. PDF states you should now only see what the Roto spline is set to show.

Move connectors around to see what’s what and the only way I can make it work is by disconnecting the BG image from the Roto node and only having the Roto node connected up to Composite’s Obey Matte or Composite 1 Matte input. No image can be attached to Roto node and it show correctly in the Composite View. So, either the PDF is wrong, something changed in Silhouette behavior or I can’t do a simple FG over BG composite with a matte.

Now that I have it were the Composite View is correct, how do I add a Transform node to my FG image? Because it looks like the Roto node is cookie cutting the BG image and when I transform the FG image, it moves behind the BG image?? Nothing makes sense.

Any help would be greatly appreciated. Thank you.

It sounds like the clip you are connecting to the Roto node has a an opaque alpha channel. To fix this, select the source clip in the Trees window and in the Node window, set the Alpha > Fill to Transparent.

Thanks, Marco. It was the FG image that needed the Fill > Transparent on it. And I reversed the Roto to be on the FG image, in order to get a Transform to work correctly. Takes a minute for the mind to come out of one compositing app into another and have to wrap the brain around how the new app works.