I'm creating an app using image targets that allows the user to point their camera at a printed page and see hidden content. I'd like to create a "magnifying glass" effect in which I have a GUI element overlayed on the screen that looks like a magnifying glass and I only want to render the ARCamera's feed into the magnifying glass' circle and have a second camera that renders the camera feed around it.
1. AR Scene with image target
2. GUI element that looks like magnifying glass
3. Second camera to render the non-AR camera feed
I'm trying to figure out the best approach to take in Unity to create a circular "scissor box" effect. I'm thinking I'll need to create the magnifying glass image with an alpha-to-grayscale setting enabled in the inspector and then have the ARCamera render only the part of the screen within the alpha-masked circle. Another strategy was to create a scissor box effect (which does not come out-of-box with Unity) and then add some sort of vignette effect or something to that area to mask out the hard right angles caused by the box.
I've attached an image to show what I'm trying to accomplish. Any suggestions or examples would be great.