I wanted to make a Portal VFX for a long time. Currently the Portals cameras are not programmed so they don't follow the player's viewpoint but everything is ready for the implementation.

Portals use a single quad. I tested using the new decal feature in the Universal Render Pipeline for the shader implementation, but I abandoned the idea because the custom HLSL node used for the unlinked effect doesn't work properly.

I have several theories about why it doesn't work using decals. I think it doesn't work because decals are applied in screen space and I'm trying to access World Space coordinates for something that is proyected.