Version 1.3 of RapidShader will be ready soon. One of the new features is included ‘Vertex Shader Snippets’ which allow you to select a predefined vertex transformer; already included is a new ‘billboard’ option!

Using that and some offset textures I created the images below.

The old warp effect is back:

A cool bulging effect (the opposite is also possible for an inwards portal effect):

And also interdimensional travel!