Support for "Shadow Catcher" Effect

The upcoming release of Blender will include a new feature known as "Shadow Catcher" which can be applied to objects that are unseen other than the shadows cast on them. This is often used for product placement where the product needs to cast a "Studio scene type shadow" with an alpha background to composite over a scene image or a simple background color. The coming feature is part of the Cycles Engine.

I am hoping that this functionality could be implemented in Blend4web.

In video compositing, this feature is used to give the illusion that the shadow is cast upon the background video or image. In real-time rendering, you actually have the object that should be receiving the shadow already rendered in 3D. So why fake a shadow when you can do it for real?

True, I guess I was just liking the idea that anything could happen in the background. I like the idea of having a ground shadow that can have anything behind it; whether that is an image, a video, or just a way of animating color changes, it just seems like a nice easy way (in theory) to have more freedom and control over the way a scene interacts. (And could also be overlaid over non-Blend4web objects.)

Perhaps I don't understand a current workflow that would replicate this scenario:

Having a simple ground plane that will catch ground shadows; but not have any visible area where it shows an edge/horizon etc. I know that it is possible to create an environment half dome with a truncated area where the dome changes into a ground plane; though it still looks stretched and a little forced.

I do realize that the phrase: "the idea that anything could happen in the background" might give developers nightmares; but as an artist, I always look for the greatest potential . . . .

;)