GUI Feedback Loop Helpers

This feature idea has been discussed a bit in various fora:

In short: Make it possible to select a literal number in the editor, provide a simple GUI element for changing the number using e.g. mouse movement and in real-time see the corresponding results in the 3D view.

The idea comes from Nate Robins excellent OpenGL tutorials at https://user.xmission.com/~nate/tutors.html

Another incarnation of the same idea has recently surfaced in this talk by Bret Victor: http://vimeo.com/36579366