I wrote this definition for the purpose of copying pictureframe surfaces in architectural scenes (people, trees, cars, etc...), and orienting them towards the camera for use with multiple views. Instructions are included within the definition and should be pretty self-explanatory. Let me know if you have any questions, and I hope it saves you some time!
The file is called "OrientToCamera_v1.0.ghx." You can get to it by following the link below, or by looking for it on the Files page. http://groups.google.com/group/grasshopper3d/web/OrientToCamera_v1.0.ghx?hl=en
