# color filtering/tinting?? AND normals

firstly - is there a quick way to render a scene in the back buffer and then tint the whole scene as if looking through a color filter??

secondly - when creating objects you need to define the normals for lighting. What’s the easiest way to do this?

Thanks, just starting to learn opengl if ya can’t tell…

tymk

nothing comes to mind for the first one, you could always try drawing a big transluscent quad or playing with the color mask
as for the second question, normals I will give a quick explanation, but look into the previous posts on this forum, normal calculation is a really common question.
Basically you have 3 points that make up a triangle, call them A,B and C Now, from these you can create several vectors that make up the triangle, i.e. A-B, A-C etc
pick two, A-B and A-C work well, but depending on the winding of the vertices you might have to fool around. Take the cross-product of these two vectors (check any pre-calc book), thats the normal of the triangle. In order to find the normal of each vertex, figure out which faces each vertex is a part of and average them
hope this helps