I was reading a paper on screen space ambient occlusion used in the Toy Story 3 video game ( http://advances.realtimerendering.com/s2010/index.html ) and they say "We use line integrals, which allow us to sample in 2D rather than 3D". What exactly does this mean? Can you guys provide me with a very straightforward example?

Thanks!

I think it means that they are trying to determine what fraction of the sphere is in front of the geometry drawn, and they do that by taking a 2D grid of segments in the z direction and checking what fraction of the points in those segments is in front of the geometry drawn. For each segment you just need to check the z buffer at one pixel to get your answer. I believe that's what they are talking about.

In other words, in order to compute a triple integral, you discretize the x and y coordinates and look at it as a sum of line integrals.