Hi Neil
Attached JPG shows a render from a perspective camera and on the right an ortho camera. Analytic cylinders show an incorrect dark artifact that is not possible from the lighting.
I noticed that your scene is huge in size. Select the "root" level, open property window, scale all dimensions of the "object space" by a factor of 0,0001 and render. This removes the artifacts from your example column, at least.
I suspect that the ray tracing calculations for shadow rendering go wrong due to rounding errors, when dealing with such a big scene. I think that the optimal dimensions for a scene are of the order 1.
Cheers Jyrki
