Noiseless single sample cycles renders I'm building a blender render farm as a hobby project that renders tiles on seperate computers. My plan was to have an opengl render as background for the unrendered tiles in the preview but blender in background mode doesn't support opengl renders. Now I'm trying to render a noiseless image with cycles. 

I use python to remove all materials and lamps from the scene and set ambiant occlusion to 100%. In the rendering settings the samples are the lowest possible and no bounces.

I thought that without materials and bounces that I wouldn't get noise if I render a single sample since the only lighting is ambient occlusion but I still get a lot of noise. Why?

What I get:


What I want (this is 10 samples):


For some reason the single sample render is only 3 graylevels

Is there something I forgot to tweak?
Cycles still is a approximation based path tracer. this means everything you see in the rendering is getting calculated by randomly shooting rays. per path blender is only shooting one ray per pixel (correct me if im wrong). this information contains "is this pixel getting light, or not". If yes, the pixel gets white, if not, it is getting black. this is why you only have black and white pixel at 1 rendered sample. If you shoot another ray, your information (light, yes/no) is getting mixed, so that a grayscale is calculated. the more sample pathes, the more accurate your image.

10 Samples is a good amount of samples and there is little you can do to even improve this number.

Only thing you can try is the upcoming denoiser for blender (download a WIP build here http://blenderartists.org/forum/showthread.php?395313-Experimental-2-77-Cycles-Denoising-build). But i dont think you can go under 5 samples.