I'm trying to achieve photorealistic renders with Image Based Lighting + lamps that should effect the scene locally - only the surfaces around them. In this particular case, the first render was made with IBL + only the one spotlight lighting the logo on the wall: with 60 samples I get close to the result I want.

Only IBL + 1 spotlight: with 60 samples very close to what I want

However, rendering with the rest of the lamps, 1-2 hundreds of point lights that should only effect the surfaces immediately around them (to achieve that I have set their max bounces to "0") noise gets totally out of control in the area lit by the spotlamp. The area lit by the spotlamp, the wall with the logo, should not be effected at all by the rest of the lamps, only by the spot and the IBL, so I wonder why the noise?

IBL + the same spotlight + 1-2 hundred other lights that are not supposed to effect this surface at all: 60 samples, noise totally out of control

Is there a way I can reduce noise taking advantage of the fact that, although I have many lamps, I only need them to have a limited, local effect on the scene?

I attach two more images to help you understand the scene. I use cycles, blender 2.75

Scene wireframe

Scene textured

  • $\begingroup$ I think noise is added by big amount of light sources and thus increased amount of rays cycles should compute, As follows you should be aware of using such big amount of lamps in scene (I think that there may be < 5-10 of them in most cases). Several lamps and maybe planes with emission set up (placed) correctly should give you the light you are willing to achieve. $\endgroup$
    – Mr Zak
    Jul 13, 2015 at 16:46
  • $\begingroup$ If I understand correctly, you are saying that replacing point lights with geometry that emits light would result in much less noise? $\endgroup$
    – Booth
    Jul 13, 2015 at 17:06
  • $\begingroup$ Is multiple importance sampling enabled for all the lights? If so, try disabling it on lights that contribute little to the overall illumination and see if that helps. The effectiveness of MIS diminishes the more things have it enabled. $\endgroup$
    – gandalf3
    Jul 13, 2015 at 19:01
  • $\begingroup$ No, I didn't mean to replace all lamps in the scene by planes with emission, rather that reducing lamps quantity, because it's way too much of them there. Possibly you can substitute some lamps with emitters, but it depends. As I get it now you are trying to achieve some kind of ambient occlusion with those lamps and IMO it isn't as it should be $\endgroup$
    – Mr Zak
    Jul 13, 2015 at 19:20
  • $\begingroup$ @gandalf3 : I think I have tried both with and without MIS, but will try again to make sure if it makes a difference and will update you. Anyway this is good to know, I wasn't aware. $\endgroup$
    – Booth
    Jul 13, 2015 at 20:19


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