L-o-n-g render times when using extra light sources.

[masonspappy]

I'm perplexed and would appreciate feedback, opinions, etc.
Image #1 (normal daylight)  took something less than 2 hours to render.   (1280x860 pixels)
Image #2 took 11 hours to render (1152x864 pixels)
I'm kind of surprized at the 11 hour render time, and I'm wondering if this is typical/expected when using extra light sources as I've done here?
Comments & advice are appreciated.
- Cam

[Upon Infinity]

I was running some similar tests a number of weeks ago.  What you might want to try doing is toying with the "Receive shadows from surfaces' checkbox in the quality tab of the atmosphere shader.  Also, try taking 'glow in atmosphere' off of all the interior lights.

[Oshyan]

Without knowing what your render settings were it's pretty much impossible to say why this might be, but I can at least say that adding a light source shouldn't increase render time by nearly that much.

- Oshyan

[Matt]

Reducing "max distance" on each light source might help. Just how much to reduce it depends on how far from the light source you want the light to travel, but in your case I would guess it could be less than 20 metres. The following rule of thumb might be useful: put the max distance slider a little to the left of the strength slider.

Matt

[masonspappy]

Thanks Matt, Oshyan and UponInfinity for your replies.   Matt, after adjusting the max distance settings on all lights my render time dropped to 2 hours. HUGE improvement.  Thanks!!
- Cam

[Seth]

Considering the tests I made the last months on lights, it is the shadows created by lights that cause the explosion of render time, not the lights by themselves. If you use extra lights that do not create shadows, the render time is decent (for example if you use 4 or 6 extra suns not projecting shadows instead of GI, the render time is pretty short)

[masonspappy]

Thanks Seth.  The image I'm working on is object-heavy. For example, a house made in blender where each exterior board was created and textured individually, and then slightly angled to make them overlap.  Plus grass and plants created in xFrog.  Bottom line is that there's about 10 light sources and an awful lot of nooks and crannies where shading would be a factor, so what you're saying makes a lot of sense.