Superfly, render time, skydome.....

  • While fooling around with the old PW Bathroom I noticed a very relevant difference in render times.

    Both renders below are done with exactly the same render settings: GPU, 3 Samples then stop, both renders use meshlights only.



    You can see that the first image will take ages longer before it stops being grainy.

    The only difference between the two images is that in the second image the background (P11 "Construct" ) no longer is a meshlight, the ambient value is zero.
    It seems to me that Superfly will generate way more grain if there are meshlights in the scene which are mostly invisible.

    I don't know if the same is true for area/point/spot lights as well, but it seems to be likely.

  • @bantha said in Superfly, render time, skydome.....:

    You can see that the second image will take ages longer before it stops being grainy.

    Di you mean ...the second first image will take ages longer before it stops being grainy.

  • Corrected. You are right of course.

  • @bantha When you think about it, it makes sense, the renderer cannot know that light from the construct won't affect your scene, therefore it needs to do the ray traces just in case you have a window or a hole, the fact that none of the rays can ever affect your scene means a lot of rays are traced for no good reason.


  • I don't know that this is right for an unbiased renderer. You still get reflected light from the walls, so hitting them with a ray does make sense. Just shooting for the lights would be like Firefly without IDL. In fact I did not have the same behaviour from Luxrender. But Superfly / Cycles is still biased, obviously.

  • @bantha Have you tried deleting the construct altogether and seeing if that also helps with render time?

  • Doesn't make much of a difference. What matters are emissive materials, everything with ambient seems to count as a light and is checked. A lot of older sets have some ambient in their materials somewhere. The set above has water in the tub, the shader had some ambient and removing that helped again in reducing the rendering time.

    That's a big thing for eveyone who uses legacy scenes, especially if you try to do darker scenes. Some lit polygons somewhere in the scene can tripple your render time.

  • I presume it also matters how many ray bounces you allow. Could you make a screenshot of the render settings you used?

  • Possible, I will check. Here are my settings, Pixel Samples were set to three for the demo pictures: