Convergence barely progressing in a scene with few lights?
artsinis.san
Posts: 8
Hi community,
I'm doing (or trying to do) a few scenes from the inside of a club. Mostly dark surfaces, no windows for a HDRI environment, few emissive lights for the scene and some ghost lights for the character. To finish this render Daz takes more than double the time and iterations than it does for a better illuminated, very heavy scene with many characters and objects. The render also makes barely any progress sometimes, see here (I missed the start, but it quickly jumped to ~20% Convergence in a few Iteration):
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 20.21%
Iray (Iteration) : 192
Iray (Iteration) : 220
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 21.46%
Iray (Iteration) : 252
Iray (Convergence) : 22.15%
Iray (Iteration) : 284
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 22.75%
Iray (Iteration) : 316
Iray (Convergence) : 23.37%
Iray (Iteration) : 350
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 23.97%
Iray (Iteration) : 387
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 24.76%
Iray (Iteration) : 428
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 25.33%
Iray (Iteration) : 473
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 26.14%
Iray (Iteration) : 522
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 26.79%
Iray (Iteration) : 576
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 27.56%
Iray (Iteration) : 636
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 28.14%
Iray (Iteration) : 702
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 28.53%
Iray (Iteration) : 774
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 28.79%
Iray (Iteration) : 853
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 28.82%
Iray (Iteration) : 940
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 1035
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 1139
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 1254
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 1380
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 1518
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 1671
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 1840
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 2026
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 2231
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 2456
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 2704
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Iteration) : 2978
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 31.89%
Iray (Iteration) : 3279
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 36.74%
Iray (Iteration) : 3611
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 43.60%
Iray (Iteration) : 3976
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 51.19%
Iray (Iteration) : 4374
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 57.46%
Iray (Iteration) : 4812
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 62.50%
Iray (Iteration) : 5238
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 66.28%
Iray (Iteration) : 5648
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 69.78%
Iray (Iteration) : 6041
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 72.82%
Iray (Iteration) : 6423
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 75.57%
Iray (Iteration) : 6788
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 78.13%
Iray (Iteration) : 7137
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 80.27%
Iray (Iteration) : 7468
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 81.95%
Iray (Iteration) : 7779
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 83.64%
Iray (Iteration) : 8073
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 84.92%
Iray (Iteration) : 8353
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 86.00%
Iray (Iteration) : 8617
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 86.95%
Iray (Iteration) : 8868
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 87.72%
Iray (Iteration) : 9110
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 88.56%
Iray (Iteration) : 9342
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 89.24%
Iray (Iteration) : 9566
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 89.93%
Iray (Iteration) : 9780
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 90.62%
Iray (Iteration) : 9986
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 91.26%
Iray (Iteration) : 10182
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
Iray (Convergence) : 91.78%
Iray (Iteration) : 10368
Iray (Canvas) : Render target canvas was written.
Iray (Scene Traversal) : Initializing update
Iray (Scene Traversal) : Retrieving journal and checking for changes
From Iteration 940 to ~3000 there is like no progress. The same thing happens towards the end of the render. This seems to me like Daz is spending iterations on... nothing? Can someone please explain why this is happening?
On that note: Is there anything I can do to speed up render time wihout sacrificing the render quality or illuminating the scene so that it ends up brighter than I want it to be? Any render settings you can recommend for dark scenes? I just realized I'm lacking experience with these. 
Thanks in advance.
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Comments
I would suggest adding more general light, and then change Tone Mapping in Render Settings.
It will take a very long time to get a scene with insufficient light to render.
Convergence is a measure (guess) of how close to settled the value of a pixel is. A light path that has high values will make it brtight, one with low valus will dim it, and the average is used as the pixel value. If you have few, concentrated lights then many areas will be hit only occasionally and so their values will take a long time to reach a stable average.
Thanks for the reply and confirmation. May I ask what a "general light" is?
Okay, I guess I should try making the scene brighter and playing with the exposure value and shutter speed.
Thanks for the explanation. Do you have any idea why the percentual gain is so inconsistent throughout the render progress (in this case it starts fast, gets slow, gets fast, gets slow again)? So far I only had renders that started slowly and got faster or started fast and ended slowly.
So I need more light sources and can't just turn up the luminance on the existing ones? I think I read somewhere that the light path starts from the camera and needs to hit a light source at some point for the pixel to get a value... Which means an emissive plane at the ceiling might be the best way to go?
With general light I meant a light that will light up dark areas. In reality you would do it with a number of lights, each with low intensity, so there don't disturb your overall lighting, but ensures that the dark areas not are taking a very long time. For that I will often add some emissive planes. If using normal light, make sure that there light dimension is large enough to avoid/blur shadows.
Because it depends on pixels reaching stable values (how fussy it is about what counts as stable is determined by the render Quality setting - which is all it does) then it is possible for some areas to settle rapidly and others to take longer, and so ther percentage of pixels that have settled (converyged) does not increase smoothly.
Yes, if that is the look you want (or can accept,then tweak later - in which case you might want to enable Canvasses in the Advanced tab of Render Settings, then add a Beauty Pass canvas - that will give you a high bit-depth .exr file which you can adjust more radically before getting posterisation than the standard 8-bits-per-channel image saved from the render pane).
Thanks for the awesome support and all the tips and tricks. I already played around with adding more and adjusting lights, but I'm not happy with the result yet and will tweak it bit by bit. ^^