The Washout

[fleetwood]

Many Thanks for all the information Oshyan,

Keep in mind the intent of  my initial render is as a test and way of learning what it takes to convert older cloud layers that worked well in T3 to similar looking layers using the new clouds of T4.


Obviously, the intent of using 0 voxels was a baseline test needed to establish what would otherwise be an unknown. Frankly I'm fairly surprised to see any cloud effects at zero, but there is certainly something produced other than blue sky  .

Having no access to the design or code being executed, I'm in the position of examining what amounts to a black box so bear with what seem like foolish tests to you. In first tests with unknown parameters I will always try zero or negative values in order to know what happens at the extremes.

The five layers from top down are :
1. high pinkish wispy layer
2. a yellowish wispy layer
3. darker gray cumulus layer
4. rain virga  layer stretched in Y and also rotated to slant it
5. ground fog layer

I used cloud GI set at still/very high because it is the best available setting, I don't have pre-knowledge of what it will do (again these parameters are like a black box to me) , and my personal inclination is always to try out high settings.

I used GI prepass values of only 1/1, not because of noise but in an attempt to lower the horrendous prepass times I was getting which took 8 hours to run before even one final render bucket would even start to fill.

[AP]

Another observation I may add is that the render has an old oil painting look to it. Those deep rich earthy tones.

[Oshyan]

Understood fleetwood, it's good to know the context of your experiments. A couple of responses:

I understand your inclination is to use "the best available setting"/high settings, but you also appear concerned with long render times. I would suggest *not* using "high settings" as a general policy, at least not until you have determined they might be necessary. If you do continue with the "use high settings" policy, you will inevitably experience not just long render times, but - perhaps more importantly - longer than *necessary* render times. Often times a high setting is useful or necessary for particular circumstances, but will literally produce no visual difference in rendered output in other circumstances, so you end up rendering for a long time for no discernable benefit. This is the cost of defaulting to high settings and not focusing on optimization and understanding how the quality and detail settings interplay. Of course I understand that testing can lead you to such an understanding, but I'd suggest starting with tests of lower quality first, at the least.

As for the GI prepass and your long prepass time, it's important to know that those settings do not affect cloud GI. If I'm not mistaken setting it to 1/1 probably won't notably reduce render time which is likely up at 8hrs due to the "very high" setting for *cloud GI*. Reducing cloud GI would probably give you the best improvement in GI prepass time.

- Oshyan

[fleetwood]

Thanks Oshyan for the ideas.
Really my main concern is almost always final image quality not actually render time. I accept long render times if I understand why I'm getting it and the end results are there. At this point with the new parameters I haven't tested enough t be at the "understanding why" stage. 

I have the render (still noisy) down to about 5 hours now but have more tests in mind.