A way to estimate render time?

[derei]

I'm wondering if it's possible to estimate needed rendering time for Easy-High presets (maybe based on Prelim. speed?). It would be really nice to have a estimation before choosing. I was in the situation to render Easy+, then Medium+, and finally to go even on High because first two did not shown as I expected. So first two renderings were just time waste and I did that exactly to save time . So, if we could have a time estimation, It would be more easier to choose best time/quality preset, without too much experimentation.
Also, for progressive can be estimated the time needed to achieve a certain number of passes? (I usually use 100-300 pass, depending on scene).

[Fletch]

With progressive, it's linear - so let it go through 5 passes, and divide by five. Multiply the result by 100 for time to get through 100 passes.
Due to AA time being a complete wildcard it is basically impossible to predict render times for Easy 1-7 as far as I'm aware.

[derei]

Due to AA time being a complete wildcard it is basically impossible to predict render times for Easy 1-7 as far as I'm aware.

So, AA for Easy can't be used to extrapolate AA for High+, for example? There is no way to "guess" how long will take a better AA, if we know how long lasted the most basic one(or some other significantly lower setting) ?
If I'm not mistaking, I remember a friend of mine used Vray and there was a total time. He always knew when the rendering will finish.

[Fletch]

This capability, while much desired, does not currently exist in the render engine. sorry!
No, knowing the AA time for a low render setting can not ( I don't believe) help extrapolate the render time for "High".
However, we could run some experiments and see if we can come up with some sort of "rule of thumb".

[derei]

well, we know for for Progressive. Thank you, It really helps me.

[JDZYN]

Say I'm using Easy 5 for a ~900px preview size render.
Would it be appropriate to estimate ~4x longer for a 3800px render? Or am I over looking something?

[JDZYN]

Say I'm using Easy 5 for a ~900px preview size render.
Would it be appropriate to estimate ~4x longer for a 3800px render? Or am I over looking something?

I think I am overlooking something... we're considering "area to be rendered"
So it would be about 16x longer? (!?!?!?)

889,249px in 943x943 image "A"
14,440,000px in 3800x3800 image "B"

B/A = 16.23842140952647

so a 2h21m render upsized would take ~38h17m !?!?

Guess i'll be using Easy 3 for the final. :/

[Fletch]

This is not linear - so a finish time for your rendering can not be extrapolated, or intelligently calculated or guessed, by knowing the render time for a lower resolution and lower render setting, as far as I am aware.

...
Due to AA time being a complete wildcard it is basically impossible to predict render times for Easy 1-7 as far as I'm aware.

...
No, knowing the AA time for a low render setting can not ( I don't believe) help extrapolate the render time for "High"...