last passes take longer?

[Johnny]

I've been doing some high quality renders lately that take in the neighborhood of 24 to 50 hours to complete. I don't mind bcs the results are good, and I do not have the latest, greatest hardware.

but what I've noticed is that those last render passes seem to take much longer than the previous ones.

One image of mine was at pass 32 of 33, and had taken about 24 hours to get there, so I figured that I'd have my pic that evening, in an hour or so.

The render didn't actually finish until the wee hours, some 4 or 5 hours later than my guesstimate.

Does each render pass involve the same amount of calculations, or do the later ones take more calculations?

Or is there some other problem?

thanks!

J

[Captain Obvious]

Each pass should require about the same amount of calculations. It does vary, depending on what the rays actually hit, but it should be in the same ballpark.

[BeeVee]

That depends if you have adaptive sampling on. If you don't then eah pass should take roughly the same amount of time, if you do, then AS will continue until the AA is good enough by the standard you've given.

B
Edit: Hmm, that's tru for values of LW9 > 9.0... oops

[toby]

Do you have any post process filters, some of them don't apply themselves until after the final pass

[Johnny]

I don't believe so...I have shading noise reduction on, but that happens at the end of every pass.

I'm pretty sure that the same thing happens for each pass; just another pass at the image.


J

[ingo]

Could it be a memory problem, i have no clue how LW saves all the passes. Maybe you could render it again at a lower resolution. Otherwise all passes should take the same time, so i look at how long the first pass takes and multiply it with the number of passes and i got the exact rendering time.

[GaryLW]

I've had the same problem. Three quarters of the image was taking only twenty percent of the time. Until I realised I had reflection blurring on for the floor (duh!).