Progressive vs buckets, render time difference

[maru]

Again, I'm not sure if it's a bug. Rendered the same region with two setups:

1. Progressive, PTS: 100, passes: 4

2. Bucket, PTS: 100, initial samples: 4


If I understand it correctly, for path tracing this would mean 100 rays per pixel x 4 passes = total 400 samples.
And for buckets, 100 rays sampled 4 times for each pixel = total 400 samples.

I thought the image should look the same and render with same speed. It looks exactly the same, but rendering time is much longer.

[Ondra]

you set adaptive steps to 0, right?

[maru]

What is adaptive steps?

[maru]

Another one. Progressive: 400 pts x 1 pass. Bucket: 400 pts x 1 initial sample.

btw, it's  Sep  3 2013 00:00:50

[Ondra]

just printscreen the settings ;)

[maru]

here you go

[Ondra]

ok, you are comparing something entirely different (adaptive buckets to nonadaptive progressive rendering), so the comparison makes no sense. There is no reason for the two times to be the same

[maru]

How is this adaptive for buckets if there is only one pass?

And if so, then why these two images look the same in terms of quality?

[Ondra]

you have "passes" set to 10. I've just tried with 1 and it works as expected. Just send the scene ;)

[maru]

I have passes set to 10 but completing 1/4 of the first pass took much longer than rendering the whole region in progressive mode. I can upload simplified version of this scene later.

[Ondra]

do it

[maru]

Ok, looks like HD cache is the cause of this. Without HD cache both images render with exactly the same time. After enabling HD cache, progressive rendering becomes faster and bucket rendering becomes significantly slower.

I added those objects around lights to make the lighting less "uniform" but it also works with regular lights.

[rafpug]

Hi maru

I tried the scene while maintaining your configuration
the final image I will be too bright

It 's normal?

[cecofuli]

Mmm.. interesting test!
 In fact, usually I prefer bucket (better quality and little adaptive sampling) and I found Bucket mode slow.

[maru]

Hi maru

I tried the scene while maintaining your configuration
the final image I will be too bright

It 's normal?

If you didn't change any settings, this means you have wrong gamma configuration in Max.

In fact, usually I prefer bucket (better quality and little adaptive sampling) and I found Bucket mode slow.

Yes, in theory adaptive buckets MUST be more efficient than non-adaptive progressive rendering. But it looks like there is some bug with HD cache which is affects rendering speed in more complex scenes. It's exceptionally visible when you're rendering something for school on a cheap laptop and after whole night you end up with noisy images. ;)