Author Topic: number of passes in crop area  (Read 2465 times)

2016-03-12, 01:07:08

fco3d

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Hi, maybe a dum question, but I wonder.
I always have hard time estimating how many passes I need to get a clean image, so I was wondering if I do a crop rendering of the scene and I get the number the passes that it take to clean up it will apply the same for the full size image?? Of course time wise will be more but the number of passes should be the same ?? or the passes are pixel dependent?
Thank you.

2016-03-12, 02:18:05
Reply #1

SairesArt

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Hi, maybe a dum question, but I wonder.
I always have hard time estimating how many passes I need to get a clean image, so I was wondering if I do a crop rendering of the scene and I get the number the passes that it take to clean up it will apply the same for the full size image?? Of course time wise will be more but the number of passes should be the same ?? or the passes are pixel dependent?
Thank you.
Simplyfied:
Passes = anti aliasing
Theother two variables, that determine image quality have the passes as a multiplier.
Rays for GI (AAvsGI slider) and the direct light rays, responsible for soft shadow detail (light sample multiplier)
So it seems passes = image quality, but that is not simply the case.
Simple geometry does not need more than 20 passes - ever (provided there is no dof and moblur) but needs the same amount of GIrays like any other scene.
So what you do with simple geometry is apply a higher AAvsGI, so you cover the same amount of rays in the 20 passes needed to clean up the edges, like you would compared to 70 passes default settings.
When you have carpets, high detail displacements, depth of field or motion blur, you need more passes maybe 100+.

Default settings are very well chosen.
But since you Start to dwell into optimi├čation and "how many passes do I need" you might wanna understand what a pass is.
So a kitchen never needs more than 25 passes usually, but needs A Crap Ton of GI rays, so you don't wanna waste computation power sampling over and over again that simply table edge a million times.

The question stops being " how many passes do I need" and becomes "how much time will it take me to clear the.image, while not wasting power on samplin stuff unnecessarily"

Corona Freshdesk with more details to read
https://coronarenderer.freshdesk.com/support/solutions/articles/5000518064-how-many-passes-is-enough-

2016-03-12, 09:18:07
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romullus

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[..] so I was wondering if I do a crop rendering of the scene and I get the number the passes that it take to clean up it will apply the same for the full size image?? [..]

Yes, that's exactly how it works... at least up to v1.3. However in upcoming v1.4 with the introduction of adaptivity, this might not be true anymore, but i'm not very sure about that yet.
I'm not Corona Team member. Everything i say, is my personal opinion only.

2016-03-15, 22:07:01
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fco3d

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Thank guys for your answer.


Fco.

2016-03-16, 01:14:12
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3dbybrunolopes

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That's a nice and simplified explanation,

So can you tell us what can be a realistic number of GIvsAA and Light samples, As a example?
Senior 3D Artist and Technical Director

2016-03-16, 01:54:01
Reply #5

SairesArt

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That's a nice and simplified explanation,

So can you tell us what can be a realistic number of GIvsAA and Light samples, As a example?
Unless you have soft shadows or low angle sun, you can leave LSM at 1, although you need higher LSM if you have Volumes.
2 is a conservative default value.

If you happen to do animation with simple geometry like me,  no high IOR refractifity is used and don't have dof or moblur, then 8 passes is already enough, but GI after 8 passes is aweful, so you need to compensate with 64 or 80 AAvsGI.

If you have Carpets, displacements, dof, moblur, then you need more passes and default settings (with LSM 1) do already a great job. So you don't need crazy high GI sampling and there is no reason to go higher then 16.

As you see it is very dependant on what the scene is or what you need.

Refractivity, fine geo, dof, moblur, bad Antialiasing, fireflies from reflectivity combined with detailed normal and bump maps etc... Need many passes
Soft shadows, volumes with much direct light, god rays, low angle sun, Noise in the Direct lighting pass etc... Need more direct light samples, so more LSM
Noise in indirect pass and GI noise, SSS noise, etc... Need more rays casted, so higher AAvsGI

Find out what you scene needs the most and just crush everything else to the bare minimum, without loss in quality after the image has rendered.

But then again we are talking optimisation here, you can just say screw it, corona with adaptivity will manage and let it render on default settings, which are in the golden center of all use cases and adaptivity will do its thing.