Depth of Field

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peter_greger
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Joined: Mon Apr 26, 2021 7:48 am

Depth of Field

Post by peter_greger » Mon Apr 26, 2021 8:17 am

Hi!

I am currently working on a paper where i compare different render-engines (LuxCore, Arnold, Renderman and Cycles). I have the same scene set up and rendered through the different engines, what really surprised me is how much they differ when it comes to depth of field. The amount and the appearance of the blur is vastly different between the images even though the factors are the same (aperture size, focus distance etc.). So my question is basically, does anyone know why this is? How does LuxCore calculate depth of field? Any help or guidance would be greatly appreciated!

CodeHD
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Re: Depth of Field

Post by CodeHD » Mon Apr 26, 2021 10:24 pm

Hi,

it might help a bit to judge this better if you show some exact comparison, because settings might have something to do with it.

I can think of one example of this that has come up before (that you did not explicitly mention): Scene scale. With LuxCore, all yur objects have to be set up in units of meters size for the DOF settings to have the correct effect. I kind of doubt that this will explain your observation, however, because if anything it will make a difference of a factor of 10 or more.

LuxCore calculates it by originating the rays not at a point-camera, but from within a circle correspoding to the aperture size.

kintuX
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Re: Depth of Field

Post by kintuX » Mon Apr 26, 2021 11:06 pm

Along different apps using different units, what engines do under the hood is basically developer's choice and you'll have to ask them specifically about paths they took.
Also note you'll have it a bit hard to go in depths with Arnold and might be better to focus on open source engines. At least consider adding appleseed & mitsuba2 to comparison. As are quite fairly studied and well known w/ academia.
But fundamentally, first construct a real scene and get imagery for reference (a must have).

peter_greger
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Re: Depth of Field

Post by peter_greger » Wed Apr 28, 2021 12:52 pm

compare_renders_renderman_cycles_luxcore_photo.png
CodeHD wrote:
Mon Apr 26, 2021 10:24 pm
Hi,

it might help a bit to judge this better if you show some exact comparison, because settings might have something to do with it.

I can think of one example of this that has come up before (that you did not explicitly mention): Scene scale. With LuxCore, all yur objects have to be set up in units of meters size for the DOF settings to have the correct effect. I kind of doubt that this will explain your observation, however, because if anything it will make a difference of a factor of 10 or more.

LuxCore calculates it by originating the rays not at a point-camera, but from within a circle correspoding to the aperture size.
Scene scale is the same in all scenes. The settings for the camera (and lens) are all set to the same as the camera we used to take the real photo. LuxCore does indeed originate the rays from a perfect circle as opposed to renderman, Arnold and cycles that use the shape of an aperture with a certain amount of aperture blades (in our case 7). But I assume this is not the only difference between the renderers when it comes to depth of field since none of them have the same look, even the ones that have the same amount of aperture blades.
kintuX wrote:
Mon Apr 26, 2021 11:06 pm
Along different apps using different units, what engines do under the hood is basically developer's choice and you'll have to ask them specifically about paths they took.
Also note you'll have it a bit hard to go in depths with Arnold and might be better to focus on open source engines. At least consider adding appleseed & mitsuba2 to comparison. As are quite fairly studied and well known w/ academia.
But fundamentally, first construct a real scene and get imagery for reference (a must have).
Yes, this is exactly what we did, and the results show that there is a clear difference between the images when it comes to depth of field depending on what renderer was used :) Believe it or not but one of the guys at Arnold was actually the first to respond! Now we just need to figure out how the other renderers do it.

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Dade
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Re: Depth of Field

Post by Dade » Wed Apr 28, 2021 1:35 pm

peter_greger wrote:
Wed Apr 28, 2021 12:52 pm
LuxCore does indeed originate the rays from a perfect circle as opposed to renderman, Arnold and cycles that use the shape of an aperture with a certain amount of aperture blades (in our case 7).
No circular shape is named bokeh distribution in LuxCore and it is supported in v2.5: https://luxcorerender.org/new-features-in-v2-5/

The distribution inside the bokeh shape has a huge impact on how DoF looks and it may explain the differences you are observing (this kind of parameters are fully configurable in LuxCore but you have to look in bokeh configuration).
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peter_greger
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Re: Depth of Field

Post by peter_greger » Wed Apr 28, 2021 2:27 pm

Dade wrote:
Wed Apr 28, 2021 1:35 pm
peter_greger wrote:
Wed Apr 28, 2021 12:52 pm
LuxCore does indeed originate the rays from a perfect circle as opposed to renderman, Arnold and cycles that use the shape of an aperture with a certain amount of aperture blades (in our case 7).
No circular shape is named bokeh distribution in LuxCore and it is supported in v2.5: https://luxcorerender.org/new-features-in-v2-5/

The distribution inside the bokeh shape has a huge impact on how DoF looks and it may explain the differences you are observing (this kind of parameters are fully configurable in LuxCore but you have to look in bokeh configuration).
Thank you kindly for your response! :) It definitely clears things up a bit more!
My bad, I should have clarified, the image vas rendered using LuxCore 2.4
Exited about the new features though!

JulianoLisboa
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Re: Depth of Field

Post by JulianoLisboa » Wed Apr 28, 2021 2:35 pm

Can you put the site where the article link will be?

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