Sun's intensity

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Egert_Kanep
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Sun's intensity

Post by Egert_Kanep » Mon Aug 27, 2018 10:42 am

What is the correct intensity for sun? In real life sun's intensity is constant, is it not?

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SATtva
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Re: Sun's intensity

Post by SATtva » Mon Aug 27, 2018 11:38 am

The amount of light emitted by the Sun is roughly constant (although it's affected by the amount of sunspots and the Sun activity in general). The amount of light received at the ground is far from constant -- it's greatly affected by the atmospheric conditions.

For a normal clear sky conditions the intensity value should be 1.

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Egert_Kanep
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Re: Sun's intensity

Post by Egert_Kanep » Mon Aug 27, 2018 12:42 pm

Okay, so when I leave sun's intensity at 1, it should correspond to the intensity that we see with clear sky on earth? I'll give this a try

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Re: Sun's intensity

Post by Sharlybg » Mon Aug 27, 2018 12:53 pm

For a normal clear sky conditions the intensity value should be 1.
Gain "1" in luxcore i suppose ?

And luxcore sun gain 1 = 110k lux.

https://en.wikipedia.org/wiki/Daylight
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Egert_Kanep
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Re: Sun's intensity

Post by Egert_Kanep » Mon Aug 27, 2018 1:02 pm

Simple test scene for sun light. My camera has 5.6 aperture, 1/500 shutter speed and 100 iso. If I need to use lower shutter speed, let's say 1/50, picture gets too bright. In real life we have neutral density filters to darken the image. What would be the correct way to do it in LuxCore. I know I can turn iso down to 10 or 1, but with real life cameras, I think we cannot go to so low iso values.
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kintuX
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Re: Sun's intensity

Post by kintuX » Mon Aug 27, 2018 2:43 pm

Egert_Kanep wrote:
Mon Aug 27, 2018 1:02 pm
Simple test scene for sun light. My camera has 5.6 aperture, 1/500 shutter speed and 100 iso. If I need to use lower shutter speed, let's say 1/50, picture gets too bright. In real life we have neutral density filters to darken the image. What would be the correct way to do it in LuxCore. I know I can turn iso down to 10 or 1, but with real life cameras, I think we cannot go to so low iso values.
a.) use smaller Aperture (Camera)
b.) lower Exposure (Color Management)
c.) create ND filter (Mesh&Material)
NDfilter.jpg

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Re: Sun's intensity

Post by B.Y.O.B. » Mon Aug 27, 2018 2:54 pm

Egert_Kanep wrote:
Mon Aug 27, 2018 1:02 pm
In real life we have neutral density filters to darken the image. What would be the correct way to do it in LuxCore.
Just alter one of the tonemappers multipliers (aperture, shutter speed or ISO sensitivity) so the image gets darker.
I think ND filters usually specify how many stops they are darkening, so you can just subtract that number from the corresponding multiplier.
It doesn't matter which one you pick.
c.) create ND filter (Mesh&Material)
This will degrade rendering performance and is not really necessary.

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Re: Sun's intensity

Post by Sharlybg » Mon Aug 27, 2018 3:03 pm

If it is for Architecturale interior rendering i propose you to try theses tips if you have time.

Some general workflow tips to render faster interior:

. Tone mapp linear 1 / auto disable

. Sky + sun (make sure they are not linked for easy tune) instead of HDRi (Most of the time HDRi requiert more computational power)

. Use shader Albedo below 0.8

. with sun power >>> 0.0001 / sky 0.0002 you can use a clamp value of 10.

. Sobol + Log power


. Denoiser settings :

Try theses one :

HDT >>>> 0.7

SW >>>>> 8

Scales >>> 4

PR >>>>>> 1

. Switch to Path Ocl and adaptive sampling to 0.95

. Switch to Filmic
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Egert_Kanep
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Re: Sun's intensity

Post by Egert_Kanep » Mon Aug 27, 2018 3:59 pm

Interesting ideas here. At first I discarded changing aperture, because I thought I would lose my shallow dof. But dof is not linked to tonenapping :D

Is there any benefit with different tonemappings performancewise?

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Re: Sun's intensity

Post by B.Y.O.B. » Mon Aug 27, 2018 4:21 pm

Egert_Kanep wrote:
Mon Aug 27, 2018 3:59 pm
Is there any benefit with different tonemappings performancewise?
I don't think so.
Tonemapping is only computed when the image is updated, and it is a very fast operation. Also, it's accelerated with OpenCL in LuxCore.
It does not matter for rendering performance which tonemapper you choose.

By the way, I hope it's clear that tonemapping does not perform any "camera simulation" or so.
The "camera settings" tonemapper type is only useful if you have footage from a real camera and want to match it with LuxCore.
You could just as well compute the necessary multiplier by hand and put it into the linear tonemapper.

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