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Distant light angle leads to fireflies

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Distant light angle leads to fireflies

Unread postby machieb » Tue May 10, 2022 11:09 am

Hello,

I have the problem, when I increase the distant light angle to get softer shadows, fireflies appear.
I attach two screenshots where you can see the fireflies with light angle 2 and no fireflies with light angle 0.
What can I do to get a softer shadow without fireflies?

Thanks Marcus
Attachments
Clarisse_fireflies_sunlight_angle_02.jpg
Angle 0
Clarisse_fireflies_sunlight_angle_01.jpg
Angle 2
Last edited by machieb on Tue May 10, 2022 5:37 pm, edited 1 time in total.
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Re: Distant light angle leads to fireflies

Unread postby machieb » Tue May 10, 2022 12:45 pm

It seems that the higher I set the light angle the bigger gets the distant light shape in the reflection.
One solution might be to set the "Reflections Max Depth" of the distant light to 0. So the distant light is not reflected. So I have no fireflies and I can set the angle as high as I want. But I loose some of the smaller reflections...
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Re: Distant light angle leads to fireflies

Unread postby sam » Tue May 10, 2022 4:10 pm

mmmh I'm sorry but where exactly do you see fireflies? What I see is the specular highlight of the sun on the car bodies. This makes sense since the bigger the sun (increasing the angle) the bigger its surface on the reflective surface.

I'm not sure to understand the problem here. The first image looks wrong (because of the lack of specular highlight since the angle is 0) and the second image looks more realistic.
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Re: Distant light angle leads to fireflies

Unread postby machieb » Tue May 10, 2022 5:23 pm

Thanks Sam for your reply.
You are right the second image looks more natural because of the sun reflection in the car bodies.
But the pixel are too bright and look like fireflies in an animation.
My solution was: I created two sunlights with the same alignment, one that is driving the shadows, transmission and diffuse (setting the reflection max depth to 0).
The other light is driving only the sun visible in the reflections (setting the diffuse max depth, transmissions max depth and shadow max depth to 0). So I can control the shadow softness (with Angle) on light one.
On light two with Angle I control the size of the reflection.
The brightness of the sun reflection in the carpaint I control via exposure and intensity.
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Re: Distant light angle leads to fireflies

Unread postby sam » Tue May 10, 2022 10:50 pm

Ok but just so you know, these are not fireflies.
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Re: Distant light angle leads to fireflies

Unread postby esmith » Thu May 12, 2022 5:31 pm

you will never ever be able to call out a "firefly" in a render of that low refinement and/or resolution. As Sam said, it's just the reflection of the larger "sun". What you have done is a way, if you want to separate what you see reflected from what is causing the reflection. Which by definition is breaking reality, which is fine if it gets you the result.
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