sun edges?

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Pibuz
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sun edges?

Post by Pibuz » Sat Nov 14, 2009 10:21 pm

Sorry guys, I spotted it this morning when doing another test render for a tutorial.
Simply, the Sun has edges. I remember that this issue has been reported before, but I don't remember if it hadbeen fixed for the previous versions.
Btw, here are the images
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diffr_off_ISO_70.png
diffr_off_ISO_70.png (307.96 KiB) Viewed 3212 times
diffr_on_ISO_70.png
diffr_on_ISO_70.png (325.29 KiB) Viewed 3208 times
diffr_on_ISO10.png
diffr_on_ISO10.png (208.46 KiB) Viewed 3202 times

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psor
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Re: sun edges?

Post by psor » Sat Nov 14, 2009 10:30 pm

Sorry to say that but it's not a bug it's just an issue that pops up when using any sharpening filter.
Use a Gauss filter or better use AD instead which is more real anyway. ;)





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Re: sun edges?

Post by PureSpider » Sat Nov 14, 2009 10:57 pm

Or simply set your Super Sampling to 2 or higher :)

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psor
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Re: sun edges?

Post by psor » Sat Nov 14, 2009 11:11 pm

This won't help cause it's caused by downsampling and using Mitchell-Netravali as filter.


On the technical side, it's caused by float rounding errors and those lead to negative values
which are then clamped to zero (black). To lower the effect you can increase the bluring and
decrease the ringing. To avoid it, use a gauss filter instead and use a sharpening filter in post.


Anyway, using apperture defraction is much closer to reality and so just leave the filter as
it is and don't ya think to much about it. ;)






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Godzilla
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Re: sun edges?

Post by Godzilla » Sun Nov 15, 2009 3:27 am

I had the same problem with the lights in this scene. Where I turned the super sampling to 2 it fixed the issue, though.
samlavoie.xyz

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Pibuz
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Re: sun edges?

Post by Pibuz » Sun Nov 15, 2009 4:05 am

The supersample factor is already set to 2 and I'd strongly avoid to raise it, most of all because of the RAM consumption: it would work for a test scene like this, but could be a problem whith higher resolution renders.

BTW this stuff about sharpening and blurring and filters and stuff is way too complex for an average user, and - you have to agree with me - is quite tricky.
I suggest that Ono works a little more to find a way to eliminate the problem. Having the sun rendered correctly is a right for all.

Sorry Psor: I have to think about it. Perfectionist. :lol:

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psor
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Re: sun edges?

Post by psor » Sun Nov 15, 2009 12:44 pm

I've tried to render a scene myself. And ya, I've to say this has to be a bug. In the past this
scene was rendering fine, without the "shading" of the sun. And have a look the sun is able
to beam ... so beam me up Scotty! 8) :lol: :wink:


Image

click to enlarge




Nik, you really have to take a look at this. Mine is rendered with v2.2.7. I've rendered it with
supersampling set to 2 too, but the rendering above it's set to 1 to double check. I've tried
all filters and settings too, no change. The scene is attached to this post.









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ocean_TEST_01.pigs
Above scene as pigs.
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matsta
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Re: sun edges?

Post by matsta » Sun Nov 15, 2009 6:54 pm

I lol'd.

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mr_jo
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Re: sun edges?

Post by mr_jo » Mon Nov 16, 2009 9:13 am

I've done a similar scene test, Super Sampling set to 2, there's any edges on the sun but a strange shape (square) on the wall.
SkIndigo 2.2.3 and Indigo 2.2.1
Attachments
diffraction.jpg
diffraction.jpg (246.65 KiB) Viewed 2931 times
setting.jpg
setting.jpg (114.94 KiB) Viewed 2936 times

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OnoSendai
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Re: sun edges?

Post by OnoSendai » Fri Nov 20, 2009 1:53 pm

psor wrote:I've tried to render a scene myself. And ya, I've to say this has to be a bug. In the past this
scene was rendering fine, without the "shading" of the sun. And have a look the sun is able
to beam ... so beam me up Scotty! 8) :lol: :wink:
Hi Psor,
I think the problem with your model is that the sun is too close to the horizon, and the sky model is freaking out.

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OnoSendai
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Re: sun edges?

Post by OnoSendai » Fri Nov 20, 2009 1:54 pm

As a general answer to the dark edge around the sun, I would recommend using aperture diffraction, which should mean that the edge isn't visible.

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Re: sun edges?

Post by djegoo » Fri Nov 20, 2009 8:43 pm

mr_jo wrote:I've done a similar scene test, Super Sampling set to 2, there's any edges on the sun but a strange shape (square) on the wall.
SkIndigo 2.2.3 and Indigo 2.2.1
I ve already had that.
it is because your exposure is too high.
try reducing the sun power and increasaing the sky power, you will get almost the same result, without the square aperture.

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Pibuz
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Re: sun edges?

Post by Pibuz » Fri Nov 20, 2009 10:03 pm

OnoSendai wrote:As a general answer to the dark edge around the sun, I would recommend using aperture diffraction, which should mean that the edge isn't visible.
If you take a look to the top post you will see that the second image has aperture ON and still shows dark edges.
I also confirm mr_jo issue about "rectangular" diffraction even with circular shape enabled.

BTW I think you should find the problem and solve it, for it is often counter-productive to activate the diffraction while rendering, since diffraction uses loads of RAM so Indigo would probably crash... Activating diffraction doesn't SOLVE the problem, though: it is only a workaround. Maxwell renders the sun just fine, Fryrender either: why can't Indigo do just the same? I think Indigo deserves it :lol:

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Re: sun edges?

Post by Zom-B » Fri Nov 20, 2009 10:57 pm

Pibuz wrote:
OnoSendai wrote:BTW I think you should find the problem and solve it, for it is often counter-productive to activate the diffraction while rendering, since diffraction uses loads of RAM so Indigo would probably crash... Activating diffraction doesn't SOLVE the problem, though: it is only a workaround.
I think we're talking about physical diffraction, not the PostProcess Filter my friend :)
No Extra RAM cost and physical correct, a feature I would recommend to turn on always for final renders!!

Also check out your exported igs file, maybe your exporter just don't export the circular Aperture shape... mybe skindigo is the evil her...
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Pibuz
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Re: sun edges?

Post by Pibuz » Fri Nov 20, 2009 11:46 pm

Hi ZomB!
SkIndigo actually supports circular aperture..
ZomB wrote: I think we're talking about physical diffraction, not the PostProcess Filter my friend :)
No Extra RAM cost and physical correct, a feature I would recommend to turn on always for final renders!!
Can you make this clearer? I don't get you completely, sorry :!:
There is a way to have aperture on without using the post-process filter?

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