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B_Free
01-16-2014, 04:22 PM
Hi All,

I'm having trouble with the edge of the Sun in my render below. Behind the Sun I've got a light creating a lens flare. Most of the time the setup looks fine, but when the Earth starts to pass behind the Sun, there's a line where the lens flare disappears.

Any ideas how I can easily fix this? I've included my node setup that creates the Sun's transparent edge.
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prometheus
01-16-2014, 04:56 PM
Hi All,

I'm having trouble with the edge of the Sun in my render below. Behind the Sun I've got a light creating a lens flare. Most of the time the setup looks fine, but when the Earth starts to pass behind the Sun, there's a line where the lens flare disappears.

Any ideas how I can easily fix this? I've included my node setup that creates the Sun's transparent edge.
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without the lensflare, does it still give the sharp edge? just to make sure if it has to do with the lensflare or simply that you need to work on the edge transparendy?
also, why do you have edge transparency on the sun at all?
why donīt you just remove that and work with a glow filter instead, or add a huge null with hypervoxels for some sunglow and even small flare look.

michael

B_Free
01-16-2014, 09:28 PM
Hi Prometheus, Thanks for the ideas! But I think the problem is a combination of the edge transparency and the lens flare, because without the flare it looks just fine.
Here's how it looks with no lens flare:
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I tried rendering a glow around the Sun (but still using the same transparent edge surface), and the result wasn't any better.
Here it is with glow added, but no lens flare:
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As for why use the edge transparency at all, in real life the edges of the Sun are less bright than the center it's called Limb Darkening (Here's the wikipedia page (http://en.wikipedia.org/wiki/Limb_darkening).) An edge transparency creates those nice, soft edges for the Sun instead of having to monkey around with glow brightness and things.

prometheus
01-16-2014, 10:25 PM
Hi Prometheus, Thanks for the ideas! But I think the problem is a combination of the edge transparency and the lens flare, because without the flare it looks just fine.
Here's how it looks with no lens flare:
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I tried rendering a glow around the Sun (but still using the same transparent edge surface), and the result wasn't any better.
Here it is with glow added, but no lens flare:
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As for why use the edge transparency at all, in real life the edges of the Sun are less bright than the center it's called Limb Darkening (Here's the wikipedia page (http://en.wikipedia.org/wiki/Limb_darkening).) An edge transparency creates those nice, soft edges for the Sun instead of having to monkey around with glow brightness and things.

uhhm...not sure I would go that way anyway with edge transparency, but I need to check that more carefully aboout limb darkening and what you mean.
But...youré attachments are invalid, so we canīt see the sun actually.

prometheus
01-16-2014, 11:03 PM
Ahh...checking the limb darkening, but you know if we are talking in real life, the sun doesnīt have any transparency edges, skip that.
what you should do for that look, use incidence gradient on the luminosity channel instead, and from that image, I donīt see any soft edges, the look of it is just darker at the edges.
If you persist with transparency, you might wanīt to try the shaders tab and the surface shader instead, edge transparency and in transparency mode, but I would skip it and use incidence angle and maybe a glow to soften it, for direct feedback, actually throw in hv sprite.


Edit..there is a small appaerence of soft edged indeed, when zooming in very close to it, have to check what could be best.

Michael

prometheus
01-16-2014, 11:19 PM
look no nodes:)
just the shader, be very careful using the edge threshold, between 0,20-0,23

anyway, I donīt think it look realistic or cool with lensflare so prominent and so big eminating from the sun itself, if you were to look in space from shots of nasa, I dont recall seeing any of those, and for scifi shots it would
look better with corona glow, of hvs as I mentioned and only slightly lensflare streaks around the sun, star filter I would turn of unless it isnīt just to be a very distant sun or star.

see image, you need incidence gradient on the luminosity too.
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If you persist with your scene and the node transparency, you might want to turn of some shadow settings,maybe turn off the raytrace shadows for the flare.
or maybe turn of raytrace transparency in the render panel..not sure about that though, or in the lights/object panel..exclude the sun object from the light.
Michael

spherical
01-17-2014, 02:56 AM
Prometheus is on the right track. First, you need to understand why Limb Darkening happens. Limb Darkening is, well, limb darkening. It doesn't have much at all to do with transparency or lack thereof. It has to do with what is essentially looking deep into the ball of boiling gas that has deep fissures that reveal levels farther beneath the surface. Those inner levels of the Photosphere are brighter because they are closer to where the fusion reaction that is converting hydrogen into helium and heavier elements is running. When looking radially into this spiky sphere, more illumination will be apparent than when looking at it from the side. The limbs are tangent to the look angle and will be darkest. Why? Because the surface is coolest. All you cans see of a spiky structure from the side are the top ends. While there will be transparency between prominences that jut out into space, the essential contiguous sphere does not have any significant amount more transparency at its limb than it does at its center. It's just not as bright.

B_Free
01-17-2014, 12:17 PM
Sorry the attachments failed. Here they are again...
Here's how it looks with edge transparency, but no lens flare:
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Here it is with glow added, edge transparency, but no lens flare:
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I've been trying your suggestion to use hypervoxels instead of lens flare to create the glow, but I'm afraid that's working even worse for me...
Here it is still with edge transparency and hypervoxels flare: (Note the HV null was in front of the Sun for this render.)
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I also tried removing the edge transparency, but it still looks a little funny along the edge of the Sun in front of Earth.
Here it is with no edge transparency, but back with lens flare from light:
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I need to get this done today for my client, so I'm probably going to go with the last one since it looks the best. (Btw, the client already approved the look of the Sun so that's another reason I don't want to make drastic changes to it.) If you have any other ideas please keep shooting them my way. Thank you all very much for your help!!!

spherical
01-17-2014, 04:13 PM
The last one looks pretty good. I'd suggest getting some mottled texture in the star surface if you can. Having it be homogenous doesn't convey as much about it being spherical and not a 2D disk. This will be another opportunity to cement the Limb Darkening, as the mottled texture can/should have its own darkening effect.

prometheus
01-17-2014, 04:40 PM
hereīs some oldies I did quite some time ago...


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some native procedural texturing, hv..for flares, and one image with displaced geometry and hvīs on vertices for testing protuberans flares.
Thereīs also a free sun,planet shader, (simbiont) wich gives a nice texture, also shown in some of the images here.

spherical
01-17-2014, 04:57 PM
That HV Prominence is pretty cool (actually hot, but you know what I mean). :)