Why can't get specular reflections from the sun?

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Caronte
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Why can't get specular reflections from the sun?

Post by Caronte » Wed May 16, 2007 7:55 am

I have a scene with glass bottles, but Ican't see any specular on it from the sun :(

Any ideas?

P.D:
If illuminated with a Meshlight, the speculars are nice :?
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Sorry about my poor english ;)

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Kram1032
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Post by Kram1032 » Wed May 16, 2007 8:21 am

I see...
where is the sun (or where should it be)?

Try to make a much easier scene, where you shurely have to see sun

i.E. a cube, rendered from above, sun is directly pointing down on it --> glass mat ---> must give speculars.
then, also try a different camera angle...
It may be that.

I guess, either the angle of the camera, or that of the sun.

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Caronte
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Post by Caronte » Wed May 16, 2007 8:36 am

If you think on a real scene, the bottles sure have specular reflections on this sun angle at some place.
Anyway thi's not the probleme, because a meshlight far away on the same position as sun give nice speculars.
Sorry about my poor english ;)

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oodmb
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Post by oodmb » Wed May 16, 2007 12:11 pm

is the meshlight at the same angle as the sun? the specular you are seeing from the meshlight might be just reflections of the model, not actualy specular
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joegiampaoli
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Post by joegiampaoli » Wed May 16, 2007 12:38 pm

What I can mostly see in this example is that you will not see reflection from the sun, because you are (or the camera is) behind the bottles which are behind the sunlight, if you were the observor and was standing between the light and the bottles you might well then see the reflections.

EDIT: In other words you should place the camera on a similar angle than the light source...
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Iqwar
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Re: Why can't get specular reflections from the sun?

Post by Iqwar » Wed May 16, 2007 7:11 pm

Off Topic: Hi Caronte, I really love your Jack Blenderson image :P But where is he looking at? My friend told me, that he look like he is high a little bit ;-)




Sorry 4 my poor english :oops:

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Kram1032
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Post by Kram1032 » Wed May 16, 2007 11:48 pm

which jack blenderson?

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Caronte
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Re: Why can't get specular reflections from the sun?

Post by Caronte » Thu May 17, 2007 12:53 am

joegiampaoli wrote:In other words you should place the camera on a similar angle than the light source...
Thi's not the solution.
Iqwar wrote:Off Topic: Hi Caronte, I really love your Jack Blenderson image :P But where is he looking at? My friend told me, that he look like he is high a little bit ;-)
Yes, he is looking the cameraman hat :lol:
Kram1032 wrote:which jack blenderson?
He is talking about my latest work with Yafray (I'm learning Indigo now):
http://www.blender.org/features-gallery/gallery/images/
Sorry about my poor english ;)

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Kram1032
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Post by Kram1032 » Thu May 17, 2007 3:11 am

Ah^^
I saw it, but I didn't look at the title :D
great work :D

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manitwo
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Post by manitwo » Thu May 17, 2007 3:33 am

Disable bidir to get rid of the "sunlight/glass" issue, use hybrid=true to speed things up and set max_num_consec_rejections to "1000" and max_depth to "10000" to be sure the light reaches the cam.

btw: this is the cgtalk lighting challenge scene, right?

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Caronte
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Post by Caronte » Thu May 17, 2007 5:23 am

manitwo wrote:Disable bidir to get rid of the "sunlight/glass" issue, use hybrid=true to speed things up and set max_num_consec_rejections to "1000" and max_depth to "10000" to be sure the light reaches the cam.
Thanks by your help ;)

OK. I have now a nicer glass with nicer caustics, but the specular not appearing :(

I think the specularity is to much small so It's hard to see. If I use "Spec type=glossy transparent" (instead of "specular") and set the exponent to something like 1500, the speculars looks nice, but I lost the transparecy clear and get frosted glass :(

May be the sun is to much small?
manitwo wrote:btw: this is the cgtalk lighting challenge scene, right?
Yes, it's a good test for glass ;)
Sorry about my poor english ;)

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manitwo
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Post by manitwo » Thu May 17, 2007 6:18 am

Caronte wrote:May be the sun is to much small?
yes could be :roll:

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CTZn
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Post by CTZn » Thu May 17, 2007 12:34 pm

Like Joe I'm almost certain it's an angle issue, because actually there is a specular highlight in your image.
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Kram1032
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Post by Kram1032 » Thu May 17, 2007 4:10 pm

I dunno, really...
the sun is so big, that it's light comes nearly parallel.
so ther should be about the same specular effect in about the same angle...

that explanation of a too small sun, would be good:
in that case, yuo have to increase the resolution...

on a round shape, sunlight EVER will be squeezed, so maybe, the specular is about 1 pixel wide, or 0,5 or even smaller, so that supersampling finally completely get's rid of it... (even without SS, the specular wasn't there, as then, the most dominant colour is used, I guess...)

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CTZn
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Post by CTZn » Thu May 17, 2007 8:25 pm

the sun is so big, that it's light comes nearly parallel.
This is more likely to be caused by distance, but that's OT (again. Sorry).

Well I'm not certain as well, but due to the scene setup wich is ambiguous that can't be qualified as a bug IMHO. Furthermore I believe I can see highlights upon the bottles, mostly on their upper left side but I can't tell for sure; it's a blueish white, a spot where the sky reflection becomes lighter...

One way to check would be to apply some camera bloom or blades using Violet, it will reveal where highlights are.
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