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General => Terragen Discussion => Topic started by: groverwa on February 21, 2007, 08:39:00 PM

Title: Shaft of light
Post by: groverwa on February 21, 2007, 08:39:00 PM
Gday

Does anyone know how to make a shaft of light come out of the clouds and go down to the ground/ water after the sun has set?

I have only seen this a few times and it is quite spooky - If I was around in the days that Stone Henge was built it would have had a great effect on me

Mike
Title: Re: Shaft of light
Post by: gradient on February 21, 2007, 11:44:14 PM
I think it's called a Sun Pillar....here's link to explain it;

http://www.atoptics.co.uk/halo/pillar.htm (http://www.atoptics.co.uk/halo/pillar.htm)

Haven't played with TG2 much lately...so...can't help on the how to!
Title: Re: Shaft of light
Post by: dhavalmistry on February 21, 2007, 11:50:44 PM
here it says...

"Pillars are not actually vertical rays, they are instead the collective glints of millions of ice crystals."
Title: Re: Shaft of light
Post by: sonshine777 on February 22, 2007, 01:10:15 AM
Looks kind of like the "Bliss effect" that can be achived with 9.xx I don't know if anyone has done it in TG2. :)
Title: Re: Shaft of light
Post by: groverwa on February 22, 2007, 02:03:12 AM
Gday

Thanks for the comments - I should have explained with a diagram - see the attached doc

Mike
Title: Re: Shaft of light
Post by: dhavalmistry on February 22, 2007, 02:24:01 AM
I havent seen that being done in TG2 yet!

I am not expert in all this but I think it will only happen if the sun is around 2 degrees or below
Title: Re: Shaft of light
Post by: Mohawk20 on February 22, 2007, 11:34:19 AM
Perhaps an additonal light inside the clouds would help to simulate this...
Title: Re: Shaft of light
Post by: Oshyan on February 23, 2007, 06:41:15 PM
I've never seen anything like that and would be surprised if a cloud could reflect enough light to see an actual shaft or ray *after* the sun has gone down. I'd be very interested in some documentation or info about this phenomenon though as I know there are lots of interesting and unusual atmospheric effects out there.

As far as simulating it in TG2 goes I do think you'd need to use an additional light source and it would probably be quite tricky to get it placed right and all setup properly.

- Oshyan
Title: Re: Shaft of light
Post by: groverwa on February 23, 2007, 06:49:41 PM
Gday Oshyan

Thanks for your answer - like I said I have only seen it a few times and it is very spooky - I asked the Australian Meteorolog and recd this answer: -

"A property of atmospheric optics is that cloud droplets can reflect sunlight similar to a mirror. The reflection of sunlight off clouds occurs in a similar way to your diagram, except that the angle of incidence equals the angle of reflection, so that the reflected shaft of light cannot come directly down at right angles to the ground. There are many pictures of this phenomena on the web if you do a search, including an explanation of the physics, eg http://cimss.ssec.wisc.edu/wxwise/class/optics.html."

When I find some pics I will post them

Mike
Title: Re: Shaft of light
Post by: Oshyan on February 23, 2007, 07:43:31 PM
Ah, thanks for the additional info. This makes reasonable sense, although it's still surprising that the light itself would be visible. I guess under very specific conditions... It sounds like it would be amazing! http://www.atoptics.co.uk/ is a great site for photos of unusual atmospheric phenomona, but it seems to be down right now. I don't recall seeing the one you mentioned there, unfortunately.

- Oshyan
Title: Re: Shaft of light
Post by: Will on February 23, 2007, 07:45:26 PM
links broken
Title: Re: Shaft of light
Post by: old_blaggard on February 23, 2007, 08:41:21 PM
Works now.  As Oshyan said, the site was probably down for a while.
Title: Re: Shaft of light
Post by: gradient on February 23, 2007, 11:24:15 PM
Folks...the sun pillar is at the link I gave before....seek ( read)  and ye shall find....

http://www.atoptics.co.uk/halo/pillar.htm (http://www.atoptics.co.uk/halo/pillar.htm)

Actually, it is not that uncommon an occurance...I have seen it many times....
Title: Re: Shaft of light
Post by: Oshyan on February 24, 2007, 01:38:44 AM
Yeah, I've seen sun pillars a few times myself. But what groverwa was describing sounds quite different. There are actually examples of potentially similar things on the site I linked to though: http://www.atoptics.co.uk/halo/lpil.htm

- Oshyan
Title: Re: Shaft of light
Post by: gradient on February 24, 2007, 01:41:44 AM
Yes, there are several links to pillar types at that site....I think groverwa may be talking about a "lower" pillar which comes from the cloud and goes downward.