Rainbow Test

[Simius Strabus]

There was no shortage of rain yesterday and when the setting sun came out there was a huge rainbow. (sorry, no photo taken...)
So now I'm trying to create a rainbow in TG2. Getting there step by step.
It's a tiny unseen planet without an atmosphere node and six cloud layers, one for each color.
Added a camera at the center of the tiny planet and two distance shaders to get only a thin 'slice' of the cloud layer.

[cyphyr]

Very nicely done. There was some work done on rainbows a couple of years back, if you haven't done so already check out BigBen's thread on the subject.
Cheers
Richard

[inkydigit]

ahh, the elusive rainbow...very nicely done indeed!

[Kadri]

Look good Simius 

[Tangled-Universe]

Very nice! Maybe the transition between colour-bands could use some work, but so far it looks pretty convincing to me.

Very nicely done. There was some work done on rainbows a couple of years back, if you haven't done so already check out BigBen's thread on the subject.
Cheers
Richard

I remember that thread too, makes me wonder how geeky we must be

Anyway, his method was very complicated and slow if I recall correctly and I'm very surprised to see this solution here which is straight-forward and probably quite fast as well.
He probably could speed it up a tad bit by making the cloud localized, although I'm not 100% sure how a localized cloud's texture space works combined with the texture space of distance shader.

To explain for others: a localized cloud renders faster because the fractal noise input only needs to be calculated for the localized area and not for the complete texture/image space. If you 'isolate' a cloud using a distance shader then still the complete texture/image space needs to be calculated and thus it is slower. However, how does this work when it is combined? Interesting perhaps to test some time.

[Simius Strabus]

Right now I'm in the process of making the transition between layers smoother. Inverting the profile and setting the base softness to 1 is helping a lot. Also, adding a cloud layer with a neutral color that covers the whole rainbow is promising.

[TheBadger]

very interesting, and very complicated. Good start!

[Simius Strabus]

Made this one with the settings as described earlier. Getting there....

Rendered it at 720x1440 for a friends iPhone case-cover.

[Simius Strabus]

Just another test render here.

[Kadri]

Looks better 

[Oshyan]

Shockingly nice looking! Good to see a simpler approach to this is working well.

- Oshyan

[Lady of the Lake]

Very nice.   Way beyond my learning curve, but maybe someday. 

[blackcat]

I certainly admire all the effort being put into creating a rainbow entirely within TG, and I can see how it might be satisfying as an intellectual exercise...but wouldn't be infinitely easier and faster to simply add one (via Photoshop for instance) as a post-rendering effect?

[cyphyr]

In many cases it would but there are plenty situations (mostly animation) where having the effect "in scene" can make life so much easier.
Richard

[blackcat]

In many cases it would but there are plenty situations (mostly animation) where having the effect "in scene" can make life so much easier.
Richard

True enough.

Nevertheless, in the case of a rainbow (considering how one is actually generated in nature), I would think that even in an animated sequence it would be both easier and more realistic to do it as a separate element.