Natural rainbow

[DesignT]

Hi,

I am looking for your ideas about how to create a natural transparent rainbow.

I need to place the rainbow inside an arc (for example half o a donnut), can I cut the donnut at the midle and use it as a mask to show the rainbow.

What will be the best way to get it done ?

Thanks.

[Alfred]

Instead of creating a half-donut mask, apply a radial gradient fill directly to a half donut.

Rainbow.afdesign

[R C-R]

5 minutes ago, Alfred said:

Instead of creating a half-donut mask, apply a radial gradient fill directly to a half donut.

FWIW, I played around with that approach. It works fine as long as the aspect ratio of the donut remains unchanged, but stretching or shrinking it along one dimension ruins the effect because the radial fill does not remain true to the arc of the donut. If the aspect ratio needs to be changed, the donut probably has to be rasterized for that to work.

[Alfred]

32 minutes ago, R C-R said:

It works fine as long as the aspect ratio of the donut remains unchanged, but stretching or shrinking it along one dimension ruins the effect because the radial fill does not remain true to the arc of the donut.

A radial fill is clearly only going to work for a circular arc. If you want to stretch or shrink the arc, you’ll need to use an elliptical fill.

[DesignT]

Thanks for your suggestions but it does not seam natural and that will only work in in perfect arc.

Sorry I did not explain but I need to reproduce a natural rainbow arc, maybe I should try to make the rainbow inside a curve.

The color shift in nature seams much more progressive, is there any way to make it smooth ?

Please take a look in the file to see the kind of arcs that I am trying to do.

Thanks a lot.

 

 

Rainbow.afdesign

[GarryP]

Here’s a quick experiment that I threw together quickly.
You might be able to make something with it if you tweak various things.

rainbow.afdesign

[DesignT]

Hi GarryP

Unfortunately I can not open the file, I am getting "The file version is not supported by this version of Affinity."

Witch Affinity Designer version are you using ?

Update: I download the beta version and now  I can open the file.

Thanks GarryP that´s almost what I need, now instead of be over the background image, I will need to be a solid layer but the layer is cut (mask) in the area where we have the rainbow arc (ellipse) like it was a window in a format of a arc to see the rainbow behind the solid layer.

It´s a little difficult to explain.

Can you please send me a Version 6 file ?

Thanks

[gdenby]

Here's my offering. Its an eliptical gradient fill in donuts.

Rainbow.afdesign

[DesignT]

Thanks gdenby I will take a look.

[DesignT]

Hi gbenby,

Woowww that´s very cool,.....

How did you make the color decay in the bottom part of the ellipse ?

Thanks

[Alfred]

27 minutes ago, DesignT said:

How did you make the color decay in the bottom part of the ellipse ?

If you select either of the donut layers and switch to the Transparency Tool (wineglass) you’ll see that a linear transparency has been applied. I did something similar with my unnatural rainbow, but using an elliptical transparency set to affect both ends of the 180° arc.

[GarryP]

Oops, sorry DesignT. I use the beta without realising it these days.
It’s so stable that I don’t think about using the current commercial release.
gdenby’s file uses pretty much the same technique as my example – elliptical gradient etc. - so there’s not much point in me recreating mine in 1.6, but tell me if you really need it for some reason.

[gdenby]

32 minutes ago, Alfred said:

If you select either of the donut layers and switch to the Transparency Tool (wineglass) you’ll see that a linear transparency has been applied. I did something similar with my unnatural rainbow, but using an elliptical transparency set to affect both ends of the 180° arc.

What he said

[John Rostron]

I have to admit that when I saw a request for a "Natural Rainbow", I thought: why not go outside on a rainy day with the sun behind you?

A natural rainbow would always be a perfect arc by virtue of the way it is created. Anything else would be un-natural.

John

[R C-R]

FWIW, more than most people probably ever would want to know about rainbows & related optical phenomena can be found in the Wikipedia Rainbow article & its links.

[AffinityJules]

On the subject of natural rainbows.

A few years back I looked out of my window after a heavy, sudden rainfall, and saw this double rainbow. I dashed downstairs and took several photos - this being one of them.

[John Rostron]

This pic also illustrates a feature of natural rainbows. The background is darker to the outside of the inner rainbow and lighter to the outside of the outer rainbow. Again a consequence of the optics.

Double rainbows are commoner than you might think. 

John

[R C-R]

21 minutes ago, John Rostron said:

This pic also illustrates a feature of natural rainbows. The background is darker to the outside of the inner rainbow and lighter to the outside of the outer rainbow.

Also, both the primary & the fainter color-reversed secondary rainbows are brighter than the surrounding sky. Their apparent brightness can be affected by atmospheric water droplet size & shape variations (like where rain is falling in sheets) & even by impurities suspended or dissolved in the droplets, which can diminish the observed brightness of different spectral colors, most often the shortest wavelength ones visible near ultraviolet end of a rainbow's spectrum.

Considering all that & that digital camera sensors do not have the same sensitivity to different wavelengths of light as does our perception of them, getting a good photo of a rainbow as it appears to an observer on the scene, or creating an artificial simulation of one, is probably a lot more difficult that it might seem.

[DesignT]

8 hours ago, John Rostron said:

I have to admit that when I saw a request for a "Natural Rainbow", I thought: why not go outside on a rainy day with the sun behind you?

A natural rainbow would always be a perfect arc by virtue of the way it is created. Anything else would be un-natural.

John

When I say natural I mean that looks a real rainbow.

Sorry I disagree rainbow arc is almost of the time a not complete arc and as AffinityJules show there are also that kind of rainbows, I also saw like those and many many other forms.

I need to archive this effect.

Instead of be over the background image, I will need to be a solid layer but the layer is cut (mask) in the area where we have the rainbow arc (ellipse) like if we see the the rainbow thru a arc mask.

I don´t want that the rainbow overlays the other layer I need the rainbow goes behind the foreground and pass thru an arc cut.

It´s enough to give me an Ideia of the technic that I should to get this effect.

Thanks you all

 

[firstdefence]

A few years ago I saw an upside-down rainbow, they are called circumzenithal arcs, I was laying on some cedar decking I'd just put down, was pretty cool but only lasted about 30 seconds.

[R C-R]

I have occasionally seen circular rainbows while looking out aircraft windows, & rainbows in mists created by fountains & garden hoses, but never an upside down one.

[Old Bruce]

1 hour ago, R C-R said:

I have occasionally seen circular rainbows while looking out aircraft windows, & rainbows in mists created by fountains & garden hoses, but never an upside down one.

Never been to Australia? Sorry, couldn't resist.

[DesignT]

Now your focus is in the `natural rainbows" and that´s fine I now we are impressed with this natural event.

My opinion is that all rainbows are different, is like if the have their own ID signature depending of the weather conditions.

Can you give me some tips about how can I get this effect ?

Instead of be over the background image, I will need to be a solid layer but the layer is cut (mask) in the area where we have the rainbow arc (ellipse) like if we see the the rainbow thru a arc mask.

I don´t want that the rainbow overlays the other layer I need the rainbow goes behind the foreground and pass thru an arc cut.

It´s enough to give me an Ideia of the technic that I should to get this effect.

Thanks you all

[Alfred]

15 hours ago, DesignT said:

Sorry I disagree rainbow arc is almost of the time a not complete arc

When is a rainbow ever not a complete arc?? 

[AffinityJules]

If you could get high enough then would see the rainbow as a circle.