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Chasing Rainbows

February 19, 2010
Fake Rainbow

Fake Rainbow with very blue sky and fake looking clouds

One of the features I like in Vue 3D is the ability to generate a rainbow within the software. In my commercial work, it’s become a popular request, and seeing that St. Patrick’s Day is coming up, I’m sure I’ll get one or two last minute inquiries for a rainbow over a field image. I haven’t gone so far yet as to place a pot of gold at the end. Maybe at a future date. Building rainbows can be quite the conundrum though, and decisions have to be made. Do you go for something that is obviously Fantasy, try and go for realistic, or do you compromise between the two?

I’ve done several stock images in the style of the “Tropical Fantasy Rainbow” like the one above. One that I did was similar to this but in a square format was used on a CD cover during the past year. While pretty, almost perfect, happy and uplifting, this is usually not the way rainbows occur in real life. The rainbow pretty much ends abruptly at the horizon, and that’s not the way things happen in nature. For casual snapshooters, in real life, it’s usually more like this:

Rainbow Photograph

Rainbow Photograph taken in a shopping center parking lot

When rainbows occur in nature, the sky is usually not blue and pristine (unless you live in Hawaii of course!). More often than not, there are storm remnants, awkward sky colors that range from yellow to green to dark ominous gray, and sometimes the rainbow will even look incomplete. I was inside the store here when the sudden, fast moving thunderstorm hit. From inside the store, it looked like night at the peak. When the rain stopped for a few moments I ran for the car, then grabbed the (at that time) crappy pocket cam and snapped this image. A minute later the downpour started up again. As you can see, my “real life” rainbow pic is sad and lackluster. Unless conditions are optimum, the casual snapshooter is usually left unsatisfied. Thank goodness for Vue 3D. I don’t have to go chasing rainbows now 😉

Fake Rainbow Spectral

Fake Rainbow with Spectral Atmosphere in Vue

So what to do to give some realism to our 3D tropical island? I went into the Vue 3D Spectral Atmospheres which more emulate those found in nature. But some problems in doing this. In striving for more realism as in a storm effect, my render time for a large image is increased significantly (to about 12 hours), and Vue’s spectral emulation of nature is almost true to a fault here. The dark, dreary, unpleasant color undertones echo a bit of reality, but the overall look of the image would for the most part be unpleasing to a commercial client.

Fake Rainbow 3

Fake Rainbow in a compromise Vue 3D render using light blue, a Spectral lighting model, and some realistic clouds.

So let’s bridge the gap and strive for something that will be a little more pleasant and desirable than our original Fakey Version at the top of the post. In the modified image above, I’ve kept Vue’s Spectral Atmosphere mode, but lightened up the cloud cover significantly, and shifted the ambient sky more towards the fantasy blue. My results are pleasing, and I think this one will be a keeper. My rainbow has some nice color scatter at the horizon, and I have some small but more realistic looking clouds than in my original try. And because my atmosphere is really lightened up as far as content, my render time for a large size image is now reduced from 12 hours to about 3 with this atmosphere setting compromise.

3D should be not entirely about getting an absolute clone of reality, but it should be about getting an image that you like.

About the Rainbow Effect in Vue – some newcomers to the program think that you click the button and the rainbow appears. Not so. For the rainbow to appear, you must have the sun effectively behind the camera and pointed at the horizon where you want the rainbow to appear. The angle of the sun will determine how high or low your rainbow appears in the image. You can use the image below as a reference (click image the image for a larger version).

Rainbow Setup in Vue 3D

Don’t forget, Vue tries to emulate nature’s light, and when you see a rainbow, the sun is in essence behind you. It will take just a tiny bit of fiddling to get things the way you want. Moving the camera in and out will also change will also affect the “apparent” size the the rainbow, but realize that when moving the camera in and out, you change the whole field of view as well.

Happy Rendering! 😉

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2 Comments
  1. Michael Brown permalink
    February 19, 2010 11:31 am

    The end result looks great IMO. Very realistic.

  2. February 19, 2010 12:52 pm

    Thanks! I rendered up the large version and it looks great. Just going to do some minor color balancing in the foliage which will take just a few short minutes and it will be done.

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