A rainbow in Vue d'Esprit

The atmosphere is one of the most important aspects of a scene.
Thanks to the Atmosphere Editor, we have control over a lot of parameters, one of them being the rainbow.
In Vue you can add a rainbow automatically, just like a regular atmosphere effect.
When you create a new scene, the Atmosphere Editor prompts you to choose one atmosphere among many.
Choose the 'St Petersbourg' atmosphere from the 'Bad weather' collection.
Press the Atmosphere Editor button in the top toolbox and go to the Effects tab.
Select the Rainbow option, press OK and try to render.

Can't see the rainbow?
Then check the position of the sun !
Most people don't know that the sun is always behind you when you see a rainbow. And the arc of the rainbow is always opposite to the sun. The rainbow is diffracted light. This light goes from the sun through the water drops and reflects back. And then we can see the rainbow.

In the World Browser select the 'Sun light'. Drag it behind the camera. In the Front view put the sun close to the horizon line. (See the pictures below)

Now, we can play with the different parameters.
Create another scene and load the Rainy Alaska atmosphere. Press the Atmosphere Editor button, select the 'Effects' tab, and check Realistic colors.
The Intensity controls the overall effect of the rainbow.
It is the main parameter. The 'reality' of a rainbow probably depends on this parameter. Let's see.

Here is a picture with the intensity set at 25%:

Another picture with the intensity set at 60%:

And another one which intensity is set at 90%:

As you can see, the first picture looks rather natural. So, let's set the intensity to 25%.

The next setting you can see is the rainbow size.
This option controls the thickness of a rainbow.

Here are two pictures with different rainbow thickness:

The rainbow size set at 20%:

The rainbow size set at 90%:

The Falloff controls the rainbow length. The smaller value means the longer rainbow in the sky...

Falloff set at 30%:

Falloff set at 70%.

The Secondary bow option creates a second bow. ;) Let's see.
If you want the second bow, go to the'Fog and Haze' tab and set the Fog 'Density' to 145.
This removes the fog near the horizon line.
In the 'Effects'  tab, set the 'Intensity'  to 50% and select the Secondary bow.
Try to render.