I have been working with a trial version of Maya over the last few weeks teaching myself basic animation and 3D lighting techniques. In my first week I reconstructed an image from a show I lit several years ago. This past week I tried my hand at animating a little scene. Even simple animation is a wholly new skillset and takes a lot of concentration to make even moderate gains.
This past weekend I shifted to somewhat more familiar terrain, skies and clouds. While the 3D medium is new, I have been lighting sky drops for years. The basic set up included a white translucent rectangle for the sky and some clouds made of nParticles (Maya’s objects that recreate realistic clouds, smoke, and water). Once I got a cloud formation I liked, I stopped the animation at that frame and began lighting. What follows is the same exact cloud formation altered only by changes in the intensity, direction, and color of the light used. The big revelation for me was that because this is a 3D environment I did not need to leave the sky drop as a passive object but rather could have it glow as well as be lit from the front and through from behind. I must admit, I felt a little bit like Neo from The Matrix realizing that the laws of physics are provisional at best.
The above image was lit as close to a true recreation of natural light as possible. The sky had a light blue glow to it and a single light shone and refracted through the clouds to illuminate them. One thing I found particularly interesting was that by simply shifting the colors, angles, and intensity I could invert the image above into the one below. Thus the Cumulus clouds of the above image are transformed into Cirrus clouds below.
Some of my early attempts used a lot of lights since I began from my background in stage lighting. As I worked with the scene I kept taking away more and more lights and found that far from diminishing the image, the quality and dynamism would improve with fewer lights. Some ideas required the use of numerous lights. The image below has a set of lights for the lavender horizon to give it some slight color variation and several lights at the top to light the higher sky in green tones. The clouds too had a variety of lights pointed at them to give a nice range of color and tone.
More directional sunset effects like the one below obviously required multiple lights in order to get the desired effect. But I found multiple lights to be difficult to work with as they quite easily blew out and over exposed the clouds themselves.
The ease of moving and refocusing the lights in a virtual environment makes experimentation fun and easy. In a real world setting it can take a lot of time, effort, and manpower to move and refocus a single light. In virtual environments like this is takes a couple of seconds. Be the interest naturalistic effects like the above or moody more abstract looks like below, lighting in virtual environments gives the designer a wide latitude in terms of what is available to them.
Cloud templates come in several varieties and each have their benefits and drawbacks. Standard steel, like with leaves, provide a cookie cutter cut out of a shape that, with the proper attention to angle and sharpness can be either cartoonish or subtle. Even a template as silly as R78169 can, with the proper focus, turn into a very powerful effect when designing a sky. 
