Creating skylines using procedural textures
In this tutorial I will show you how to make some simple skies using procedural textures. What does procedural mean? Procedural textures are mathematical, which means there is not a single photo or drawing used to create these clouds. They are made using 3ds max's built-in textures, such as noise and smoke.
But why? Isn't it easier to just use photos?
Yes, photos are a lot easier and faster to set up, but they are not as flexible as procedural textures. By changing some of the math values, you can quickly change the look of the sky, even animating the clouds! And since no textures are used, resolution is not an issue. You can zoom into these clouds and never ever see a pixel. Neat!
Obviously, they're not photoreal, but they still look very nice. I think they look great in more stylized productions. Of course, these skies can be improved even further, your creativity is the only limit.
Although some terms and stills are taken from 3ds Max software, the principles and techniques presented in this tutorial should be applicable to most 3D software packages.
The tutorial assumes basic knowledge of 3ds Max. Use the 3ds Max online help file if you are unsure about the more detailed aspects of the tuturial.
The method is very simple, and can be expanded on as much as you want. We will create hemispheres that represent the sky and the different layers of clouds. Using a combination of gradients and noise textures, we will then create transparency-mapped clouds. And using some material and texture instancing, we will create a sky that's very easy to change.
Building the geometry
Start by making a single sphere. Make it rather large, after all this is the sky we're making! Now cut it in half to make a hemisphere. We will be inside this object, so make sure to invert the normals. Now put two UVW mapping sets on this hemisphere. Make the first a planar mapping from the top, set it to Map Channel 1. Make the second a planar mapping from the side, and set it to Map Channel 2. Make sure both UVW sets fit the hemisphere tightly.
Duplicate this sphere to get two additional spheres, scale the copies down in height so that they are 25% as tall as the original. Make one of the copies slightly lower than the other. These two flattened hemispheres will be our cloud layers. Name the original hemisphere 'hemiSky'. Name the tallest of the copies 'hemiBrightClouds', and the lowest 'hemiShadowClouds'.
Now create a camera, place it on the ground in the center of the hemispheres. The skies will look the best if the camera is perfectly in the center. Make sure that the camera is pointing out toward the hemispheres. Put a rather wide lens on the camera, so that we can see a large portion of the sky. I set my camera to a 20mm lens. Make a test render to make sure that the camera see the hemispheres and that their normals are pointing inwards.
Let's continue to part two, where we will set up the procedural textures.