Animated Easy Clouds
I read somewhere online that “...clouds are formed when warm, moist air rises and cools..." Just that description alone implies movement, and while we don’t always get to see this kinetic activity in a still image, the ability to simulate this phenomenon in an image sequence is a wonderful component of Terragen clouds.
Let’s explore this feature using an Easy Cloud and see what Terragen can do. Add an "Easy Cloud Mid Level: Altocumulus Castellanus small" to the default Terragen project.
Reduce the Easy Cloud’s "Radius" to 10,000 meters and temporarily increase the "Cloud density" so we can see it better. Just for good measure, make a note of the Easy Cloud’s Y axis value in the "Centre" parameter, as it’s about to change.
In the 3D Preview, hover your mouse over the location you want to place your cloud, right-click and select “Copy Coordinates”. Click the “Copy/paste coordinates” button to the right of the Easy Cloud’s "Centre" parameter and paste the values. You may need to adjust the Y axis value of the Easy Cloud’s "Centre" parameter because the sampled coordinates included the height of the terrain, and the clouds may have disappeared under the ground.
To raise the Easy Cloud back up to its previous position, you can type the value back into the Easy Cloud’s "Centre" Y axis field, or right-click in the 3D Preview and choose “Select Object or Shader” and the name of the cloud from the Object List.
With the cloud selected, hover the mouse over any of its axis handles until they become highlighted then drag the cloud around in the scene.
Two parameters located on the Easy Cloud’s “Anim” tab, help us put some life into the cloud, the “Enable drift” parameter and the “Enable evolution” parameter.
We can set how fast the cloud moves across the landscape with the "Drift speed (m/s)", which is measured in meters per second. The larger the value the greater the distance of travel per frame. The Drift Heading sets the direction the clouds will move in, from 0 to 360 degrees.
The "Evolution speed (m/s)" sets how rapidly the cloud shape changes over time, by moving its internal textures up or down on the Y axis. The larger the value the greater the shape changes each frame.
This video shows both the Drift and Evolution parameters enabled.
Both these motion parameters create a constant speed, but the "Time warp" parameter allows you to modify this by setting control frames on the animation timeline.
Now it’s just a process of fine tuning the other cloud parameters to get the look you want. This entails adjusting the cloud type, depth, and coverage. For Altocumulus type clouds, "Model 3.9.04" tends to produce rougher and more billowy clouds than "Model 3.9.07". When you’re happy with the shape and size of the cloud, then return the Easy Cloud’s "Density" to a much smaller value.
You can download a Terragen Project file for this tutorial to further explore animating an Easy Cloud. File:Tutorial AnimatedEasyClouds.tgd
A parameter is an individual setting in a node parameter view which controls some aspect of the node.