Twist and Shear Shader

Node Description & Purpose: Allows to lean the vertical features of a heightfield or procedural terrain into any direction desired. This is very useful for creating overhangs. "Twist and Shear" is good for creating large scale displacements across the entire terrain.

Node Type: Surface Shader

Nodes in Default Scene: n/a

Settings - Main:

• Lean Factor: If a terrain feature was 100% upright, a lean factor of 1 would result in the terrain now leaning at 45 degrees.
• Lean Direction [x,y,z]: The three entry fields stand for the x, y and z direction, in this order. A positive value in the x-field, for example, denotes that the lean direction is along the positive x-axis. A negative value would lean the terrain features along the negative x-axis.
• Base Altitude: The base altitude specifies the height upward from which the Twist and Shear displacement becomes effective.

A heightmap or heightfield is an array of height values, usually in a grid which describe the height at specific points in a defined area. Heightfields are used to represent real-world and virtual terrain in a specific, easily converted format. Most heightfields can be represented as simple image data in grayscale, with black being minimum height and white being maximum height.

In general a “procedure” is a series of steps that should result in a specific and reproducible outcome. In Terragen 2 a “procedural” is a mathematical function describing output which may be visualized and sampled to create anything from terrain to clouds.

Literally, to change the position of something. In graphics terminology to displace a surface is to modify its geometric (3D) structure using reference data of some kind. For example, a grayscale image might be taken as input, with black areas indicating no displacement of the surface, and white indicating maximum displacement. In Terragen 2 displacement is used to create all terrain by taking heightfield or procedural data as input and using it to displace the normally flat sphere of the planet.