Tension Tag
You can use the Tension tag to write information in a Vertex map that defines how much stretching or compression is occurring in each polygon that is being deformed by one or more Deformers.
You can then use this information for a number of purposes. One of the main uses is to create natural-looking folds and stretches as a mesh deforms. This is achieved by loading the Vertex maps generated into vertex map shaders, which are then used as layer masks inside a layer shader. The layer masks are used to blend in the various stretch maps and fold maps in the areas where stretching or compression is occurring.
You can use this layer shader in the displacement channel, for example, to simulate folds on the object. The next picture shows you an example of this effect.
The tag has many other possible uses besides simulating folds. For example, you can use the vertex maps generated to control Cloth parameters, particle emission or foam on the crest of a wave. You can also use the tag to restrict the influence of other Deformers. The possibilities are endless!