Linear Forests RFC

Revision History

2/18/12 - Update 4/15/10 - Initial Draft

Status: Implemented in X-Plane 10.0

Normally forests are created in X-Plane by specifying a polygonal boundary (with holes) and then filling it in with trees. Forest polygons provide a high performance, user tunable way to create large areas of vegatation.

This extension provides new DSF syntax to create a forest that only draws trees along the edges or vertices of a forest. This is meant to let authors place trees in smaller, more precisely controlled locations while retaining the performance of the forest system. This extension can provide an alternative to using OBJs for vegetation.

With this extension, the forest polygon parameter now has mode meaning.


 * If it is in the range of 0-255, the parameter is a density for a filled forest (0 = none, 255 = maximum density).
 * If it is in the range of 256-511, the parameter is a density for a forest built along all edges of the polygon except the last of each winding. 256 = no trees, 511 = maximum density.
 * If it is in the range of 512-767, the parameter is ignored, and each forest vertex will receive exactly one tree.

Note: when filling with lines, the last edge of a winding is not filled. This allows forests to be used to make non-closed line sequences, rather than just chains. To use a line-mode polygon to make a closed ring of trees, simply repeat the first vertex of the polygon at the end.