The default terrain engine for osgEarth renders an unlimited number of image layers using a tile-level multipass blending technique.

Example usage:

        <terrain driver                   = "mp"
                 skirt_ratio              = "0.05"
                 color                    = "#ffffffff"
                 normalize_edges          = "false"
                 incremental_update       = "false"
                 quick_release_gl_objects = "true"
                 min_tile_range_factor    = "7.0"
                 cluster_culling          = "true" />


skirt_ratio:The “skirt” is a piece of vertical geometry that hides gaps between adjacent tiles with different levels of detail. This property sets the ratio of skirt height to the width of the tile.
color:Color of the underlying terrain (without imagery) in HTML format. Default = “#ffffffff” (opaque white). You can adjust the alpha to get transparency.
 Post-process the normal vectors on tile boundaries to smooth them across tiles, making the tile boundaries less visible when not using imagery.
 When enabled, only visible tiles update when the map model changes (i.e., when layers are added or removed). Non-visible terrain tiles (like those at lower LODs) don’t update until they come into view.
 When true, installs a module that releases GL resources immediately when a tile pages out. This can prevent memory run-up when traversing a paged terrain at high speed. Disabling quick-release may help achieve a more consistent frame rate.

Common Properties:

 The “maximum visible distance” ratio for all tiles. The maximum visible distance is computed as tile radius * this value. (default = 7.0)
 Cluster culling discards back-facing tiles by default. You can disable it be setting this to false, for example if you want to go underground and look up at the surface.