Class CM3LayerTerrain extends CM3Layer
  CM3LayerTerrain Class
 
   Manages a layer that contains an image of the terrain
   This can include:
   - A DEM for elevation values
   - An image to overlay on the DEM
   - A bump map to add surface texture
   - A reflectance map to change how light interacts with the surface
 
  
  Copyright (C) 2020, Humboldt State University, Jim Graham 
  
  This program is free software: you can redistribute it and/or modify it under the terms of the GNU General 
  Public License as published by the Free Software  Foundation, either version 3 of the License, or (at your 
  option) any later  version. 
   
  This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the 
  implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 
  for more details. 
  
  You should have received a copy of the GNU General Public License along with this program. If not, see 
  .
Settings Group: Elevation
Settings Group: TerrainMaterial
| Setting | Name | Type | Options | Default | Comments | 
| Opacity | Opacity | CMTYPE_FLOAT |  | 1 |  | 
| Transparent | Transparent | CMTYPE_BOOLEAN |  | false |  | 
| Color | Color | CMTYPE_COLOR |  | rgb(255,255,255) |  | 
| Side | Side | CMTYPE_ENUMERATED | THREE.DoubleSide, THREE.FrontSide, THREE.BackSide | THREE.DoubleSide |  | 
| map | Overlaid Image (map) | CMTYPE_STRING |  | null |  | 
| bumpMap | Bump Map | CMTYPE_STRING |  | null |  | 
| bumpScale | Bump Scale | CMTYPE_INTEGER |  | 10 |  | 
| specularMap | Reflectance Map | CMTYPE_STRING |  | null |  | 
| specular | Specular Color | CMTYPE_COLOR |  | grey |  | 
Object Functions
Object Functions 
RequestData()
 Called to obtain the data for the layer from a URL.
GetDEMDataset()
 Allows tiles to find the DEM dataset that is associated with this terrain.
SetPyramidURL()
 Function to load data from CanvasMap pryamid files.