public class TerrainDirtyAreaRendererDefinition : TinSimpleRendererDefinition 

{
  var terrainCP_renderers = new TerrainLayerCreationParams(terrain);
  terrainCP_renderers.Name = "My LAS Layer";
  terrainCP_renderers.IsVisible = true;

  // define the edge type renderer - use defaults
  var edgeRD = new TinBreaklineRendererDefinition();

  // define the face/surface renderer
  var faceRD = new TinFaceClassBreaksRendererDefinition();
  faceRD.ClassificationMethod = ClassificationMethod.NaturalBreaks;
  // accept default color ramp, breakCount

  // define the dirty area renderer - use defaults
  var dirtyAreaRD = new TerrainDirtyAreaRendererDefinition();

  // add renderers to dictionary
  var t_dict = new Dictionary<SurfaceRendererTarget, TinRendererDefinition>();
  t_dict.Add(SurfaceRendererTarget.Edges, edgeRD);
  t_dict.Add(SurfaceRendererTarget.Surface, faceRD);
  t_dict.Add(SurfaceRendererTarget.DirtyArea, dirtyAreaRD);

  // assign dictionary to creation params
  terrainCP_renderers.RendererDefinitions = t_dict;
  // Note: Needs QueuedTask to run
  {
    //Create the layer to the terrain
    var terrainLayer_rd = LayerFactory.Instance.CreateLayer<TerrainLayer>(terrainCP_renderers, map);
  }
}

{
  var dirtyAreaRendererDef = new TerrainDirtyAreaRendererDefinition();
  // accept default labels, symbolTemplate

  if (terrainLayer == null)
    return;
  // Note: Needs QueuedTask to run
  {
    if (terrainLayer.CanCreateRenderer(dirtyAreaRendererDef))
    {
      CIMTinRenderer renderer = terrainLayer.CreateRenderer(dirtyAreaRendererDef);
      if (terrainLayer.CanSetRenderer(renderer, SurfaceRendererTarget.DirtyArea))
        terrainLayer.SetRenderer(renderer, SurfaceRendererTarget.DirtyArea);
    }
  }
}