// applies to Terrain layers only
var dirtyAreaRendererDef = new TerrainDirtyAreaRendererDefinition();
// accept default labels, symbolTemplate
var terrainLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<TerrainLayer>().FirstOrDefault();
if (terrainLayer == null)
return;
if (terrainLayer.CanCreateRenderer(dirtyAreaRendererDef))
{
CIMTinRenderer renderer = terrainLayer.CreateRenderer(dirtyAreaRendererDef);
if (terrainLayer.CanSetRenderer(renderer, SurfaceRendererTarget.DirtyArea))
terrainLayer.SetRenderer(renderer, SurfaceRendererTarget.DirtyArea);
}