public TinBreaklineRendererDefinition( 
   CIMSymbolReference symbolTemplate,
   bool useDefaultSymbol
)

//Must be on the QueuedTask.Run()

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;

//Create the layer to the terrain
var terrainLayer_rd = LayerFactory.Instance.CreateLayer<TerrainLayer>(terrainCP_renderers, map);

var breaklineRendererDef = new TinBreaklineRendererDefinition();
// use default symbol for regular edge but specific symbols for hard,soft,outside
breaklineRendererDef.HardEdgeSymbol = hardEdgeSymbol.MakeSymbolReference();
breaklineRendererDef.SoftEdgeSymbol = softEdgeSymbol.MakeSymbolReference();
breaklineRendererDef.OutsideEdgeSymbol = outsideEdgeSymbol.MakeSymbolReference();

if (surfaceLayer.CanCreateRenderer(breaklineRendererDef))
{
  CIMTinRenderer renderer = surfaceLayer.CreateRenderer(breaklineRendererDef);
  if (surfaceLayer.CanSetRenderer(renderer, SurfaceRendererTarget.Edges))
    surfaceLayer.SetRenderer(renderer, SurfaceRendererTarget.Edges);
}