public double MinValue {get; set;}

{
  // Note: call within QueuedTask.Run()
  {
    var fields = pointCloudSceneLayer.GetAvailablePointCloudRendererFields(
                            PointCloudRendererType.StretchRenderer);
    var stretchDef = new PointCloudRendererDefinition(
                              PointCloudRendererType.StretchRenderer)
    {
      //Will be either ELEVATION or INTENSITY
      Field = fields[0]
    };
    //Create the CIM Renderer
    var stretchRenderer = pointCloudSceneLayer.CreateRenderer(stretchDef)
                                        as CIMPointCloudStretchRenderer;
    //Apply a color ramp
    var style = Project.Current.GetItems<StyleProjectItem>()
                                    .First(s => s.Name == "ArcGIS Colors");
    var colorRamp = style.SearchColorRamps("").First();
    stretchRenderer.ColorRamp = colorRamp.ColorRamp;
    //Apply modulation
    stretchRenderer.ColorModulation = new CIMColorModulationInfo()
    {
      MinValue = 0,
      MaxValue = 100
    };
    //apply the renderer
    pointCloudSceneLayer.SetRenderer(stretchRenderer);
  }
}

{
  // Note: call within QueuedTask.Run()
  {
    var def = pointCloudSceneLayer.GetDefinition() as CIMPointCloudLayer;
    //Get the ColorModulation off the renderer
    var modulation = def.Renderer.ColorModulation;
    if (modulation == null)
      modulation = new CIMColorModulationInfo();
    //Set the minimum and maximum intensity as needed
    modulation.MinValue = 0;
    modulation.MaxValue = 100.0;
    //apply back
    def.Renderer.ColorModulation = modulation;
    //Commit changes back to the CIM
    pointCloudSceneLayer.SetDefinition(def);
  }
}