public void SetPoint( 
   int patchIndex,
   int pointIndex,
   MapPoint point
)

{
  TextureResource brickTextureResource = null;
  BasicMaterial brickMaterialTexture = new BasicMaterial();
  var coords = new List<Coordinate3D>();

  // create the multipatchBuilderEx object
  var builder = new ArcGIS.Core.Geometry.MultipatchBuilderEx(multipatch);

  // check some properties
  bool hasM = builder.HasM;
  bool hasZ = builder.HasZ;
  bool hasID = builder.HasID;
  bool isEmpty = builder.IsEmpty;
  bool hasNormals = builder.HasNormals;

  var patches = builder.Patches;
  int patchCount = patches.Count;

  // if there's some patches
  if (patchCount > 0)
  {
    int pointCount = builder.GetPatchPointCount(0);

    // replace the first point in the first patch
    if (pointCount > 0)
    {
      // get the first point
      var pt = builder.GetPoint(0, 0);
      builder.SetPoint(0, 0, mapPoint);
    }

    // check which patches currently contain the texture
    var texture = builder.QueryPatchIndicesWithTexture(brickTextureResource);

    // assign a texture material
    patches[0].Material = brickMaterialTexture;
  }

  // update the builder for M awareness
  builder.HasM = true;
  // synchronize the patch attributes to match the builder attributes
  //   in this instance because we just set HasM to true on the builder, each patch will now get a default M value for it's set of coordinates
  builder.SynchronizeAttributeAwareness();

  // call ToGeometry to get the multipatch
  multipatch = builder.ToGeometry() as Multipatch;

  // multipatch.HasM will be true
}