Contains information for a skin transform.
            // "This template is instantiated on a per-mesh basis. Within a mesh, a sequence of n
            // instances of this template will appear, where n is the number of bones (X file frames)
            // that influence the vertices in the mesh. Each instance of the template basically defines
            // the influence of a particular bone on the mesh. There is a list of vertex indices, and a
            // corresponding list of weights.
            // template SkinWeights
            // {
            //     STRING transformNodeName;
            //     DWORD nWeights;
            //     array DWORD vertexIndices[nWeights];
            //     array float weights[nWeights];
            //     Matrix4x4 matrixOffset;
            // }
            // - The name of the bone whose influence is being defined is transformNodeName,
            // and nWeights is the number of vertices affected by this bone.
            // - The vertices influenced by this bone are contained in vertexIndices, and the weights for
            // each of the vertices influenced by this bone are contained in weights.
            // - The matrix matrixOffset transforms the mesh vertices to the space of the bone. When concatenated
            // to the bone's transform, this provides the world space coordinates of the mesh as affected by the bone."
            // (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/
            //  directx9_c/dx9_graphics_reference_x_file_format_templates.asp)
            //


            // Reads in a bone that contains skin weights.  It then adds one bone weight
            //  to every vertex that is influenced by ths bone, which contains the name of the bone and the
            //  weight.
            public void ImportSkinWeights()
            {
                isSkinned = true;
                string boneName = tokens.SkipName().NextString();
                // an influence is an index to a vertex that is affected by the current bone
                int          numInfluences = tokens.NextInt();
                List <int>   influences    = new List <int>();
                List <float> weights       = new List <float>();

                for (int i = 0; i < numInfluences; i++)
                {
                    influences.Add(tokens.NextInt());
                }
                for (int i = 0; i < numInfluences; i++)
                {
                    weights.Add(tokens.NextFloat());
                    if (weights[i] == 0)
                    {
                        influences[i] = -1;
                    }
                }
                influences.RemoveAll(delegate(int i) { return(i == -1); });
                weights.RemoveAll(delegate(float f) { return(f == 0); });

                while (tokens.Peek == ";")
                {
                    tokens.NextToken();
                }

                // Add the matrix that transforms the vertices to the space of the bone.
                // we will need this for skinned animation.
                Matrix blendOffset = tokens.NextMatrix();

                ContentUtil.ReflectMatrix(ref blendOffset);
                skinTransformDictionary.Add(boneName, blendOffset);
                SkinTransformContent trans = new SkinTransformContent();

                trans.BoneName  = boneName;
                trans.Transform = blendOffset;
                skinTransforms.Add(trans);
                // end of skin weights
                tokens.SkipToken();

                // add a new name/weight pair to every vertex influenced by the bone
                for (int i = 0; i < influences.Count; i++)
                {
                    skinInfo[influences[i]].Add(new BoneWeight(boneName,
                                                               weights[i]));
                }
            }
            /// <summary>
            /// Converts the bone weight collections into working vertex channels by using the
            /// provided bone index dictionary.  Converts bone names into indices.
            /// </summary>
            /// <param name="boneIndices">A dictionary that maps bone names to their indices</param>
            public void AddWeights(Dictionary <string, int> boneIndices)
            {
                if (!isSkinned)
                {
                    return;
                }

                Dictionary <string, int> meshBoneIndices = new Dictionary <string, int>();
                int currentIndex = 0;

                // The bone indices are already sorted by index
                foreach (KeyValuePair <string, int> k in boneIndices)
                {
                    if (skinTransformDictionary.ContainsKey(k.Key))
                    {
                        meshBoneIndices.Add(k.Key, currentIndex++);
                        SkinTransformContent transform = new SkinTransformContent();
                        transform.BoneName  = k.Key;
                        transform.Transform = skinTransformDictionary[k.Key];
                        skinTransforms.Add(transform);
                    }
                }
            }