/// <summary>
        /// Recursive function that processes the entire scene graph, collecting up
        /// all of the animation data.
        /// </summary>
        private void ProcessAnimationsRecursive(NodeContent input)
        {
            // Look up the bone for this input channel
            int inputBoneIndex;
            if (bones.TryGetValue(input.Name, out inputBoneIndex))
            {
                // Save the transform
                boneTransforms[inputBoneIndex] = input.Transform;
            }


            foreach (KeyValuePair<string, AnimationContent> animation in input.Animations)
            {
                // Do we have this animation before?
                AnimationClip clip;
                string clipName = animation.Key;

                if (!clips.TryGetValue(clipName, out clip))
                {
                    // Never seen before clip
                    clip = new AnimationClip();
                    modelExtra.Clips.Add(clip);

                    // Retain by name
                    clips[clipName] = clip;

                    clip.Name = clipName;
                    foreach (ModelBoneContent bone in model.Bones)
                    {
                        AnimationClip.Bone clipBone = new AnimationClip.Bone();
                        clipBone.Name = bone.Name;

                        clip.Bones.Add(clipBone);
                    }
                }

                // Ensure the duration is always set
                if (animation.Value.Duration.TotalSeconds > clip.Duration)
                    clip.Duration = (float)animation.Value.Duration.TotalSeconds;

                //
                // For each channel, determine the bone and then process all of the 
                // keyframes for that bone.
                //

                foreach (KeyValuePair<string, AnimationChannel> channel in animation.Value.Channels)
                {
                    // What is the bone index?
                    int boneIndex;
                    if (!bones.TryGetValue(channel.Key, out boneIndex))
                        continue;       // Ignore if not a named bone

                    if (UselessAnimationTest(boneIndex))
                        continue;

                    // I'm collecting up in a linked list so we can process the data
                    // and remove redundant keyframes
                    LinkedList<AnimationClip.Keyframe> keyframes = new LinkedList<AnimationClip.Keyframe>();
                    foreach (AnimationKeyframe keyframe in channel.Value)
                    {
                        Matrix transform = keyframe.Transform;      // Keyframe transformation

                        AnimationClip.Keyframe newKeyframe = new AnimationClip.Keyframe();
                        newKeyframe.Time = (float)keyframe.Time.TotalSeconds;
                        newKeyframe.SetTransform(transform);

                        keyframes.AddLast(newKeyframe);
                    }

                    LinearKeyframeReduction(keyframes);

                    foreach (AnimationClip.Keyframe keyframe in keyframes)
                    {
                        clip.Bones[boneIndex].Keyframes.Add(keyframe);
                    }

                }


            }

            foreach (NodeContent child in input.Children)
            {
                ProcessAnimationsRecursive(child);
            }
        }
        /// <summary>
        /// Entry point for animation processing. 
        /// </summary>
        /// <param name="model"></param>
        /// <param name="input"></param>
        /// <param name="context"></param>
        private void ProcessAnimations(ModelContent model, NodeContent input, ContentProcessorContext context)
        {
            // First build a lookup table so we can determine the 
            // index into the list of bones from a bone name.
            for (int i = 0; i < model.Bones.Count; i++)
            {
                bones[model.Bones[i].Name] = i;
            }

            // For saving the bone transforms
            boneTransforms = new Matrix[model.Bones.Count];

            //
            // Collect up all of the animation data
            //

            ProcessAnimationsRecursive(input);

            // Ensure there is always a clip, even if none is included in the FBX
            // That way we can create poses using FBX files as one-frame 
            // animation clips
            if (modelExtra.Clips.Count == 0)
            {
                AnimationClip clip = new AnimationClip();
                modelExtra.Clips.Add(clip);

                string clipName = "Take 001";

                // Retain by name
                clips[clipName] = clip;

                clip.Name = clipName;
                foreach (ModelBoneContent bone in model.Bones)
                {
                    AnimationClip.Bone clipBone = new AnimationClip.Bone();
                    clipBone.Name = bone.Name;

                    clip.Bones.Add(clipBone);
                }
            }

            // Ensure all animations have a first key frame for every bone
            foreach (AnimationClip clip in modelExtra.Clips)
            {
               
                foreach (int b in bones.Values)
                {
                    List<AnimationClip.Keyframe> keyframes = clip.Bones[b].Keyframes;
                    if (keyframes.Count == 0 || keyframes[0].Time > 0)
                    {
                        AnimationClip.Keyframe keyframe = new AnimationClip.Keyframe();
                        keyframe.Time = 0;
                        keyframe.SetTransform(boneTransforms[b]);
                        keyframes.Insert(0, keyframe);
                    }
                }
            }
        }