Using a Different Skeleton for Models and Animations

User Code & Projects
1

This class that I wrote retargets models and Animations from one Skeleton to another. It’s heavily dependent on both Skeletons using the exact same names for their corresponding bones. It’s worked well for my purposes. Let me know if it works for you.

Here’s the license:

import com.jme3.animation.AnimControl;
import com.jme3.animation.Animation;
import com.jme3.animation.Bone;
import com.jme3.animation.BoneTrack;
import com.jme3.animation.Skeleton;
import com.jme3.animation.SkeletonControl;
import com.jme3.animation.Track;
import com.jme3.material.Material;
import com.jme3.math.Vector3f;
import com.jme3.scene.Geometry;
import com.jme3.scene.Mesh;
import com.jme3.scene.Node;
import com.jme3.scene.Spatial;
import com.jme3.scene.VertexBuffer;
import com.jme3.scene.VertexBuffer.Type;

/**
 * Copyright Alweth on hub.jmonkeyengine.org forums 2016-2017
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software (the "Software"), to 
 * use, and modify the Software subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of 
 * the Software.
 * 
 * The software or any of its derivatives shall not be sold or distributed independently of the expressed intention of 
 * the author.
 * 
 * Any distribution of any of the output of the Software or its derivatives, or any derivative of such output shall 
 * include with it acknowledgement of the contribution of the author of this software, as above, in providing this 
 * software for use, free of charge.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * @author Alweth on hub.jmonkeyengine.org forums
 *
 */
public final class AnimationRetargeter {
	private AnimationRetargeter() {}
	
	//TODO: If a mesh has already been cloned and retargeted to the newSkeleton, then just pass that back instead of deepCloning it again and 
	//everything.
	
	public static Spatial retarget (Spatial spatial, Skeleton newSkeleton) {
		retarget(spatial, null, newSkeleton);
		//spatial.updateGeometricState();
		return spatial;
	}
	
	public static void retarget (Spatial spatial, Skeleton oldSkeleton, Skeleton newSkeleton) {
		Skeleton use = oldSkeleton;
		SkeletonControl sc = spatial.getControl(SkeletonControl.class);
		if (sc != null) {
			use = sc.getSkeleton();
			spatial.removeControl(SkeletonControl.class);
			//sc = new SkeletonControl(newSkeleton);
			//spatial.addControl(sc);
		}
		spatial.removeControl(AnimControl.class);
		
		if (use != null && spatial instanceof Geometry) {
			Mesh mesh = ((Geometry)spatial).getMesh();
			if (mesh != null) {
				mesh = mesh.deepClone();
				retarget(mesh, use, newSkeleton);
				((Geometry)spatial).setMesh(mesh);
				//((Geometry)spatial).getMaterial().clearParam("BoneMatrices");
				Material m = ((Geometry)spatial).getMaterial();
				if (m != null) {
					m.clearParam("BoneMatrices");
				}
			}
		} else if (spatial instanceof Node) {
			for (Spatial child : ((Node)spatial).getChildren()) {
				retarget(child, use, newSkeleton);
			}
		}
	}
	
	public static void retarget (Mesh mesh, Skeleton oldSkeleton, Skeleton newSkeleton) {
		byte[] map = generateMap(oldSkeleton, newSkeleton);
		int count = map.length;
		retargetBuffer(mesh, map, mesh.getBuffer(Type.BoneIndex), count);
		retargetBuffer(mesh, map, mesh.getBuffer(Type.HWBoneIndex), count);		
	}
	
	private static void retargetBuffer (Mesh mesh, byte[] map, VertexBuffer buff, int count) {
		if (buff != null) {
			int components = buff.getNumComponents();
			int elements = buff.getNumElements();
			
			for (int i = 0; i < elements; i++) {
				for (int j = 0; j < components; j++) {
					byte o = (byte)buff.getElementComponent(i, j);
					
					if (o >= 0 && o < count) {
						byte n = map[o];
						if (n != -1) {
							buff.setElementComponent(i, j, n);
						}
					}
				}
			}
			
			mesh.prepareForAnim(true); //TODO: Check if this is actually needed.
		}
	}
	
	public static void retarget (Animation a, Skeleton oldSkeleton, Skeleton newSkeleton) {
		byte[] map = generateMap(oldSkeleton, newSkeleton);
		
		Track[] tracks = a.getTracks();
		Track[] to = new Track[tracks.length];
		
		int toI = 0;
		for (int i = 0; i < tracks.length; i++) {
			if (tracks[i] instanceof BoneTrack) {
				BoneTrack t = (BoneTrack)tracks[i];
				int index = map[t.getTargetBoneIndex()];
				if (index != -1) {
					Vector3f[] scales = t.getScales();
					if (scales != null) {
						to[toI] = new BoneTrack(index, t.getTimes(), t.getTranslations(), t.getRotations(), scales);
					} else {
						to[toI] = new BoneTrack(index, t.getTimes(), t.getTranslations(), t.getRotations());
					}
					a.removeTrack(t);
					toI++;
				}
			}
		}
		Track[] out = new Track[toI];
		System.arraycopy(to, 0, out, 0, toI);
		a.setTracks(out);
	}

	private static byte[] generateMap (Skeleton from, Skeleton to) {
		int count = from.getBoneCount();
		byte[] map = new byte[count];
		
		for (int i = 0; i < count; i++) {
			Bone bone = from.getBone(i);
			int index = to.getBoneIndex(bone.getName());
			while (index == -1) {
				bone = bone.getParent();
				if (bone == null) {
					break;
				}
				index = to.getBoneIndex(bone.getName());
			}
			map[i] = (byte)index;
		}
		
		return map;
	}
}
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