Update MatrixJointModelTransform.java

jme3-core/src/main/java/com/jme3/anim/MatrixJointModelTransform.java

@@ -1,3 +1,34 @@
+/*
+ * Copyright (c) 2009-2025 jMonkeyEngine
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
+ *   may be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
 package com.jme3.anim;
 
 import com.jme3.anim.util.JointModelTransform;
@@ -5,21 +36,36 @@ import com.jme3.math.Matrix4f;
 import com.jme3.math.Transform;
 
 /**
- * This JointModelTransform implementation accumulate joints transforms in a Matrix4f to properly
- * support non uniform scaling in an armature hierarchy
+ * An implementation of {@link JointModelTransform} that accumulates joint transformations
+ * into a {@link Matrix4f}. This approach is particularly useful for correctly handling
+ * non-uniform scaling within an armature hierarchy, as {@code Matrix4f} can represent
+ * non-uniform scaling directly, unlike {@link Transform}, which typically handles
+ * uniform scaling.
+ * <p>
+ * This class maintains a single {@link Matrix4f} to represent the accumulated
+ * model-space transform of the joint it's associated with.
  */
 public class MatrixJointModelTransform implements JointModelTransform {
 
-    final private Matrix4f modelTransformMatrix = new Matrix4f();
-    final private Transform modelTransform = new Transform();
+    /**
+     * The model-space transform of the joint represented as a Matrix4f.
+     * This matrix accumulates the local transform of the joint and the model transform
+     * of its parent.
+     */
+    private final Matrix4f modelTransformMatrix = new Matrix4f();
+    /**
+     * A temporary Transform instance used for converting the modelTransformMatrix
+     * to a Transform object when {@link #getModelTransform()} is called.
+     */
+    private final Transform modelTransform = new Transform();
 
     @Override
     public void updateModelTransform(Transform localTransform, Joint parent) {
         localTransform.toTransformMatrix(modelTransformMatrix);
         if (parent != null) {
-            ((MatrixJointModelTransform) parent.getJointModelTransform()).getModelTransformMatrix().mult(modelTransformMatrix, modelTransformMatrix);
+            MatrixJointModelTransform transform = (MatrixJointModelTransform) parent.getJointModelTransform();
+            transform.getModelTransformMatrix().mult(modelTransformMatrix, modelTransformMatrix);
         }
-
     }
 
     @Override
@@ -31,7 +77,8 @@ public class MatrixJointModelTransform implements JointModelTransform {
     public void applyBindPose(Transform localTransform, Matrix4f inverseModelBindMatrix, Joint parent) {
         modelTransformMatrix.set(inverseModelBindMatrix).invertLocal(); // model transform = model bind
         if (parent != null) {
-            ((MatrixJointModelTransform) parent.getJointModelTransform()).getModelTransformMatrix().invert().mult(modelTransformMatrix, modelTransformMatrix);
+            MatrixJointModelTransform transform = (MatrixJointModelTransform) parent.getJointModelTransform();
+            transform.getModelTransformMatrix().invert().mult(modelTransformMatrix, modelTransformMatrix);
         }
         localTransform.fromTransformMatrix(modelTransformMatrix);
     }