Add InstanceNode test using PBRLighting

jme3-core/src/main/resources/Common/MatDefs/Light/PBRLighting.vert

@@ -76,7 +76,7 @@ void main(){
        texCoord2 = inTexCoord2;
     #endif
 
-    wPosition = (g_WorldMatrix * vec4(inPosition, 1.0)).xyz;
+    wPosition = TransformWorld(modelSpacePos).xyz;
     wNormal  = TransformWorldNormal(modelSpaceNorm);
 
     wTangent = vec4(TransformWorldNormal(modelSpaceTan),inTangent.w);

jme3-examples/src/main/java/jme3test/scene/instancing/TestInstanceNodeWithPbr.java

@@ -0,0 +1,92 @@
+package jme3test.scene.instancing;
+
+import java.util.Locale;
+
+import com.jme3.app.SimpleApplication;
+import com.jme3.font.BitmapText;
+import com.jme3.light.DirectionalLight;
+import com.jme3.material.Material;
+import com.jme3.math.ColorRGBA;
+import com.jme3.math.Vector3f;
+import com.jme3.scene.Geometry;
+import com.jme3.scene.instancing.InstancedNode;
+import com.jme3.scene.shape.Box;
+
+/**
+ * This test specifically validates the corrected PBR rendering when combined
+ * with instancing, as addressed in issue #2435. 
+ * 
+ * It creates an InstancedNode
+ * with a PBR-materialized Box to ensure the fix in PBRLighting.vert correctly
+ * handles world position calculations for instanced geometry.
+ */
+public class TestInstanceNodeWithPbr extends SimpleApplication {
+
+    public static void main(String[] args) {
+        TestInstanceNodeWithPbr app = new TestInstanceNodeWithPbr();
+        app.start();
+    }
+
+    private BitmapText bmp;
+    private Geometry box;
+    private float pos = -5;
+    private float vel = 5;
+
+    @Override
+    public void simpleInitApp() {
+        configureCamera();
+        bmp = createLabelText(10, 20, "<placeholder>");
+
+        InstancedNode instancedNode = new InstancedNode("InstancedNode");
+        rootNode.attachChild(instancedNode);
+
+        Box mesh = new Box(0.5f, 0.5f, 0.5f);
+        box = new Geometry("Box", mesh);
+        Material pbrMaterial = createPbrMaterial(ColorRGBA.Red);
+        box.setMaterial(pbrMaterial);
+
+        instancedNode.attachChild(box);
+        instancedNode.instance();
+
+        DirectionalLight light = new DirectionalLight();
+        light.setDirection(new Vector3f(-1, -2, -3).normalizeLocal());
+        rootNode.addLight(light);
+    }
+
+    private Material createPbrMaterial(ColorRGBA color) {
+        Material mat = new Material(assetManager, "Common/MatDefs/Light/PBRLighting.j3md");
+        mat.setColor("BaseColor", color);
+        mat.setFloat("Roughness", 0.8f);
+        mat.setFloat("Metallic", 0.1f);
+        mat.setBoolean("UseInstancing", true);
+        return mat;
+    }
+
+    private void configureCamera() {
+        flyCam.setMoveSpeed(15f);
+        flyCam.setDragToRotate(true);
+
+        cam.setLocation(Vector3f.UNIT_XYZ.mult(12));
+        cam.lookAt(Vector3f.ZERO, Vector3f.UNIT_Y);
+    }
+
+    private BitmapText createLabelText(int x, int y, String text) {
+        BitmapText bmp = new BitmapText(guiFont);
+        bmp.setText(text);
+        bmp.setLocalTranslation(x, settings.getHeight() - y, 0);
+        bmp.setColor(ColorRGBA.Red);
+        guiNode.attachChild(bmp);
+        return bmp;
+    }
+
+    @Override
+    public void simpleUpdate(float tpf) {
+        pos += tpf * vel;
+        if (pos < -10f || pos > 10f) {
+            vel *= -1;
+        }
+        box.setLocalTranslation(pos, 0f, 0f);
+        bmp.setText(String.format(Locale.ENGLISH, "BoxPosition: (%.2f, %.1f, %.1f)", pos, 0f, 0f));
+    }
+
+}