feat: added bindToLookAt3D() which makes a transform look at another transform

Author: AlmasB

fxgl-entity/src/main/kotlin/com/almasb/fxgl/entity/components/TransformComponent.kt

@@ -359,6 +359,22 @@ class TransformComponent(x: Double, y: Double, angle: Double, scaleX: Double, sc
         updateDirection()
     }
 
+    private var boundLookAt: TransformComponent? = null
+
+    fun bindToLookAt3D(other: TransformComponent) {
+        boundLookAt = other
+    }
+
+    fun unbindToLookAt3D() {
+        boundLookAt = null
+    }
+
+    override fun onUpdate(tpf: Double) {
+        boundLookAt?.let {
+            lookAt(it.position3D)
+        }
+    }
+
     /**
      * Move forward on the XZ plane.
      * No Y movement.

fxgl-samples/src/main/java/sandbox/test3d/Collision3DSample.java

@@ -71,7 +71,6 @@ protected void initGame() {
                 .collidable()
                 .buildAndAttach();
 
-        // TODO: camera follow entity, which smoothly continuously calls "look at" entity?
         var camera = getGameScene().getCamera3D();
         camera.getTransform().xProperty().bind(e.xProperty());
         camera.getTransform().yProperty().bind(e.yProperty().subtract(10));

fxgl/src/main/kotlin/com/almasb/fxgl/app/scene/Camera3D.kt

@@ -56,6 +56,8 @@ class Camera3D {
 
     fun update(tpf: Double) {
         tpfMoveSpeed = tpf * moveSpeed
+
+        transform.onUpdate(tpf)
     }
 
     fun moveForward() {