From 76146ddeb06ea5300df9370df112826c5698b8d6 Mon Sep 17 00:00:00 2001
From: Almas Baimagambetov <almaslvl@gmail.com>
Date: Mon, 19 Sep 2022 13:56:29 +0100
Subject: [PATCH] feat: added bindToLookAt3D() which makes a transform look at
 another transform

---
 .../fxgl/entity/components/TransformComponent.kt | 16 ++++++++++++++++
 .../java/sandbox/test3d/Collision3DSample.java   |  1 -
 .../kotlin/com/almasb/fxgl/app/scene/Camera3D.kt |  2 ++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/fxgl-entity/src/main/kotlin/com/almasb/fxgl/entity/components/TransformComponent.kt b/fxgl-entity/src/main/kotlin/com/almasb/fxgl/entity/components/TransformComponent.kt
index f2d58d8e6..3800a06f6 100644
--- a/fxgl-entity/src/main/kotlin/com/almasb/fxgl/entity/components/TransformComponent.kt
+++ b/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.
diff --git a/fxgl-samples/src/main/java/sandbox/test3d/Collision3DSample.java b/fxgl-samples/src/main/java/sandbox/test3d/Collision3DSample.java
index b5766e38f..820fa4054 100644
--- a/fxgl-samples/src/main/java/sandbox/test3d/Collision3DSample.java
+++ b/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));
diff --git a/fxgl/src/main/kotlin/com/almasb/fxgl/app/scene/Camera3D.kt b/fxgl/src/main/kotlin/com/almasb/fxgl/app/scene/Camera3D.kt
index ee8436436..ae31ba8dd 100644
--- a/fxgl/src/main/kotlin/com/almasb/fxgl/app/scene/Camera3D.kt
+++ b/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() {