add note about collisions

Author: borbware

unity-cookbook/collision-slides.html

@@ -31,7 +31,7 @@ <h2 id="colliders">Colliders</h2>
 </li>
 </ul>
 </section>
-</foreignObject></svg><svg data-marpit-svg="" viewBox="0 0 1280 720"><foreignObject width="1280" height="720"><section id="3" data-marpit-fragments="7" data-paginate="true" data-class="invert" data-footer="For more event methods, see [Script Reference: Monobehaviour Messages](https://docs.unity3d.com/ScriptReference/MonoBehaviour.html#Messages)" data-heading-divider="3" lang="en-US" class="invert" data-marpit-pagination="3" style="--paginate:true;--class:invert;--footer:For more event methods, see [Script Reference: Monobehaviour Messages](https://docs.unity3d.com/ScriptReference/MonoBehaviour.html#Messages);--heading-divider:3;" data-marpit-pagination-total="8">
+</foreignObject></svg><svg data-marpit-svg="" viewBox="0 0 1280 720"><foreignObject width="1280" height="720"><section id="3" data-marpit-fragments="8" data-paginate="true" data-class="invert" data-footer="For more event methods, see [Script Reference: Monobehaviour Messages](https://docs.unity3d.com/ScriptReference/MonoBehaviour.html#Messages)" data-heading-divider="3" lang="en-US" class="invert" data-marpit-pagination="3" style="--paginate:true;--class:invert;--footer:For more event methods, see [Script Reference: Monobehaviour Messages](https://docs.unity3d.com/ScriptReference/MonoBehaviour.html#Messages);--heading-divider:3;" data-marpit-pagination-total="8">
 <h2 id="collision-events">Collision events</h2>
 <ul>
 <li data-marpit-fragment="1">
@@ -55,6 +55,9 @@ <h2 id="collision-events">Collision events</h2>
 <li data-marpit-fragment="7">
 <p>See the links for code examples!</p>
 </li>
+<li data-marpit-fragment="8">
+<p><em><strong>Note:</strong></em> To make the collision happen, at least one of the colliding GameObjects has to have a RigidBody component attached to it!</p>
+</li>
 </ul>
 <footer>For more event methods, see <a href="https://docs.unity3d.com/ScriptReference/MonoBehaviour.html#Messages">Script Reference: Monobehaviour Messages</a></footer>
 </section>

unity-cookbook/collision.md

@@ -30,6 +30,7 @@ math: mathjax
 * [`OnCollisionExit`](https://docs.unity3d.com/ScriptReference/Collider.OnCollisionExit.html) / [`OnCollisionExit2D`](https://docs.unity3d.com/ScriptReference/Collider2D.OnCollisionExit2D.html)
   * when collision with another collider ends
 * See the links for code examples!
+* ***Note:*** To make the collision happen, at least one of the colliding GameObjects has to have a RigidBody component attached to it!
 
 <!-- _footer: "For more event methods, see [Script Reference: Monobehaviour Messages](https://docs.unity3d.com/ScriptReference/MonoBehaviour.html#Messages)" -->