Make a part of a machine clickable

Goal: let learners press a part of the machine itself, such as a switch, a sensor or a lid, without adding a separate button.

A clickable part is an invisible button that covers one part of an object. The part lights up while a controller or a hand points at it, and learners press it like a button.

Steps

1. Open ALF > Interactivity > Button Injection.

2. Under the list on the left, press + Add a new button.

3. In step 1 Button, set Type to Clickable part. The On an object / In the world choice is replaced by a list of parts.

4. Drag the whole object, for example the machine or board, from the Hierarchy into Object. Its parts are listed below it.

5. Under Parts, click the part learners should press. Each row has a short note:

   Note	Meaning
   box	The part is box-shaped. The clickable area matches it exactly.
   own collider	The part already has a collider. That's the clickable area.
   not a box	The clickable area is a box around each of its pieces, so pointing just beside it can count too.
   already clickable	It has a clickable part already. Edit that one in the list on the left.
   nothing to click (greyed out)	There's nothing visible to click. Pick a part you can see.
   has its own interaction (greyed out)	The part already reacts to the controllers, for example because it can be grabbed. Pick one of its parts instead.

6. Type a Name, for example Power switch. If you leave it empty, it's named Clickable - followed by the part's name.

7. Press Make this part clickable.

8. Optional: in step 1 Button, choose the Highlight colour. The part is tinted with it while it's pointed at. It's amber by default.

9. Go to step 4 Save and press Save the scene.

Result

The clickable part is listed on the left, on its part. It follows the part wherever the part goes.

How learners press it

With	Learners…
A controller	point at the part and press the grip button. The trigger only highlights it.
Their hands	reach for the part and pinch. Poking it with a fingertip doesn't press it.

Good to know

• No position and no label. A clickable part covers its part exactly, so steps 2 Position and 3 Label have nothing to set. To change where it is or how big it is, move, turn or resize the part itself.
• It can't be changed into another type, and other types can't be changed into it. Remove it and place the other type instead.
• The rest of the object still works. If the object can be grabbed, it can still be grabbed anywhere except the clickable part. Pointing at the clickable part presses it and never grabs the object.
• Read the notes under the list. The tool warns you, for example, if another collider covers the part and might catch the click instead.
• Drag from the Hierarchy, not from the Project window. Only objects in your scene have parts that can be made clickable.
• Placing it doesn't make it do anything yet. To make it advance the lesson, see Use a button to advance a lesson step.