09: A Mazing Puzzle (Part 3)

Learning Target

• Add collision triggers
• Use scripts to react to collision triggers

Resources

Door Models:

• • Door.blend
  • Cage Door.blend

Starter Scripts:

• • DoorMechanism.cs
  • ActivateDoor.cs

Optional Resources:

• • Toggle Switch.blend
  • ToggleSwitch.cs

Instructions

Step 1: 

Two door models have been provided. You will need to:

• • Import the models into your Models folder
  • Create original prefabs of the doors
  • Assign materials to the doors
  • Add a collision box to prevent passage by the player

Then, find 2 or 3 spots to locate doors in your maze and add them to your scene. 

Step 2:

It will look a lot better if our doors open, rather than just disappear. To do this, we'll create a small C# script (or use the template above). 

Note: class-level variables are called several different things in different contexts. Here are some commonly used terms:

• • class attributes
  • member variables
  • fields

Your script will need these public member variables so you can make adjustments:

• • IsOpen (boolean)
  • Speed (floating point)
  • OpenHeight (floating point)

You'll also need these two private fields to keep track of positions: 

• • upPosition
  • downPosition

Step 3:

When the game first starts, we need to store both the up and down positions for that specific door. To store the "up" position, we just need to move the starting position along the y-axis. For example,

    upPosition = this.transform.position + new Vector3(0, OpenHeight, 0);

We can slowly move from our current location to a destination position using the MoveTowards() method. This is not complete code, but shows what we are trying to do:

this.transform.position = Vector3.MoveTowards( current position of door , target position of door , distance to move this frame);

distance to move per frame = Speed * Time.DeltaTime;

We also need to use a conditional (if statement) for this to work properly in both directions. 

if(IsOpen) {
  // move to the up position
} else {
  // move to the down position
}

Step 4:

We need a way to tell the doors to open.

Create a Prefab Variant for one or more of your maze blocks. Add a new collision box in the player's pathway.

Change this collision box to be a trigger, but be sure to keep the others as regular colliders.

Step 5:

When the player hits a door trigger, we need to actually control one of the doors. Create a new C# script (or use the template above). The script will need at least two public variables:

• • Door (DoorMechanism)
  • IsOpener (boolean)
  • Optional: IsReversible (boolean)

You'll need to add a new function:

void OnTriggerEnter(Collider other) {

}

This function will execute whenever the player moves into the trigger collider. You will be able to tell the door to open by doing something like this:

Door.IsOpen = true;

However, you should only open the door if that is the script's current purpose. Otherwise, you should close the door.

IsReversible?

To make the door's operation reversible, we can use a "flip-flop" code structure in ActivateDoor.cs. It would look something like this:

if(IsReversible) {
     if(IsOpener) {
          // make this activator a closer
     } else {
          // make this activator an opener
     }
}

Don't forget to add an else statement for when the activator is NOT reversible.

Grading

For grades A to D, all requirements need to be met for that grade band.