Creating a Transforming Adventure Boss
For a beginner boss tutorial, see this tutorial: Creating a Simple Adventure Boss
In this tutorial you will see some examples on how to create a transforming adventure boss! Since this is a tutorial for more advanced users we'll mostly just go through what objects can be used and assume you already know some of the basics of Principia, e.g how to connect and build simple things. If you're very new to Principia, you should check out some of the beginner tutorials first.
You will find a finished example level at the bottom of this page.
Phase 1: Destructible Parts (Legs)
The legs used in this example are the same as in the Simple Walker tutorial but duplicated to make it a four legged boss.
To make the player able to shoot off the legs we can use a FX emitter to destroy the connections after x amount of damage and make the legs fall off.
Basic objects used for destructible legs:
- Impact sensor - To sense when the leg has been hit
- Condenser - To calculate the damage done to the leg
- FX Emitter - To destroy connections and make explosions
- Auto Absorber - Use with timer to remove the legs some time after being destroyed
Use "Connection Edit" and click a connection you want to make destructible and decrease the strength slider just a bit (0.95). Add an FX emitter somewhere near it and set its config to "Destroy Connections", and "Explosion" if you want explosions when its being destroyed.
To activate the FX emitter after a certain amount of damage we can calculate the health of the legs by using an Impact sensor connected to a Condenser. See Boss HP below for a more detailed example. Make sure to have a separate HP calculation for the legs.
To delete the legs after they fall off you can connect a Timer to an Auto Absorber. Set the timer to e.g 2 seconds and connect it to the FX emitter output socket.
Phase 2: Activate Hovering
To make the boss start hovering over the player after the legs have been destroyed you can use these objects:
- Toggler - To activate the rockets and used objects after the legs have been destroyed
- Rocket
- Proximity sensor
- Tiltmeter
- Gyroscope
- Servo Motor - To change angle of some rockets when the boss is tilting
- Object finder - To find the player's angle and hover towards it
- Stabilizer
For a more detailed tutorial for basic hovering, see this hovercraft tutorial.
The amount of Rockets that you should use depends on the size and weight of the boss.
Here's an example of a setup that will make the boss hover:
- Four pointed down rockets (two at each side) that are connected to a Proximity sensor at the bottom. The proximity sensor senses how far the boss is from the ground and powers the rockets according to that.
- Two rockets that are activated by the tiltmeter and attached to Servo Motors that are connected to a gyroscope.
- Four rockets that point to left/right and are connected to proximity sensors at the sides and/or an Object Finder to find the angle of the player. Use together with a sincos to convert an angle to positive x/y and negative x/y.
- Some extra thrusters if needed to fine tune the stability
Add a stabilizer if needed.
Phase 2: Activate Body Parts (Shooting Arms & Head)
To activate new body parts after the legs have been destroyed you can simply hide them behind a body made of e.g plastic boxes or breadboards, then use Linear Servos or Linear Motors uncover them when activated.
If you have separated body parts like the head in this tutorial example, you can use rubber beams attached to Linear Servos to lock them in place.
To make the Arms or other body parts destructible, see the steps for destructible parts.
Phase 3: Moving Head
In this example: After the body is destroyed the head with two eyes will be dropped on the ground and balance itself on a wheel. For a transformation like this, hide the head or separated body part behind the main body, then when the body is damaged enough, use Auto Absorber to remove it and only the separated body part will remain. Use a Toggler to activate the objects needed so it doesn't move around inside the boss.
Boss HP & visible HP bar
Objects needed:
The condenser can be used as HP for the boss. A condenser has two inputs, IN0 and IN1. IN0 will "fill" the condenser. Send 0.1 to it and it increments its internal value by 0.1, for example. IN1 decrements the condenser. The output, OUT0, is the percentage of how filled the condenser is. If you read 1.0 from OUT0, it means it is full, and 0.0 means it is empty.
You can set the condenser's Initial Fraction to 1 and Max Value to 1. Attach Impact Sensors where the boss will take damage. Connect the Impact Sensors to a sub, set the sub to 0.9 for example. Connect the Sub to the condenser. Now when the Impact sensors have been hit a value of 0.10 will be decremented from the condenser. Add a ceil and inverter to only output 1 when the condenser (HP) is empty. Then you can connect it to a Game Manager to complete the game or a toggler to activate some other features on the boss. So when the boss has been hit about 10 times (this might vary a bit depending on the sensitivity used on the impact sensors). If you want it to have more HP, adjust the values used for the condenser and/or sub.
If you want the boss HP to be visible to the player, there are different ways you can do that:
Using a Grapher
The simplest way is to connect the condenser used for the HP to a Grapher and attach it somewhere on the boss.
Using Active Displays
The HP bar we're using for the example level on this page is this one, it uses Active Displays lined up together to display the current boss health.
Credits to that guy for this method https://principia-web.se/archive/level/4471 You can click edit to see how it's made or copy it with multi-select.
Using a Linear Servo
This method uses a Linear Servo and colored plastic beams on different layers to create a mechanical HP bar.
You can place it somewhere on the side or on the boss if there is space.
Other useful tips
- You can use a Time Ctrl with a Timer for a short slow motion effect when the boss transforms or breaks down.
- Use a Game Manager to set score or complete/end game
- HP Control can be used to change the player HP. You can use it with an ID field to heal the player when walking near it.
- Emitter or Multi-emitter can be used to spawn mini adds during the boss fight.
- Event Listener can detect when the player dies and then recharge the boss HP for example.
- SFX Emitter can be used for different sound effects.
