In this post, we’ll create a simple script to manage player health, then use that script and Unity triggers to create health pickups and environmental danger (lava) in a level.
Before we get started on our health scripts, let’s create a prototype 3D environment to test them in. Create a new project with a new scene. Save this as “LavaWorld”.
Begin by adding two textures to the project, a tileable rock texture and a tileable lava texture. If you don’t have those assets already, there are many sources of free textures online. Click Here is a good start.
Create two new Materials named “LavaMaterial” and “RockMaterial” to match the new textures by right-clicking in the Project pane and selecting Create > Material. Drag the rock texture into the Albedo slot of RockMaterial. Drag the lava texture into the Emission slot of LavaMaterial to create a glowing lava effect. Now our materials are ready to use.
In the Hierarchy view, use Create > 3D Object > Cube to create a 3D cube in the scene.
Drag RockMaterial into the Materials > Element 0 slot on the Mesh Renderer of your cube in order to change the cube texture from the default blue material to your rock texture.
Use the scale controls to stretch and flatten the cube. We now have a simple “rock platform”. Copy and paste the platform a few times, moving the new copies away to form small “islands”. Create a few more copies of the rock platform, scale them so that they’re long and thin, and position them as bridges between the “islands”. For example:
Now, create a new cube named “LavaVolume”, and assign it the LavaMaterial. Scale it so that it is large enough to encompass all the islands but shallow (scale the y-axis height down). Move it so that it is lower than the islands, and so they appear to float in a lava field.
In order to make it possible that a player can fall into the lava, check the BoxCollider’s “Is Trigger” property on LavaVolume. The Box Collider will now act as a Trigger volume, no longer physically blocking objects that come into contact with it, but notifying the script when an object moves through the collider volume.
This presents a problem, as objects will now fall through the lava into infinite space!
To deal with this problem, make another copy of the rock platforms and scale/position it so that it’s a similar dimension to the lava, also wide but flat, and position it just below the lava. So it forms a rock “floor” under the lava volume.
To make your scene a little nicer, repeat the process to create rock walls around the lava, hiding where the lava volume ends. A few point lights ( Create > Light > Point Light) scattered around the islands will also add interesting visual variety.
Now it’s time to add a player!
First, import the “Standard Assets” package from the Unity Asset Store (if you don’t know how to do this, google the Unity Asset Store to learn about it).
In the newly imported Standard Assets Project folder, go to Characters > FirstPersonCharacter > Prefabs. There you will find the FPSController prefab. Drag it into your scene, rename it to “Player” and position it on one of the islands, like so:
Delete the old main camera that you had in your scene; the FPSController has its own camera.
If you run the project, you should be able to walk around your scene, from island to island. You can also walk in the lava, but it doesn’t harm you, yet.
To make the lava an actual threat, we start by giving our player the ability to track its health. In the Project Pane, right-click and select Create > C# Script. Name the script “Player”. Drag the Player script onto the Player object in the Hierarchy view.
Open the script in Visual Studio, and add code as follows:
This script exposes a variable, maxHealth, which determines how much health the Player starts with and the maximum health they can ever have. It exposes a function to alter the Player’s current health. And it uses a reference to a Text object to display the Player’s current health on screen.
Back to Unity, you can now see the Max Health Property exposed in the inspector. Set Max Health to 100. There is also a field for Current Health Label, but we don’t currently have a GUI.
To remedy this, in the Hierarchy view, select Create > UI > Canvas and then Create > UI > Label. This will create the UI root and a text label on it. Change the label’s text to “Health:”, the font size to 20 and colour to white. Drag it to the bottom left corner of the screen (and make sure the Rect Transform anchor is set to bottom left).
Duplicate that text label, offset it right a little from the previous text label and change the text to “0”. Rename this new label “CurrentHealthLabel”. The GUI should now look like this:
In the Hierarchy view, drag CurrentHealthLabel into your Player script’s “Current Health Label” property.
If we run now, we’ll have a display in the bottom corner of the screen showing our Player’s health of 100.
By itself, this isn’t particularly exciting. Time to add lava!
Create a new c# script as before; call it Lava. Add this Lava script to the LavaVolume scene object. Open the script in Visual Studio and insert the following code:
Note the TriggerEnter and TriggerExit functions. Because LavaVolume, the object we’ve added this script to, has a collider with Is Trigger checked, whenever another object enters LavaVolume’s box collider, OnTriggerEnter will be called, with the colliding object’s Collider passed as a parameter. Similarly, when an object leaves LavaVolume’s collider volume, OnTriggerExit will be called.
Taking advantage of this functionality, we keep a list of all players who enter the lava. Then, during the Update call, if any players are in the lava, we apply damage to them periodically. damageTickTime determines an interval between every time we apply damage (a “tick”), and damagePerTick determines how much damage we apply per tick. Both properties are exposed in the Inspector by the script, so that they’re customizable. Set the values to Damage Per Tick = 5 and Damage Tick Time = 0.1.
Now, if we run the game, stepping in the lava hurts! But, it’s a bit of an anti-climax, since nothing actually happens when our health gets down to 0.
Let’s make things a little more fatal.
First, use a paint program to create a “You Died!” screen at 1920 x 1080 resolution.
Add that image to the project. Under the Import Settings, set the Texture Type to Sprite (2D and UI). Then, from the Hierarchy, select Create > UI > Image. Make the size 1920 x 1080, and set the Source Image property to your new player died sprite image.
Go back to your Player Script and extend the code as follows:
The additions add a reference to the player died screen, and code in the CheckDead function to check if the player’s health reaches 0, displaying the death screen if it does. The function also disables the FirstPersonController script if the player dies, so that the player can’t continue to move Player around via keyboard/mouse input after Player has died.
Return to the Hierarchy view, and drag the player died screen into the exposed Dead Screen property on the Player script.
Now, if you run the game, stepping in lava will “kill” the player if they stay in it long enough. Better!
But it’s only fair to add a way for the Player to recover health, too. To do so, use a paint program to create a new “medkit” texture.
Following the same procedure as used to create the LavaVolume, create a new cube called HealthKit, give it a Material that uses this new medkit texture, and enable “Is Trigger” on the cube’s BoxCollider.
Create a new C# script called “Health Pickup”, add it to the cube, and insert the following code:
Simpler than the Lava script, this adds health to a Player that collides with it, before disabling itself.
Scale the HealthKit object until it looks about the right size for a health pack; then copy and paste a few of the packs across the islands. Now, when you play, if you manage to extricate yourself from the lava after falling in, you can collect a health pack to restore your health!
And that brings us to the end of the Simple Player Health tutorial. We have a deadly lava level with health pickups, just waiting for enemy characters to be added.
About the author
Gareth Fouche is a game developer. He can be found on Github at @GarethNN