Unity Tanks Tutorial

Concepts Learned In Each Phase

Index

1. Scene Setup
2. Tank Creation & Control
3. Camera Control
4. Tank Control
5. Shell Creation
6. Firing Shells
7. Game Managers
8. Audio Mixing

01. Scene Setup

Basic scene setup

General

• Dragging asset models into the scene or hierarchy
• Frame selecting game objects in scene: dbl-click game object in Hierarchy, or 'F' key in Scene when selected

Lighting

• Dedicated window for lighting options
• Precomputed Real Time GI selected for use
  • Baking the lighting (a lengthy bg process)
  • Low resolution OK for lowpoly models
• Ambient light source & color vs. skybox

02. Tank Creation & Control

How to add the tank artwork and components to let the player control the tank.

General

• Layers
  • For collider interaction isolation
  • Only collider owner needs to be on layer (parent GO, not children)
• Duplication of GameObjects (Ctrl+D or right-click context menu)
• Project Settings
  • Input Manager: configuring input control & names

Components

• Component adding, setup, & collapsing
  • Rigidbody
    • req'd for Physics system
    • constraints on axes (position/rotation)
    • Kinematics: turn on/off (receive physical forces/no forces)
  • Colliders (primitive)
    • reports physics events (collisions) to Rigidbody
    • Trigger vs. Physical events
    • proper sizing for model
  • Audio Source
    • Populating references using "Circle Select" in Inspector
    • versus dragging from Project Assets folders
    • Empty references to be populated at runtime via scripting
  • Scripts
    • are also Components (provided they extend from Monobehaviour)

Prefabs

• Dragging configured scene objects from Hierarchy into Project Prefabs folder
  • and vice versa
• Prefab options: Select, Revert, Apply
  • between prefab & scene object linkage
  • Applying changes from changed Hierarchy/Scene game objects to prefabs.
  • Blue vs gray text in Hierarchy: Saved vs. unsaved changes to prefabs from scene gameobjects
    • Also bold fields in Inspector are unsaved changes to prefabs

Particle Systems

• World vs. Local simulation space
• Simulate over time vs. distance
• Various options for behavior

Scripting

• Script editing, compiling, serializing workflow in Unity
• Console window messages for debugging.
• Public vs. Private fields/member variables
  • relation to Inspector view (public fields show up for editing & populating references)
  • UnassignedReferenceExceptions when forgetting to assign reference in Inspector panel.
• Inspector serialized values override values assigned in the script's public/serializable variables.
• Dynamically referencing & manipulating Components at runtime
• Variable naming conventions
  • e.g. m_Name denotes class member variable (scoping mnemonic)
• TankMovement (inherits from MonoBehavior)
  • Script Component for Tank GameObject to control its movement
  • coding MonoBehaviour Event methods (Awake, Start, Update, etc)
• Vector manipulation math for Rigidbody movement by applying forces via method calls
• Quaternion representation in Unity for rotations of Transformations
  • Quaternion.Euler() method for easy Euler angle conversions

03. Camera Control

How to create a Camera rig which pans and zooms to keep all tanks on-screen at once.

• Creation of an empty GameObject called CameraRig to house a Script Component: CameraControl.cs
• Rig becomes parent of the existing MainCamera
• Scripted to keep both tanks in view: Pan and Zoom (i.e. move & resize frustum)
  • Tanks will stay in camera's frustum: area b/w near & far clip plane
  • Perspective frustum: variable size clip planes
  • Orthographic frustum: same size clip planes, hence no change in scale over distance
  • Orthographic Camera size in relation to aspect ratio (16:9) & aspect (1.77).
• GameObject.GetComponentInChildren() method OK if child component type is unique.
• [HideInInspector] attribute to prevent public member from being serialized to Inspector.

04. Tank Health

Setup tank damage, update UI heal slider based on health value, tank deactivation on death

• Using a Unity UI Slider as a radial health bar.
• UI Elements: Canvas, Slider, EventSystem
• EventSystem Input Module component in Inspector
  • Axis setup along with InputManager
• Canvas Scaler (Script) component for helping developing multiresolution apps
• Canvas component Render modes: Screenspace vs. Worldspace
• Rect Transform component in all UI elements.
• Anchor presets button to edit anchors (Shift/Alt)
• Top to Bottom rendering of UI child elements of Canvas (as found in the Hierarchy)
• Instantiating inactive game objects (e.g. particle systems) to cache them until ready for use.
  • Also, setting them inactive again instead of destroying them then reinstantiating again.
  • Caching like this (inactive->active) saves on garbage collection calls.

05. Shell Creation

Create a ballistic shell for the tank & a radius for explosion forces

• Collider triggers for simply creating callbacks in scripts to react to, instead of physical forces.
• Physics.OverlapSphere(pos,radius,layer) method to get an array of colliders touching/inside a specified sphere.
• Rigidbody.AddExplosionForce(force,pos,radius) to simulate explosive forces.
• Component references can also be used to get other component references on same GameObject via GetComponent<>().

06. Firing Shells

How to fire projectiles, and make a UI & sound effect to accompany the mechanic.

• Re-appropriate a UI Slider to make an aiming guide.
• Shells are unoptimally instantiated and destroyed every fire. Object pooling pattern would solve this.

07. Game Managers

Game loop architecture using coroutines and textual UI creation for messaging players.

• Text UI GameObject creation and usage, along with Shadow script component for effect.
• [Serializable] attribute on classes are serialized for view in the Inspector.
• ColorUtility.ToHtmlStringRGB(Color) for converting an rgb color to HTML code for rich text.
• Coroutines are used to cleverly manage the main game loop.

Coroutines

• A function that can suspend its execution (yield) until the given YieldInstruction finishes.
• Normal coroutine updates are run after the Update() function returns.
• Can be used as a way to spread an effect over a period time
• It is also a useful optimization since it also allows you to determine at what rate any function gets called.

Return types & different uses of Coroutines:

yield                       // The coroutine will continue after all Update functions have been called on the next frame.
yield WaitForSeconds        // Continue after a specified time delay, after all Update functions have been called for the frame
yield WaitForFixedUpdate    // Continue after all FixedUpdate has been called on all scripts
yield WaitForEndOfFrame     // Continue after all FixedUpdate has been called on all scripts
yield WWW                   // Continue after a WWW download has completed.
yield StartCoroutine        // Chains the coroutine, and will wait for the MyFunc coroutine to complete first.

Coroutines also admit a nice, slick, readable game loop:

void Start() {
    // ... other start code ...
    StartCoroutine (GameLoop()); // Let's play!
}

// This is called from start and will run each phase of the game one after another.
private IEnumerator GameLoop() {
    yield return StartCoroutine (LevelStart()); // Start the level: Initialize, do some fun GUI stuff, ..., WaitForSeconds if setup too fast.
    yield return StartCoroutine (LevelPlay());  // Let the user(s) play the level until a win or game over condition is met, then return back here.
    yield return StartCoroutine (LevelEnd());   // Find out if some user(s) "won" the level or not. Also, do some cleanup.
    
    if (WinCondition) { // Check if game level progression conditions were met.
        Application.LoadLevel(++level); // or Application.LoadLevel(Application.loadedLevel) if using same scene
    } else { // Let the user retry the level by restarting this (non-yielding) coroutine again.
        StartCoroutine (GameLoop());
    }
}

08. Audio Mixing

Balance the audio in the game with a dynamic mix where sound effects duck the volume of the music.

• A MainMix audio mixer default is created that outputs directly to the AudioListener.
• Audio Mixer window is used to create 3 additional Audio Mixer Groups: Music, SFX, Driving.
  • Used to modify/mix the audio output before reaching the AudioListener.
• Audio Source components (in our Prefabs) are setup to output their clips through the Audio Mixer Groups.
  • Default setup was to output clips straight to the AudioListener, without mixing.
• A "Duck Volume" effect is then used to lower the bg music when sfx are playing.
  • The SFX group is setup to "Send Effect" its signal to the Music group's "Duck Volume" effect.