Unity3D

Basic Skills

• Usually set the values of private values in the Start() function.
• Only gameObject has the function of GetComponent
• Transform
  • Only transform has the function of Find(string name)
  • The function of Find(string name) for a transform can only find the direct children of a transform

Physics Engine

Collider

Wheel Collider

Wheel collider is a collider rather than the mesh of the wheel. You can add force or torque to the collider to make the collider rotate like a wheel.

Rigidbody

Rigidbody has a element named velocity, which can set the speed(Vector3) of the gameobject.

Detect collision or collision position between objects

• Use OnCollisionEnter or OnTriggerEnter
  • Required object to have collider and rigidbody
• Use Physics.OverlapSphere(point) to detect whether the point collides with other colliders.
• Use Collider.Raycast to get the accurate collision position. It will ignore other colliders but this collider.

Scripting

Find Objects

• Use transform.root.gameObject can find the root object
• Use gameObject.GetComponentInChild() can find the script attached to the child objects.
• Use transform.Find() can find the children objects, but this is only used to find the direct children objects.

Attributes

Attributes of C# can add metadata (information about the types defined in a program) to the program. In Unity, it can be used to show information in Unity editor’s inspector.

The attributes work by placing the name of the attribute enclosed in square brackets ([]) above the declaration of the entity to which it applies. There are several different attributes in Unity

Name	Function
HideInInspector	Hide public parameter in Unity Inspector
SerializeField	Show the private parameter in Unity Inspector
Space	Show a space line in Unity Inspector
Header(“XX”)	Show a comment for the parameter in Unity Inspector
Range(min, max)	Show the value range in Unity Inspector

Asynchronous

Unity can use async/await keywords of C# to achieve asynchronous methods, which can be found here.

However, some Unity library functions cannot be executed correctly in the asynchronous thread. Instead, Unity has its own asynchronous keyword, which is IEnumerator/yield return.

yield return keyword has many kinds of return type, which shows following

Type	Function
yield return new WaitForEndofFrame()	Wait until the end of current frame
yield return new WaitForFixedFrame()	Wait until next frame
yield return new WaitForSeconds(xx)	Wait for xx seconds
yield return new WaitForWhile(func)	Wait until func return false
yield return new WaitForUntil(func)	Wait until func return true

In Unity scripts, sometimes we need to do some actions after changing the properties of the GameObject, e.g. position, rotation. Unity will finish the changing action in the end of current frame. So we need to wait for a while before doing other actions.

Note. the event of delegate trigger is also finished in the current frame.

Also in Unity, we need to use yield return null or allow the code return to the main thread to do some changes in the scene.

Note. don’t use yield return 0 because it is the same with yield return null but it will lead to boxing action.

Compile

Conditional Compile

Unity has many targeted platforms, so the codes can be conditional complied according to this link

Compile Pipeline

• Unity will compile C# scripts to IL with C# compiler firstly
• Unity will also combines all the other assemblies like the UnityEngine.dll and mscorlib.dll
• Unity will use Mono or IL2CPP to build the IL scripts to naive code