Controller/gamepad support in Unity - Step-by-Step Execution

Concept Flow - Controller/gamepad support

Start Game

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Initialize Input System

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Detect Connected Controllers

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Read Controller Input

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Map Input to Actions

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Update Game State

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Render Frame

↩Back to Read Controller Input

The game starts by initializing the input system, detecting controllers, reading their input, mapping inputs to game actions, updating the game state, and rendering frames in a loop.

Execution Sample

Unity

void Update() {
  float moveX = Input.GetAxis("Horizontal");
  float moveY = Input.GetAxis("Vertical");
  Vector3 move = new Vector3(moveX, 0, moveY);
  transform.Translate(move * speed * Time.deltaTime);
}

This code reads the horizontal and vertical axes from a controller and moves the player accordingly each frame.

Execution Table

Frame	Input.GetAxis("Horizontal")	Input.GetAxis("Vertical")	Move Vector	Action Taken
1	0.0	0.0	(0.0, 0, 0.0)	No movement
2	0.5	0.0	(0.5, 0, 0.0)	Move right
3	0.5	0.7	(0.5, 0, 0.7)	Move diagonally forward-right
4	0.0	-1.0	(0.0, 0, -1.0)	Move backward
5	0.0	0.0	(0.0, 0, 0.0)	No movement

💡 Loop continues every frame reading input and moving player accordingly.

Variable Tracker

Variable	Start	After Frame 1	After Frame 2	After Frame 3	After Frame 4	After Frame 5
moveX	0.0	0.0	0.5	0.5	0.0	0.0
moveY	0.0	0.0	0.0	0.7	-1.0	0.0
move	(0,0,0)	(0,0,0)	(0.5,0,0)	(0.5,0,0.7)	(0,0,-1)	(0,0,0)

Key Moments - 3 Insights

Why does moveX sometimes have values between -1 and 1 instead of just -1, 0, or 1?

Input.GetAxis returns a smooth value between -1 and 1 to allow gradual movement, as shown in the execution_table rows 2 and 3 where moveX is 0.5.

What happens if no controller is connected?

Input.GetAxis returns 0, so move vector is zero and the player does not move, as seen in frame 1 and 5 in the execution_table.

Why do we multiply by Time.deltaTime when moving the player?

Multiplying by Time.deltaTime makes movement smooth and frame-rate independent, ensuring consistent speed across frames.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of moveY at Frame 3?

A 0.7

B 0.0

C -1.0

D 0.5

💡 Hint

Check the 'Input.GetAxis("Vertical")' column at Frame 3 in the execution_table.

At which frame does the player move diagonally forward-right?

A Frame 1

B Frame 3

C Frame 2

D Frame 4

💡 Hint

Look at the 'Action Taken' column in the execution_table for the diagonal movement description.

If the controller is disconnected, what would Input.GetAxis return and how would the player move?

A Returns -1, player moves backward

B Returns 1, player moves forward

C Returns 0, player does not move

D Returns random values, player moves erratically

💡 Hint

Refer to the explanation in key_moments about no controller connected and frame 1 and 5 in execution_table.

Concept Snapshot

Unity controller support uses Input.GetAxis to read controller sticks.
Values range from -1 to 1 for smooth movement.
Multiply movement by Time.deltaTime for smooth frame-rate independent motion.
Check for controller connection; no input means zero movement.
Update player position each frame in Update() method.

Full Transcript

This visual execution shows how Unity reads controller input each frame using Input.GetAxis for horizontal and vertical axes. The values range smoothly between -1 and 1, allowing gradual movement. The move vector is calculated from these inputs and multiplied by speed and Time.deltaTime to move the player smoothly and consistently regardless of frame rate. The execution table traces input values and resulting movement actions frame by frame. Key moments clarify why input values are smooth floats, what happens if no controller is connected, and why Time.deltaTime is used. The quiz tests understanding of input values and movement behavior. This helps beginners see how controller input drives player movement in Unity.