Documentation

Unity Engine

User Manual

Script Reference

Unity Engine

deltaTime

The interval in seconds from the last frame to the current one (Read Only).
Read time 3 minutesLast updated 6 days ago

Definition

  • Type: Property
  • Namespace: UnityEngine
  • Assembly: UnityEngine.CoreModule
public static float deltaTime { get; }

Remarks

When called from inside MonoBehaviour.FixedUpdate() or anywhere in the Physics update loop, including coroutines that yield WaitForFixedUpdate, 
deltaTime
returns Time.fixedDeltaTime. The maximum value for 
deltaTime
is defined by Time.maximumDeltaTime.
The value 
deltaTime
is scaled according to Time.timeScale. If the game is paused by setting Time.timeScale to 
0
, then 
deltaTime
also becomes 
0
. The first frames after changing Time.timeScale can produce unexpected 
deltaTime
values. Use Time.unscaledDeltaTime instead if you need wall-clock time during pause.
The value of 
deltaTime
can be unreliable in callbacks that might be invoked multiple times per frame, such as MonoBehaviour.OnGUI() or UI layout or repaint events.
The first frame 
Update
can produce a very small or zero 
deltaTime
on some platforms, as can the first frame after a domain and scene reload.
Depending on the platform and the Application.runInBackground setting, when the application loses focus or is in the background, 
Update
might be called infrequently or with long gaps, producing large 
deltaTime
values.
The following example rotates a GameObject around its z axis at a constant speed.
For more information on how this property relates to the other time properties, refer to Time and Frame Rate Management in the Unity manual.
using UnityEngine;// Rotate around the z axis at a constant speedpublic class ConstantRotation : MonoBehaviour{    public float degreesPerSecond = 2.0f;    void Update()    {        transform.Rotate(0, 0, degreesPerSecond * Time.deltaTime);    }}
The following example implements a timer. The timer adds deltaTime each frame. The example displays the timer value and resets it when it reaches 2 seconds. Time.timeScale controls the speed at which time passes and how fast the timer resets.
using System.Collections;using System.Collections.Generic;using UnityEngine;// Time.deltaTime example.//// Wait two seconds and display waited time.// This is typically just beyond 2 seconds.// Allow the speed of the time to be increased or decreased.// It can range between 0.5 and 2.0. These changes only// happen when the timer restarts.public class ScriptExample : MonoBehaviour{    private float waitTime = 2.0f;    private float timer = 0.0f;    private float visualTime = 0.0f;    private int width, height;    private float value = 10.0f;    private float scrollBar = 1.0f;    void Awake()    {        width = Screen.width;        height = Screen.height;        Time.timeScale = scrollBar;    }    void Update()    {        timer += Time.deltaTime;        // Check if we have reached beyond 2 seconds.        // Subtracting two is more accurate over time than resetting to zero.        if (timer > waitTime)        {            visualTime = timer;            // Remove the recorded 2 seconds.            timer = timer - waitTime;            Time.timeScale = scrollBar;        }    }    void OnGUI()    {        GUIStyle sliderDetails = new GUIStyle(GUI.skin.GetStyle("horizontalSlider"));        GUIStyle sliderThumbDetails = new GUIStyle(GUI.skin.GetStyle("horizontalSliderThumb"));        GUIStyle labelDetails = new GUIStyle(GUI.skin.GetStyle("label"));        // Set the size of the fonts and the width/height of the slider.        labelDetails.fontSize = 6 * (width / 200);        sliderDetails.fixedHeight = height / 32;        sliderDetails.fontSize = 12 * (width / 200);        sliderThumbDetails.fixedHeight = height / 32;        sliderThumbDetails.fixedWidth = width / 32;        // Show the slider. Make the scale to be ten times bigger than the needed size.        value = GUI.HorizontalSlider(new Rect(width / 8, height / 4, width - (4 * width / 8), height - (2 * height / 4)),            value, 5.0f, 20.0f, sliderDetails, sliderThumbDetails);        // Show the value from the slider. Make sure that 0.5, 0.6... 1.9, 2.0 are shown.        float v = ((float)Mathf.RoundToInt(value)) / 10.0f;        GUI.Label(new Rect(width / 8, height / 3.25f, width - (2 * width / 8), height - (2 * height / 4)),            "timeScale: " + v.ToString("f1"), labelDetails);        scrollBar = v;        // Display the recorded time in a certain size.        labelDetails.fontSize = 14 * (width / 200);        GUI.Label(new Rect(width / 8, height / 2, width - (2 * width / 8), height - (2 * height / 4)),            "Timer value is: " + visualTime.ToString("f4") + " seconds.", labelDetails);    }}