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How to calculate a GameObject's speed in Unity?

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0

I have tried something like

float speed = (currentPosition - previousPosition).magnitude / Time.deltaTime

in Update().

But I get very bad results because currentPosition and previousPosition are too close. After subtraction there's too much rounding error. The speed values fluctuate too much.

And also I don't want to average across multiple frames because that produces delays and only improves the result a little.

Is there any better way to calculate the speed of an object?

unity3d

share|improve this question

asked Mar 7 at 11:44

landingslandings

847

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Calculate per second and update with linearly interpolates.
  
  – shingo
  Mar 7 at 11:57
  

  
  
  
  

add a comment | 

0

I have tried something like

float speed = (currentPosition - previousPosition).magnitude / Time.deltaTime

in Update().

But I get very bad results because currentPosition and previousPosition are too close. After subtraction there's too much rounding error. The speed values fluctuate too much.

And also I don't want to average across multiple frames because that produces delays and only improves the result a little.

Is there any better way to calculate the speed of an object?

unity3d

share|improve this question

asked Mar 7 at 11:44

landingslandings

847

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Calculate per second and update with linearly interpolates.
  
  – shingo
  Mar 7 at 11:57
  

  
  
  
  

add a comment | 

I have tried something like

float speed = (currentPosition - previousPosition).magnitude / Time.deltaTime

in Update().

But I get very bad results because currentPosition and previousPosition are too close. After subtraction there's too much rounding error. The speed values fluctuate too much.

And also I don't want to average across multiple frames because that produces delays and only improves the result a little.

Is there any better way to calculate the speed of an object?

unity3d

share|improve this question

asked Mar 7 at 11:44

landingslandings

847

share|improve this question

asked Mar 7 at 11:44

landingslandings

847

share|improve this question

asked Mar 7 at 11:44

landingslandings

847

asked Mar 7 at 11:44

landingslandings

847

asked Mar 7 at 11:44

landingslandings

847

1 Answer
1

active

oldest

votes

1

You could use a coroutine that calculates the speed slower than every frame:

void OnEnabled() 
 StartCoroutine(SpeedReckoner());


public float Speed;
public float UpdateDelay;

private IEnumerator SpeedReckoner() 

 YieldInstruction timedWait = new WaitForSeconds(UpdateDelay);
 Vector3 lastPosition = transform.position;
 float lastTimestamp = Time.time;

 while (enabled) 
 yield return timedWait;

 var deltaPosition = (transform.position - lastPosition).magnitude;
 var deltaTime = Time.time - lastTimestamp;

 if (Mathf.Approximately(deltaPosition, 0f)) // Clean up "near-zero" displacement
 deltaPosition = 0f;

 Speed = deltaPosition / deltaTime;


 lastPosition = transform.position;
 lastTimestamp = Time.time;
 

share|improve this answer

answered Mar 7 at 12:45

ImmersiveImmersive

84049

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Your answer is very helpful. Thank you.
  
  – landings
  Mar 8 at 5:40
  

  
  
  
  

add a comment | 

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1

You could use a coroutine that calculates the speed slower than every frame:

void OnEnabled() 
 StartCoroutine(SpeedReckoner());


public float Speed;
public float UpdateDelay;

private IEnumerator SpeedReckoner() 

 YieldInstruction timedWait = new WaitForSeconds(UpdateDelay);
 Vector3 lastPosition = transform.position;
 float lastTimestamp = Time.time;

 while (enabled) 
 yield return timedWait;

 var deltaPosition = (transform.position - lastPosition).magnitude;
 var deltaTime = Time.time - lastTimestamp;

 if (Mathf.Approximately(deltaPosition, 0f)) // Clean up "near-zero" displacement
 deltaPosition = 0f;

 Speed = deltaPosition / deltaTime;


 lastPosition = transform.position;
 lastTimestamp = Time.time;
 

share|improve this answer

answered Mar 7 at 12:45

ImmersiveImmersive

84049

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Your answer is very helpful. Thank you.
  
  – landings
  Mar 8 at 5:40
  

  
  
  
  

add a comment | 

1

You could use a coroutine that calculates the speed slower than every frame:

void OnEnabled() 
 StartCoroutine(SpeedReckoner());


public float Speed;
public float UpdateDelay;

private IEnumerator SpeedReckoner() 

 YieldInstruction timedWait = new WaitForSeconds(UpdateDelay);
 Vector3 lastPosition = transform.position;
 float lastTimestamp = Time.time;

 while (enabled) 
 yield return timedWait;

 var deltaPosition = (transform.position - lastPosition).magnitude;
 var deltaTime = Time.time - lastTimestamp;

 if (Mathf.Approximately(deltaPosition, 0f)) // Clean up "near-zero" displacement
 deltaPosition = 0f;

 Speed = deltaPosition / deltaTime;


 lastPosition = transform.position;
 lastTimestamp = Time.time;
 

share|improve this answer

answered Mar 7 at 12:45

ImmersiveImmersive

84049

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Your answer is very helpful. Thank you.
  
  – landings
  Mar 8 at 5:40
  

  
  
  
  

add a comment | 

You could use a coroutine that calculates the speed slower than every frame:

void OnEnabled() 
 StartCoroutine(SpeedReckoner());


public float Speed;
public float UpdateDelay;

private IEnumerator SpeedReckoner() 

 YieldInstruction timedWait = new WaitForSeconds(UpdateDelay);
 Vector3 lastPosition = transform.position;
 float lastTimestamp = Time.time;

 while (enabled) 
 yield return timedWait;

 var deltaPosition = (transform.position - lastPosition).magnitude;
 var deltaTime = Time.time - lastTimestamp;

 if (Mathf.Approximately(deltaPosition, 0f)) // Clean up "near-zero" displacement
 deltaPosition = 0f;

 Speed = deltaPosition / deltaTime;


 lastPosition = transform.position;
 lastTimestamp = Time.time;
 

share|improve this answer

answered Mar 7 at 12:45

ImmersiveImmersive

84049

void OnEnabled() 
 StartCoroutine(SpeedReckoner());


public float Speed;
public float UpdateDelay;

private IEnumerator SpeedReckoner() 

 YieldInstruction timedWait = new WaitForSeconds(UpdateDelay);
 Vector3 lastPosition = transform.position;
 float lastTimestamp = Time.time;

 while (enabled) 
 yield return timedWait;

 var deltaPosition = (transform.position - lastPosition).magnitude;
 var deltaTime = Time.time - lastTimestamp;

 if (Mathf.Approximately(deltaPosition, 0f)) // Clean up "near-zero" displacement
 deltaPosition = 0f;

 Speed = deltaPosition / deltaTime;


 lastPosition = transform.position;
 lastTimestamp = Time.time;
 

share|improve this answer

answered Mar 7 at 12:45

ImmersiveImmersive

84049

answered Mar 7 at 12:45

ImmersiveImmersive

84049

answered Mar 7 at 12:45

ImmersiveImmersive

84049