how to get the velocity Vector3 from global to local?

Question

Hi, I've been searching for hours but cant find the answer i'm looking for.

I have an enemy that jumps, i want him to jump forward based on his own forward vector but when I try to convert it to local space it doesn't work he jumps based on the forward vector of the global space.

 Vector3 Jump()
     {
 
         float intialvY = 60;
         float intialVx = 500;//350
         gravity.y = -9.8f;
 
         if(jumpToSteal == true)
         {
           myTransform.position += velocity * moveSpeed * Time.fixedDeltaTime;
 
             float tempVel = myTransform.InverseTransformDirection (velocity).z
   
             tempVel = intialVx * Time.deltaTime;
             velocity.y = ((intialvY) - (-gravity.y * timeTaken * 10)) * 20 * Time.deltaTime;
 
         }
 
         return velocity;
     }

I tried to use inverseDirection to change the z axis from global to local but then he only jumps straight up and doesn't move forward. The jumping works fine its just the forward direction that needs fixing. I also tried "Velocity = myTransform.forward" But that doesn't work either which is weird because its what i am using to move the enemy in its forward direction in a different function. Thanks for the help!

Answer 1

Best Answer

Answer by someGamer2 · Jun 27, 2017 at 10:56 PM

Took a while but I figured it out, for any future readers who want to be able to jump forward on the local axis for a gameobject.

 float intialvY = 60;//60;
 float intialVx = 500;//350
 float horizontalJump;
 float verticalJump;
 void Jump()
 {
     gravity.y = -9.8
     if(jumpToSteal == true)
     {
             fallSpeed = .2f;

             velocity = myTransform.TransformDirection (new Vector3(0, verticalJump, horizontalJump));//this line solved the problem


         myTransform.position += velocity * fallSpeed * Time.fixedDeltaTime;
   
         timeTaken += Time.deltaTime;
         verticalJump = ((intialvY) - (-gravity.y * timeTaken * 11)) * 20 * Time.fixedDeltaTime;
 
         horizontalJump = intialVx * Time.fixedDeltaTime;
 
         velocity = new Vector3 (0, verticalJump, horizontalJump);
         Debug.Log (velocity.z);
     }
 }//end of Jump()

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Answer 2

Answer by Rickyinjp · Jun 24, 2017 at 08:26 PM

So I think an easy way would be to use

 transform.forward

so if you want to move a certain speed in the direction you're facing, do

 rigidbody.velocity = speed*transform.forward; // If you're using the physics engine. This should be in FixedUpdate()
 
 
 transform.position += speed*transform.forward*Time.deltaTime;
 // The above is if you're not using physics engine but it's naughty. It's not recommended to directly change the transform position.
 
 
 // Use Translate instead if there's no physics engine. Translate uses local axes.
 transform.Translate(Vector3.forward*speed*Time.deltaTime);

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Answer 3

Answer by DroidifyDevs · Jun 24, 2017 at 04:30 PM

Global vectors will start with Vector3; for example Vector3.forward. Local vectors will look like this: YourGameObject.transform.forward.

Take a look at this: https://docs.unity3d.com/ScriptReference/Transform-forward.html

So in your code, try in line 12 myTransform.forward

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someGamer2 · Jun 25, 2017 at 12:24 AM 0

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I tried that but now the model doesn't push forward when his jumps, he jumps straight.

how to get the velocity Vector3 from global to local?

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