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I have a sci-fi themed tank that I need to make it look like it's hovering up and down through C# script. How do I go about applying force to the rigidbody giving it the impression that it's hovering up and letting gravity bring it back down again all without increasing or editing the collider box? Where do I start?

EDIT

So I was playing around with the code I gave in the link below to see if it was an all in one solution and I think my freak of nature gravity value (-500) is affecting the code badly and my craft still sticks to the ground does anyone have a clue?

Converted Code:

using UnityEngine;

using System.Collections;

public class ScifiHover : MonoBehaviour { float forwardPower;

float steerPower;

float landingPower;

float jumpingPower;

float hoverHeight;

float stability = 1;

public GameObject body;


public float speedUpdate;


private Vector3[] hitNormal = new Vector3[5];

private Quaternion rotation;

private float increment;

private Vector3[] lastNormals = new Vector3[5];

private bool physicsSetup = false;

private Vector3 boxDim;

private Vector3[] cornersPoint = new Vector3[5];

private Transform[] corners = new Transform[5];

private BoxCollider boxCollider;

private float yBounce;

private Vector3 lastPosition;

private float distance;

private Vector3 average;


void Awake()
{

    InitializePhysics();
}


void Update()
{

    CalculateSpeed();

}


void FixedUpdate()
{


    if (physicsSetup)
    {

        RaycastHit hit;


        for (int i = 0; i <= corners.Length - 1; i++)
        {

            if (Physics.Raycast(corners[i].position, -corners[i].up, out hit, hoverHeight + 100.0f))
            {

                if (hit.collider.gameObject.tag == "Floor")
                {

                    hitNormal[i] = body.transform.InverseTransformDirection(hit.normal);

                    if (lastNormals[i] != hitNormal[i])
                    {

                        increment = 0;

                        lastNormals[i] = hitNormal[i];

                    }

                    distance = hit.distance;

                    if (hit.distance < hoverHeight)
                    {

                        constantForce.relativeForce = (-average + transform.up) * rigidbody.mass * jumpingPower * rigidbody.drag * Mathf.Min(hoverHeight, hoverHeight / distance);

                    }
                    else
                    {

                        constantForce.relativeForce = -(transform.up) * rigidbody.mass * landingPower * rigidbody.drag / Mathf.Min(hoverHeight, hoverHeight / distance);

                    }

                }

            }

        }

        average = -(hitNormal[0] + hitNormal[1] + hitNormal[2] + hitNormal[3] + hitNormal[4]) / 2;


        if (increment != 1) { increment += 0.03f; }


        rotation = Quaternion.Slerp(body.transform.localRotation, Quaternion.Euler(average * Mathf.Rad2Deg), increment);


        Quaternion temp = rotation;

        temp.y = transform.up.y * Mathf.Deg2Rad;

        body.transform.localRotation = temp;


        float fwdForce = Input.GetAxis("Vertical") * forwardPower;

        rigidbody.AddForce(transform.forward * fwdForce);


        float steerForce = Input.GetAxis("Horizontal") * steerPower;

        rigidbody.AddTorque(transform.up * steerForce);


    }

}

void CalculateSpeed()
{

    if (lastPosition != transform.position)
    {

        float distance = Vector3.Distance(transform.position, lastPosition);

        speedUpdate = (distance / 1000) / (Time.deltaTime / 3600); //Km/h

    }

}


void InitializePhysics()
{

    //Store the box dimenssion of the hovering object.

    boxCollider = body.AddComponent<BoxCollider>();

    boxDim = new Vector3(boxCollider.size.x * body.transform.localScale.x, boxCollider.size.y * body.transform.localScale.y, boxCollider.size.z * body.transform.localScale.z) * stability;

    cornersPoint[0] = new Vector3(transform.position.x - boxDim.x / 2, transform.position.y - boxDim.y / 2, transform.position.z + boxDim.z / 2);

    cornersPoint[1] = new Vector3(boxDim.x / 2 + transform.position.x, transform.position.y - boxDim.y / 2, transform.position.z + boxDim.z / 2);

    cornersPoint[2] = new Vector3(boxDim.x / 2 + transform.position.x, transform.position.y - boxDim.y / 2, transform.position.z - boxDim.z / 2);

    cornersPoint[3] = new Vector3(transform.position.x - boxDim.x / 2, transform.position.y - boxDim.y / 2, transform.position.z - boxDim.z / 2);

    cornersPoint[4] = transform.position;

    Destroy(boxCollider);


    for (int i = 0; i <= cornersPoint.Length - 1; i++)
    {

        GameObject stablePlatform = GameObject.CreatePrimitive(PrimitiveType.Sphere);

        stablePlatform.name = "StablePlatform" + "(" + i + ")";

        stablePlatform.transform.parent = body.transform;

        stablePlatform.transform.localPosition = transform.InverseTransformPoint(cornersPoint[i]);

        corners[i] = stablePlatform.transform;

        Destroy(stablePlatform.GetComponent<MeshRenderer>());

        Destroy(stablePlatform.GetComponent<Collider>());

    }

    cornersPoint = null;

    physicsSetup = true;

}

}

Answer 1

Here's a part of my Hoverboard script.

What it does is check the distance down to the ground; if it is less than the specified height, it applies upward force at a percentage of the force needed to lift it up. The - Time.deltaTime is actually just a small number that is used to make sure the hoverForceMultiplier doesn't go above 1.

I have a Rigidbody of Mass 1, Use Gravity is Enabled (ticked).

EDIT - here's the C# version :

using UnityEngine;
using System.Collections;

public class HoverScript : MonoBehaviour 
{
    public float hoverDistance = 0.75f;
    public float hoverForce = 10.0f;
    private float currentHeight = 0.0f;
    private float hoverForceMultiplier = 0.0f;
    private Vector3 hoverForceApplied = Vector3.zero;

    void FixedUpdate() 
    {
        // -- find hover distance and add force to make hover   
        RaycastHit rayHit;
        if (Physics.Raycast(transform.position, Vector3.down, out rayHit))
        {
           currentHeight = rayHit.distance;
           if (currentHeight < (hoverDistance - Time.deltaTime))
           {
             // find percentage of currentHeight below hoverDistance
             hoverForceMultiplier = (hoverDistance - currentHeight) / hoverDistance;
             hoverForceApplied = (Vector3.up * hoverForce * hoverForceMultiplier) + (Vector3.up * 9.8f);
             rigidbody.AddForce(hoverForceApplied);         
           } else {       
             // apply anti-gravity force for half distance above hoverDistance
             if ((currentHeight - hoverDistance - Time.deltaTime) < (hoverDistance / 2))
             {
              hoverForceApplied = (Vector3.up * 9.8f) * ((hoverDistance - (currentHeight - hoverDistance)) / hoverDistance);
              rigidbody.AddForce(hoverForceApplied);
             }
           }
        }
    }
}

Original Post :

It's in JS and right now I have no time to convert and check it. I shall make a C# vesion when I get home tonight =]

#pragma strict

var hoverDistance : float = 0.75;
var hoverForce : float = 10.0;
private var currentHeight : float = 0.0;
private var hoverForceMultiplier : float = 0.0;
private var hoverForceApplied : Vector3 = Vector3(0, 0, 0);


function FixedUpdate () 
{
    // -- find hover distance and add force to make hover   
    var rayHit : RaycastHit;
    if(Physics.Raycast(transform.position, Vector3.down, rayHit))
    {
       currentHeight = rayHit.distance;
       if (currentHeight < (hoverDistance - Time.deltaTime))
       {
         // find percentage of currentHeight below hoverDistance
         hoverForceMultiplier = (hoverDistance - currentHeight) / hoverDistance;
         hoverForceApplied = (Vector3.up * hoverForce * hoverForceMultiplier) + (Vector3.up * 9.8);
         rigidbody.AddForce(hoverForceApplied);         
       } else {       
         // apply anti-gravity force for half distance above hoverDistance
         if ((currentHeight - hoverDistance - Time.deltaTime) < (hoverDistance / 2))
         {
          hoverForceApplied = (Vector3.up * 9.8) * ((hoverDistance - (currentHeight - hoverDistance)) / hoverDistance);
          rigidbody.AddForce(hoverForceApplied);
         }
       }
    }
}

example : http://www.alucardj.net16.net/unityquestions/HoverBoard6.html

Answer 2

0

As asafsitner mentioned, it's best to do it via animation, as it allows you to add unsteady hovering which also depends on the current state of the tank (i.e. moving, shooting, standing, searching).

You can always use Mathf.Cos or Mathf.Sin, as they will produce a periodical value which ranges from -1 to 1.

alt text

answered May 15 '12 at 12:35 PM

Tseng
1.5k ● 6 ● 8 ● 23

I would love to do it through animation however the current circumstance is not allowing me to do so and thus has to be done by script. I'm not too good with C# and unity so if you could help me get started on how to use Mathf.Cos or Mathf.Sin I would really appreaciate it.

What I'm trying to achieve is something like on this video (http://www.youtube.com/watch?v=JE0ZLq5bobc) however my controller and camera are all set I just simply need to make the tank hover up and down by time intervals.

May 16 '12 at 02:46 AM djdrool91

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