ForceMode.VelocityChange

Description

Add an instant velocity change to the rigidbody, ignoring its mass.

Apply the velocity change instantly with a single function call. In contrast to ForceMode.Impulse, VelocityChange will change the velocity of every rigidbody the same way regardless of differences in mass. This mode is useful for something like a fleet of differently-sized space ships that you want to control without accounting for differences in mass. In this mode, the unit of the force parameter is applied to the rigidbody as distance/time.

using UnityEngine;

public class ForceModeExample : MonoBehaviour
{
    //Use to switch between Force Modes
    enum ModeSwitching { Start, Impulse, Acceleration, Force, VelocityChange };
    ModeSwitching m_ModeSwitching;

    Vector3 m_StartPos, m_StartForce;
    Vector3 m_NewForce;
    Rigidbody m_Rigidbody;

    string m_ForceXString = string.Empty;
    string m_ForceYString = string.Empty;

    float m_ForceX, m_ForceY;
    float m_Result;


    void Start()
    {
        //You get the Rigidbody component you attach to the GameObject
        m_Rigidbody = GetComponent<Rigidbody>();

        //This starts at first mode (nothing happening yet)
        m_ModeSwitching = ModeSwitching.Start;

        //Initialising the force which is used on GameObject in various ways
        m_NewForce = new Vector3(-5.0f, 1.0f, 0.0f);

        //Initialising floats
        m_ForceX = 0;
        m_ForceY = 0;

        //The forces typed in from the text fields (the ones you can manipulate in Game view)
        m_ForceXString = "0";
        m_ForceYString = "0";

        //The GameObject's starting position and Rigidbody position
        m_StartPos = transform.position;
        m_StartForce = m_Rigidbody.transform.position;
    }

    void FixedUpdate()
    {
        //If the current mode is not the starting mode (or the GameObject is not reset), the force can change
        if (m_ModeSwitching != ModeSwitching.Start)
        {
            //The force changes depending what you input into the text fields
            m_NewForce = new Vector3(m_ForceX, m_ForceY, 0);
        }

        //Here, switching modes depend on button presses in the Game mode
        switch (m_ModeSwitching)
        {
            //This is the starting mode which resets the GameObject
            case ModeSwitching.Start:
                //This resets the GameObject and Rigidbody to their starting positions
                transform.position = m_StartPos;
                m_Rigidbody.transform.position = m_StartForce;

                //This resets the velocity of the Rigidbody
                m_Rigidbody.velocity = new Vector3(0f, 0f, 0f);
                break;

            //These are the modes ForceMode can force on a Rigidbody
            //This is Acceleration mode
            case ModeSwitching.Acceleration:
                //The function converts the text fields into floats and updates the Rigidbody’s force
                MakeCustomForce();

                //Use Acceleration as the force on the Rigidbody
                m_Rigidbody.AddForce(m_NewForce, ForceMode.Acceleration);
                break;

            //This is Force Mode, using a continuous force on the Rigidbody considering its mass
            case ModeSwitching.Force:
                //Converts the text fields into floats and updates the force applied to the Rigidbody
                MakeCustomForce();

                //Use Force as the force on GameObject’s Rigidbody
                m_Rigidbody.AddForce(m_NewForce, ForceMode.Force);
                break;

            //This is Impulse Mode, which involves using the Rigidbody’s mass to apply an instant impulse force.
            case ModeSwitching.Impulse:
                //The function converts the text fields into floats and updates the force applied to the Rigidbody
                MakeCustomForce();

                //Use Impulse as the force on GameObject
                m_Rigidbody.AddForce(m_NewForce, ForceMode.Impulse);
                break;


            //This is VelocityChange which involves ignoring the mass of the GameObject and impacting it with a sudden speed change in a direction
            case ModeSwitching.VelocityChange:
                //Converts the text fields into floats and updates the force applied to the Rigidbody
                MakeCustomForce();

                //Make a Velocity change on the Rigidbody
                m_Rigidbody.AddForce(m_NewForce, ForceMode.VelocityChange);
                break;
        }
    }

    //The function outputs buttons, text fields, and other interactable UI elements to the Scene in Game view
    void OnGUI()
    {
        //Getting the inputs from each text field and storing them as strings
        m_ForceXString = GUI.TextField(new Rect(300, 10, 200, 20), m_ForceXString, 25);
        m_ForceYString = GUI.TextField(new Rect(300, 30, 200, 20), m_ForceYString, 25);

        //Press the button to reset the GameObject and Rigidbody
        if (GUI.Button(new Rect(100, 0, 150, 30), "Reset"))
        {
            //This switches to the start/reset case
            m_ModeSwitching = ModeSwitching.Start;
        }

        //When you press the Acceleration button, switch to Acceleration mode
        if (GUI.Button(new Rect(100, 30, 150, 30), "Apply Acceleration"))
        {
            //Switch to Acceleration (apply acceleration force to GameObject)
            m_ModeSwitching = ModeSwitching.Acceleration;
        }

        //If you press the Impulse button
        if (GUI.Button(new Rect(100, 60, 150, 30), "Apply Impulse"))
        {
            //Switch to impulse (apply impulse forces to GameObject)
            m_ModeSwitching = ModeSwitching.Impulse;
        }

        //If you press the Force Button, switch to Force state
        if (GUI.Button(new Rect(100, 90, 150, 30), "Apply Force"))
        {
            //Switch to Force (apply force to GameObject)
            m_ModeSwitching = ModeSwitching.Force;
        }

        //Press the button to switch to VelocityChange state
        if (GUI.Button(new Rect(100, 120, 150, 30), "Apply Velocity Change"))
        {
            //Switch to velocity changing
            m_ModeSwitching = ModeSwitching.VelocityChange;
        }
    }

    //Changing strings to floats for the forces
    float ConvertToFloat(string Name)
    {
        float.TryParse(Name, out m_Result);
        return m_Result;
    }

    //Set the converted float from the text fields as the forces to apply to the Rigidbody
    void MakeCustomForce()
    {
        //This converts the strings to floats
        m_ForceX = ConvertToFloat(m_ForceXString);
        m_ForceY = ConvertToFloat(m_ForceYString);
    }
}