使用鼠标在3D空间中向各个方向移动对象

Question

I have this tracking project that I have worked on for a long time. Basically, the User moves a cube to trace the movements of a sphere which moves randomly. Currently, I am working with the User movements.

The issue is that the device that the user utilizes to move in all directions is a mouse in combination with the arrow keys. This is because the mouse handles two dimensions (xy), while the arrow keys handle two dimensions (xz). However, I would like to make it possible for me to just use the mouse.

As such, my professor suggested that I use the shift key to switch between xy and xz movements. However, I am confused as to how to go about this.

The code below represents what I have at this moment and what I have tried in regards to the shift key movements.

Could someone please help me solve this issue, or is there a better way to go about this?

Thank you!

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[RequireComponent(typeof(MeshCollider))]

public class UserController : MonoBehaviour {

public int speed = 20;

// Use this for initialization
void Start()
{

}

// Update is called once per frame
void Update()
{

    // get input data from keyboard or controller
    float moveHorizontal = Input.GetAxis("Horizontal");
    float moveVertical = Input.GetAxis("Vertical");

    // update player position based on input
    Vector3 position = transform.position;
    position.x += moveHorizontal * speed * Time.deltaTime;
    position.z += moveVertical * speed * Time.deltaTime;
    transform.position = position;
}

void OnMouseDrag()
{

    while(Input.GetMouseButton(0))
    {
        int shiftCalled = 0;
        //3D Drag, courtesy of Unity Forums
        if(Input.GetKey(KeyCode.LeftShift))
        {
            float distance_to_screen = Camera.main.WorldToScreenPoint(gameObject.transform.position).z;
            transform.position = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, distance_to_screen));
        }

        //Plane Drag, courtesy of Unity Forums
        if(Input.GetKey(KeyCode.RightShift))
        {
            float distance_to_screen = Camera.main.WorldToScreenPoint(gameObject.transform.position).z;
            Vector3 pos_move = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, distance_to_screen));
            transform.position = new Vector3(pos_move.x, transform.position.y, pos_move.z);
        }
    }





}
}

Answer 1

Here's what I would do -

Imagine a ray going from the position of the mouse on your screen towards a 2D plane that stretches on the X and Z angles. The intersection of said ray with the plane would be the X,Z coordinated that you wish your object to be dragged on. Now imagine the same ray intersecting with a different plane that stretches on the X and Y coordinates. This will generate the other type of movement you are looking for.

By holding the SHIFT button you will essentially be swapping these two planes, which should generate the result you are looking for.

You can generate both planes in code using -

xy_Plane = new Plane(Vector3.forward, m_DistanceFromCamera);
xz_Plane = new Plane(Vector3.up, m_DistanceFromCamera);

Generate the rays using -

 Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);

        //Initialise the enter variable
        float enter = 0.0f;

        if (xy_Plane.Raycast(ray, out enter))
            Vector3 hitPoint = ray.GetPoint(enter);

and check which plane should be used with -

if(Input.GetKey(KeyCode.Shift))

Now you only need to move your object based on the hitPoint you received.

Hope this helps.