Unity3d 框选

有时候，我们在游戏中会遇到需要框选对象的情况，比如红警。

在unity3d中可以用GL非常简单的实现。

1.先用GL画出线框，并求出Bounds

2.遍历对象，将对象的世界坐标转换到屏幕坐标，并测试该坐标是否在Bounds中。

using UnityEngine;

using System.Collections;

public class BoxSelector : MonoBehaviour {

Material _mat ;
bool _select = false;
Vector3 _p1;
Vector3 _p2;
GameObject _cubeObj;
Color _srcColor ;
Renderer _render ;

// Use this for initialization
void Start () {
if( !_mat )
{
_mat = new Material("Shader \"Lines/Colored Blended\" {" + "SubShader { Pass { " + "    Blend SrcAlpha OneMinusSrcAlpha " + " ZWrite Off Cull Off Fog { Mode Off } " + "    BindChannels {" + "      Bind \"vertex\", vertex Bind \"color\", color }" + "} } }");
}

_cubeObj = GameObject.Find("Cube");
_render = _cubeObj.GetComponent<Renderer>();
_srcColor = _render.material.color;

Bounds bounds = _cubeObj.GetComponent<BoxCollider>().bounds;
}

void OnDestroy()
{
Destroy(_mat);
}

// Update is called once per frame
void Update ()
{
if(Input.GetMouseButtonDown(0))
{
_select = true;
_p1 = Input.mousePosition;
}
if(Input.GetMouseButton(0))
{
_p2 = Input.mousePosition;
}
if(Input.GetMouseButtonUp(0))
{
_select = false;
Vector3 center = (_p1+_p2)*0.5f;
Vector3 size = new Vector3(Mathf.Abs(_p1.x-_p2.x),Mathf.Abs(_p1.y-_p2.y),0);
Bounds bounds = new Bounds(center,size);

BoxTest(bounds);
}

if(Input.GetMouseButtonDown(0))
{
Vector3 ray  = new Vector3(Input.mousePosition.x,Input.mousePosition.y,(_cubeObj.transform.position - Camera.main.transform.position).z);
Vector3 pos = Camera.main.ScreenToWorldPoint(ray);

RaycastHit hit;
if(Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition),out hit))
{
if(hit.collider.gameObject != _cubeObj)
{
_render.material.color = _srcColor;
}
}
else
{
_render.material.color = _srcColor;
}
}
}

void DrawBox(Vector3 p1,Vector3 p2)
{
_mat.SetPass(0);
GL.PushMatrix();
GL.LoadPixelMatrix();
GL.Begin(GL.LINES);
GL.Vertex(p1);
GL.Vertex3(p1.x,p2.y,0);
GL.Vertex3(p1.x,p2.y,0);
GL.Vertex(p2);
GL.Vertex(p2);
GL.Vertex3(p2.x,p1.y,0);
GL.Vertex3(p2.x,p1.y,0);
GL.Vertex(p1);
GL.End();
GL.PopMatrix();
}

void OnPostRender()
{
if(_select)
{
DrawBox(_p1,_p2);
}
}

void BoxTest(Bounds bounds)
{
if(_cubeObj)
{
Vector3 pos = Camera.main.WorldToScreenPoint(_cubeObj.transform.position);
pos.z = bounds.center.z;
if(bounds.Contains(pos))
{
_render.material.color = Color.blue;
}
}
}

void OnDrawGizmos()
{
if(_cubeObj != null)
{
Bounds bounds = _cubeObj.GetComponent<BoxCollider>().bounds;
Gizmos.color = new Color(1,0,0,0.5f);
Gizmos.DrawCube(_cubeObj.transform.position,bounds.size);
}
}

}