Unity第三人称相机构建(下)
上一集讲完了相机的旋转，那么现在我们要解决的问题是相机的刚性，要怎么做呢？
相机刚性
回顾之前提的需求：
- 鼠标滚轮：控制相机远近
- 相机不能穿过任何刚性物体
- 相机在离开碰撞的刚性物体后，慢慢回到原来的距离上
- 如果相机在碰到刚体时，使用鼠标滚轮操作相机拉近，相机需要马上反应，此后第6点不再发生；碰撞地面后不能进行缩放操作
- 相机在旋转中碰到地面，停止围绕人物上下旋转，改为围绕自身上下旋转，左右旋转依然是围绕人物
这几点的意思是：相机在碰到刚性物体时，会被迫拉近跟人物的距离，那么我们想要相机在离开的时候，可以慢慢地回到原来的距离；但是如果在自动拉近距离后，用滚轮再手动拉近，说明相机离开碰撞的物体，那么这个拉近的距离就是相机的实际距离。下面我们来一点一点的解这些需求。
滚轮控制
鼠标滚轮控制很简单，只需要知道获取滚轮信息是Input.GetAxis("Mouse ScrollWheel")，并设定距离的最大值最小值就ok：
public float mouseWheelSensitivity = 2; // control zoom speed
public int mouseWheelZoomMin = 2; // min distance
public int mouseWheelZoomMax = 10; // max distance
float curDistance = 5F;
float zoom = Input.GetAxis("Mouse ScrollWheel");
if (zoom != 0F)
{
float distance = curDistance;
distance -= zoom * mouseWheelSensitivity;
distance = Math.Min(mouseWheelZoomMax, Math.Max(mouseWheelZoomMin, distance));
return distance;
}
这里playerTransform指向人物。
不能穿过任何刚性物体
这需要检测相机跟刚体的接触，有一个函数可以实现这个功能：
static bool Raycast(Ray ray, RaycastHit hitInfo, float distance = Mathf.Infinity, int layerMask = DefaultRaycastLayers);
具体用法参考Unity的Reference，我们可以这样实现碰撞的检测：
RaycastHit hitInfo;
if (Physics.Raycast(playerTransform.position, desiredPosition - playerTransform.position,
out hitInfo, (playerTransform.position - desiredPosition).magnitude, 1))
{
curDistance = hitInfo.distance;
}
targetPosition就是碰撞的位置，把相机的位置设到碰撞的位置就可以。
离开刚体后，慢慢回到原来的距离上
要完成这个功能，首先要分别记录下相机应该处于的距离(desiredDistance)和目前距离(curDistance)，把滚轮操作的结果用desiredDistance先存起来，再根据碰撞计算物体的新距离；
在检测到相机离开刚体，或者碰撞到更远的刚体时候，不能直接把碰撞的位置赋值给相机，需要用一个移动速度来向新的距离移动。先来获取新的距离：
float newDistance = desiredDistance;
RaycastHit hitInfo;
if (Physics.Raycast(playerTransform.position, desiredPosition - playerTransform.position,
out hitInfo, (playerTransform.position - desiredPosition).magnitude, 1))
{
newDistance = hitInfo.distance;
}
那么怎么判断相机正在向更远的距离移动呢？可以用newDistances和当前的距离进行比较：
// 向更近的距离移动
if (newDistance < curDistance)
{
curDistance = newDistance;
}
// 向更远的距离移动
else if(newDistance > curDistance)
{
}
那么判断到向更远距离移动后，就很直观了，直接加个速度来移动：
相机的大致行为我们已经完成了，还有一些细节需要处理。碰到刚体后滚轮拉近，地面不缩放
这里有两个要求：
- 碰到刚体后只能拉近，不能拉远
- 碰到地面后不能缩放
首先用变量来保存相机的碰撞状态：
在判断滚轮缩放的时候加上条件判断：
碰到地面绕自身上下旋转
这个功能实现起来有点麻烦，需要因为这时候我们之前假设相机一直对准人物不成立了，这时分成两个向量：相机自身的朝向(desireForward)和人物到相机的方向(cameraToPlayer)，分别计算这两个向量的值，前者就决定相机的朝向，后者就决定相机的位置。为了方便，把上一集的旋转函数拆成X旋转(RotateX)和Y旋转(RotateY)，那么在计算cameraToPlayer的RotateY时加上条件：
if ((!isHitGround) ||
(isHitGround && transform.forward.y <= cameraToPlayer.y && yAngle > 0))
{
cameraToPlayer = RotateY(cameraToPlayer, playerTransform.up,
transform.right, yAngle);
}
这个条件有两部分：
- 没有碰到地面
- 碰到地面，但是准备离开地面
然后用cameraToPlayer计算相机的位置：
并且在有需要的时候(也就是碰到地面)计算相机的朝向：
if (!isHitGround)
{
transform.LookAt(playerTransform);
}
else
{
desireForward = RotateX(desireForward, playerTransform.up, xAngle);
desireForward = RotateY(desireForward, playerTransform.up, transform.right, yAngle);
transform.forward = desireForward;
}
这样相机的行为我们都实现了。
完整代码：
using UnityEngine;
using System;
using System.Collections;
// use a forward vector and distance to describe the camera position
public class MyThirdPersonCamera : MonoBehaviour {
private Transform playerTransform; // reference to player
public float mouseWheelSensitivity = 3; // control zoom speed
public int mouseWheelZoomMin = 2; // min distance
public int mouseWheelZoomMax = 10; // max distance
public float rotateSpeed = 5F; // speed of rotate around player
public float autoZoomOutSpeed = 10F; // speed of auto zoom out, camera will auto zoom out
// to pre distance when stop colliding object
float curDistance = 5F; // distance to player
float desiredDistance = 5F; // distance should be
bool isHitGround = false; // hit ground flag
bool isHitObject = false; // hit object(except ground) flag
// Use this for initialization
void Awake ()
{
playerTransform = transform.parent;
}
void Start ()
{
transform.position = playerTransform.position - playerTransform.forward
* curDistance;
transform.LookAt(playerTransform);
}
// Update is called once per frame
void Update ()
{
Vector3 cameraToPlayer =
(playerTransform.position - transform.position).normalized;
Vector3 desireForward = transform.forward;
// get new distance of zoom
desiredDistance = ZoomIt(curDistance, desiredDistance);
float xAngle, yAngle;
bool isRightDown;
// get mouse LB, RB status
GetMouseButtonStatus(out xAngle, out yAngle, out isRightDown);
// rotate camera by x-axis movement
cameraToPlayer = RotateX(cameraToPlayer, playerTransform.up, xAngle);
// if RB on, change player orientation
if (isRightDown)
{
playerTransform.forward = Vector3.Normalize(new Vector3(cameraToPlayer.
x, 0, cameraToPlayer.z));
}
// rotate camera by y-axis, if camera is not on ground or camera is going to leave ground
if ((!isHitGround)
|| (isHitGround && transform.forward.y <= cameraToPlayer.y && yAngle > 0))
{
cameraToPlayer = RotateY(cameraToPlayer, playerTransform.up, transform.
right, yAngle);
}
// detect collision of camera to rigid body, get the distance camera should be
float newDistance = DealWithCollision(playerTransform.position,
-cameraToPlayer, desiredDistance,ref isHitGround, ref isHitObject);
// check the distance
if (newDistance <= curDistance)
{
curDistance = newDistance;
}
else
{
// now moving to farther position, use a speed to move it
curDistance = Math.Min(curDistance + Time.deltaTime * autoZoomOutSpeed,
newDistance);
}
// now calculate the position
transform.position = playerTransform.position - cameraToPlayer * curDistance;
// calculate the camera forward, if on ground, camera will rotate on self.Space
if (!isHitGround)
{
transform.LookAt(playerTransform);
}
else
{
desireForward = RotateX(desireForward, playerTransform.up, xAngle);
desireForward = RotateY(desireForward, playerTransform.up, transform.
right, yAngle);
transform.forward = desireForward;
}
}
// zoom in and zoom out
float ZoomIt(float curDistance, float desiredDistance)
{
float zoom = Input.GetAxis("Mouse ScrollWheel");
// zoom when hit rigid body and zoom in, or not on ground
if (zoom != 0F && (!isHitGround || (isHitObject && zoom > 0F)) )
{
float distance = curDistance;
distance -= zoom * mouseWheelSensitivity;
distance = Math.Min(mouseWheelZoomMax, Math.Max(mouseWheelZoomMin, distance));
return distance;
}
return desiredDistance;
}
// rotate oldPosition around a axis starting at axisPosition
Vector3 RotateAroundAxis(Vector3 point, float angle, Vector3 axis, Vector3 axisPosition)
{
Quaternion rotation = Quaternion.AngleAxis(angle, axis);
Vector3 offset = point - axisPosition;
return axisPosition + (rotation * offset);
}
void GetMouseButtonStatus(out float x, out float y, out bool isRightDown)
{
x = y = 0F;
isRightDown = false;
if (Input.GetMouseButton(0) ^ Input.GetMouseButton(1))
{
x = Input.GetAxis("Mouse X") * rotateSpeed;
y = -Input.GetAxis("Mouse Y") * rotateSpeed;
if (Input.GetMouseButton(1))
{
isRightDown = true;
}
}
}
// rotate vectorP2C(player to camera) around up while mouse x is on, return true if do rotate
Vector3 RotateX(Vector3 vectorP2C, Vector3 up, float angle)
{
Vector3 newVector = vectorP2C;
if (angle != 0F)
{
newVector = RotateAroundAxis(newVector, angle, up, Vector3.zero);
}
return newVector;
}
// rotate vectorP2C(player to camera) around right while mouse y is on, return true is do rotate
Vector3 RotateY(Vector3 vectorP2C, Vector3 up, Vector3 right, float angle)
{
Vector3 newVector = vectorP2C;
if (angle != 0F)
{
if ((Vector3.Dot(vectorP2C, up) >= -0.99F || angle < 0)
&& (Vector3.Dot(vectorP2C, up) <= 0.99F || angle > 0))
{
newVector = RotateAroundAxis(newVector, angle, right, Vector3.zero);
}
}
return newVector;
}
// return distance if no collision, else return distance to rigid body
float DealWithCollision(Vector3 origin, Vector3 direction, float distance,
ref bool ishitGround, ref bool ishitObject)
{
// collision detection
RaycastHit hitInfo;
float newDistance = distance;
if (Physics.Raycast(playerTransform.position, direction, out hitInfo, desiredDistance, 1))
{
if (hitInfo.collider is TerrainCollider)
{
ishitGround = true;
ishitObject = false;
}
else
{
ishitObject = true;
ishitGround = false;
}
newDistance = hitInfo.distance;
}
else
{
ishitGround = ishitObject = false;
}
return newDistance;
}
}
原文地址：https://wiki.disenone.site
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