Unity第三人称相机构建(下)
上一集講完了相機的旋轉 ，現在我們要解決的問題是相機的剛性，要怎麼做呢？
相機剛性
Review the previously mentioned requirements:
滑鼠滾輪：控制相機遠近 相機不能穿透任何堅硬物體 當相機離開與堅固物體碰撞後，會慢慢回到原本的位置。 如果相機碰到剛體時，使用滑鼠滾輪操作相機拉近，相機需要立即回應，此後第6點不再發生；碰撞地面後不能進行縮放操作。 相機在旋轉時碰到地面，停止繞人物上下旋轉，改為繞自身上下旋轉，左右旋轉仍然是繞人物。
這幾點的意思是：相機在碰到堅硬的物體時，會被迫拉近跟人物的距離，那麼我們想要相機在離開的時候，可以慢慢地回到原來的距離；但是如果在自動拉近距離後，用滾輪再手動拉近，說明相機離開碰撞的物體，那麼這個拉近的距離就是相機的實際距離。下面我們來一點一點地解這些需求。
滾輪控制
滑鼠滾輪的控制相當簡單，只需知道如何獲取滾輪資訊，即Input.GetAxis("Mouse ScrollWheel")，並設定最大和最小的距離值就可以了：
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;
}
這裡的 playerTransform 指向角色。
無法穿透任何堅硬物體
這需要檢測相機跟剛體的接觸，有一個函數可以實現這個功能：
static bool Raycast(Ray ray, RaycastHit hitInfo, float distance = Mathf.Infinity, int layerMask = DefaultRaycastLayers);
(http://docs.unity3d.com/Documentation/ScriptReference/Physics.Raycast.html)我們可以透過以下方式實現碰撞檢測：
RaycastHit hitInfo;
if (Physics.Raycast(playerTransform.position, desiredPosition - playerTransform.position,
out hitInfo, (playerTransform.position - desiredPosition).magnitude, 1))
{
curDistance = hitInfo.distance;
}
targetPosition表示碰撞的位置，只要把相機設定到該位置即可。
離開剛體後，慢慢回到原來的距離上。
完成這功能的首要步驟是分別記錄相機應該處於的距離（desiredDistance）和目前的距離（curDistance），將滾輪操作的結果先存放在desiredDistance中，再根據碰撞計算物體的新距離； 當檢測到相機離開剛體或與更遠的剛體碰撞時，不可直接將碰撞位置賦予相機，而需透過移動速度來移動至新位置。首先取得新的距離：
float newDistance = desiredDistance;
RaycastHit hitInfo;
if (Physics.Raycast(playerTransform.position, desiredPosition - playerTransform.position,
out hitInfo, (playerTransform.position - desiredPosition).magnitude, 1))
{
newDistance = hitInfo.distance;
}
如何判斷相機正在往更遠的距離移動呢？你可以將 newDistances 與當前距離進行比較：
向更近的距離移動
if (newDistance < curDistance)
{
curDistance = newDistance;
}
向更遠的距離移動
else if(newDistance > curDistance)
{
}
在距離更遠的移動情況下做出判斷後，情況就變得很清晰了，直接增加速度來移動：
我們已經完成了相機的基本功能，接下來需要處理一些細節。碰到剛體後滾輪拉近，地面不縮放
這裡有兩個要求：
碰到剛體後只能拉近，不能拉遠 碰到地面後無法縮放
首先使用變數來保存相機的碰撞狀態：
在判斷滾輪縮放時加上條件判斷：
遇到地面時繞自身上下旋轉
這個功能實現起來有點麻煩，因為這時候我們之前假設相機一直對準人物的情況不成立了，現在要分成兩個向量：相機自身的朝向(desireForward)和人物到相機的方向(cameraToPlayer)，分別計算這兩個向量的值，前者決定相機的朝向，後者則決定相機的位置。為了方便起見，就把上一集中的旋轉函式拆分為X旋轉(RotateX)和Y旋轉(RotateY)，因此在計算cameraToPlayer的RotateY時，加入以下條件：
if ((!isHitGround) ||
(isHitGround && transform.forward.y <= cameraToPlayer.y && yAngle > 0))
{
cameraToPlayer = RotateY(cameraToPlayer, playerTransform.up,
transform.right, yAngle);
}
這個條件包含兩個部分：
- 未接觸地面 碰到地面，但是准备离开地面
然後使用 cameraToPlayer 計算相機的位置：
並且在有需要的時候(也就是碰到地面)計算相機的朝向：
if (!isHitGround)
{
transform.LookAt(playerTransform);
}
else
{
desireForward = RotateX(desireForward, playerTransform.up, xAngle);
desireForward = RotateY(desireForward, playerTransform.up, transform.right, yAngle);
transform.forward = desireForward;
}
我們已經實現了這款相機的功能。
完整代碼：
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;
}
}
Original: https://wiki.disenone.site/tc
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