Unity小地图的实现
游戏，特别是RPG类型，基本都需要添加小地图功能来辅助玩家。
实现小地图需解决的问题：
- 小地图（贴图）从哪里来？
- 如何把场景中单位的坐标转换到小地图上
- 小地图视角怎么跟玩家视角一致
思路：
- 让美术垂直90°方向以正交视角俯视整个场景，然后截取场景输出成图片，截取的大小让美术设置，一般不超过2048*2048
- 保存截图时的矩阵
- 通过第2点保存的矩阵，在游戏运行时把场景中单位的世界坐标转换到小地图下的局部坐标
实现：
- 根据设置（这里写死了800*600），设定截图窗口的大小，同时Camera视角校准为玩家视角，我这里是直接使用Scene窗口
if (GUILayout.Button("调整截图窗口大小"))
{
var windowSize = Vector2(800,600);
var lastSceneView = SceneView.lastActiveSceneView;
// 场景的Main Camera
var mainCamera = UnityEngine.Camera.main;
// SmoothFollow是镜头跟踪的组件，这里知道SmoothFollow里有个rotationAngle字段是记录玩家视角即可
XS.SmoothFollow smoothFollow = null;
if (mainCamera)
{
smoothFollow = mainCamera.GetComponent<XS.SmoothFollow>();
}
if (smoothFollow == null)
{
return;
}
lastSceneView.position = new Rect(Vector3.zero, windowSize);
Quaternion currentRotation = Quaternion.Euler(90, smoothFollow.rotationAngle, 0);
lastSceneView.LookAt(Vector3.zero, currentRotation, lastSceneView.size, true);
lastSceneView.isRotationLocked = true;
}
- 截图时，以Scene的大小为图片宽高，并预先算出此时的world2Screen矩阵和screen2World矩阵，用于后面的逻辑运算
if (GUILayout.Button("截取小地图"))
{
var lastSceneView = SceneView.lastActiveSceneView;
var sceneCamera = lastSceneView.camera;
if (!sceneCamera.orthographic)
{
return;
}
var width = sceneCamera.pixelWidth;
var height = sceneCamera.pixelHeight;
var cameraPos = sceneCamera.transform.position;
var camreaSize = sceneCamera.orthographicSize;
Matrix4x4 world2Screen = sceneCamera.projectionMatrix * sceneCamera.worldToCameraMatrix;
Matrix4x4 screen2World = world2Screen.inverse;
RenderTexture sceneCameraRT = RenderTexture.GetTemporary((int)width, (int)height, 32, RenderTextureFormat.ARGBFloat);
sceneCamera.targetTexture = sceneCameraRT;
sceneCamera.Render();
sceneCamera.targetTexture = null;
// targetData是用于保存数据组件，挂载在场景的一个空Object上
string sceneName = targetData.gameObject.scene.name;
var path = EditorUtility.SaveFilePanel("Save SmallMap", "", sceneName, "png");
if (!string.IsNullOrEmpty(path))
{
if (SaveRenderTextureToPNG(sceneCameraRT, path))
{
targetData.smallMapCameraCenter = cameraPos;
targetData.smallMapCameraSize = camreaSize;
targetData.smallMapWorldToScreenMatrix = world2Screen;
targetData.smallMapScreenToWorldMatrix = screen2World;
targetData.smallMapCutSize = new Vector2(width, height);
UnityEditor.EditorUtility.SetDirty(targetData);
UnityEditor.SceneManagement.EditorSceneManager.MarkSceneDirty(targetData.gameObject.scene);
}
else
{
Debug.LogError("Save RenderTexture to file error");
}
}
RenderTexture.ReleaseTemporary(sceneCameraRT);
}
- 根据第2点保存的两个矩阵和图片大小，通过以下接口(Lua实现)即可完成坐标转换，里面涉及的数学知识请自行查阅。
-- 世界坐标转图片的局部坐标
function manualWorldToScreenPoint(world2Screen, x, z, pixelWidth, pixelHeight)
local temp = world2Screen * UnityEngine.Vector4(x, 10, z, 1.0)
if temp.w == 0 then
return UnityEngine.Vector3.zero
else
temp.x = (temp.x/temp.w + 1)*0.5 * pixelWidth
temp.y = (temp.y/temp.w + 1)*0.5 * pixelHeight
return temp.x, temp.y
end
end
-- 图片的局部坐标转世界坐标
function manualScreenPointToWorld(screen2World, x, y, pixelWidth, pixelHeight)
local in_x = 2.0 * (x / pixelWidth) - 1.0
local in_y = 2.0 * (y / pixelHeight) - 1.0
local in_z = 10
local in_w = 1.0
local pos = screen2World * UnityEngine.Vector4(in_x,in_y,in_z,in_w)
if pos.w == 0 then
return UnityEngine.Vector3.zero
else
pos.w = 1.0 / pos.w
pos.x = pos.x*pos.w
pos.y = pos.y*pos.w
pos.z = pos.z*pos.w
return pos.x, pos.z
end
end
额外：
小地图一般需要添加小地图寻路功能，这里我使用的方案是给小地图添加PointerClick事件，根据点击的坐标点转换成世界坐标点，然后从在一点(当然是上移到场景上空)通过射线往下检测，得到与路面（路面需要设置特定Layer）的交点，这个交点就是目标点，接下来就是UnityEngine.AI.NavMeshAgent的事情了。
