在官方的Demo2(drop_plank)中主要演示的是动态加载NavMesh。
首先还是一样,我们需要布置好场景,然后设置好NavMeshAgent。和之前不一样的是,这次不在场景中设置NavMeshSurface进行烘托(Bake),因为NavMeshSurface适用于场景不在改变的情况,提前烘托好寻路的网格。但是在demo2中,场景的都是一块块分开的。只有在游戏运行的时候,通过添加平板来连接起来。这个时候需要使用NavMeshBuilder。
首先,我们在场景中能行走的物体(方块和木板)添加NavMeshSourceTag脚本。其主要内容就是将场景中添加了NavMeshSourceTag的物体的MeshFilter都存放在一个静态数组当中。在Collect方法中,创建一个NavMeshBuildSource数组,对应存放的MeshFilter,供后面使用。
[DefaultExecutionOrder(-200)]
public class NavMeshSourceTag : MonoBehaviour {
// Global containers for all active mesh/terrain tags
public static List<MeshFilter> m_Meshes = new List<MeshFilter>();
public static List<Terrain> m_Terrains = new List<Terrain>();
void OnEnable() {
var m = GetComponent<MeshFilter>();
if(m != null) {
m_Meshes.Add(m);
}
var t = GetComponent<Terrain>();
if(t != null) {
m_Terrains.Add(t);
}
}
void OnDisable() {
var m = GetComponent<MeshFilter>();
if(m != null) {
m_Meshes.Remove(m);
}
var t = GetComponent<Terrain>();
if(t != null) {
m_Terrains.Remove(t);
}
}
// Collect all the navmesh build sources for enabled objects tagged by this component
public static void Collect(ref List<NavMeshBuildSource> sources) {
sources.Clear();
for(var i = 0; i < m_Meshes.Count; ++i) {
var mf = m_Meshes[i];
if(mf == null)
continue;
var m = mf.sharedMesh;
if(m == null)
continue;
var s = new NavMeshBuildSource();
s.shape = NavMeshBuildSourceShape.Mesh;
s.sourceObject = m;
s.transform = mf.transform.localToWorldMatrix;
s.area = 0;
sources.Add(s);
}
for(var i = 0; i < m_Terrains.Count; ++i) {
var t = m_Terrains[i];
if(t == null)
continue;
var s = new NavMeshBuildSource();
s.shape = NavMeshBuildSourceShape.Terrain;
s.sourceObject = t.terrainData;
// Terrain system only supports translation - so we pass translation only to back-end
s.transform = Matrix4x4.TRS(t.transform.position, Quaternion.identity, Vector3.one);
s.area = 0;
sources.Add(s);
}
}
}
然后Demo的场景中一个LocalNavMeshBuilder的物体有一个LocalNavMeshBuilder组件。在里面会逐帧执行NavMeshBuilder.UpdateNavMeshDataAsync(NavMeshData data, NavMeshBuildSettings buildSettings, List<NavMeshBuildSource> sources, Bounds localBounds);方法用于动态更新寻路网格。其中List<NavMeshBuildSource>就是上面NavMeshSourceTag组件中Collect获得的。
// Build and update a localized navmesh from the sources marked by NavMeshSourceTag
[DefaultExecutionOrder(-102)]
public class LocalNavMeshBuilder : MonoBehaviour {
// The center of the build
public Transform m_Tracked;
// The size of the build bounds
public Vector3 m_Size = new Vector3(80.0f, 20.0f, 80.0f);
NavMeshData m_NavMesh;
AsyncOperation m_Operation;
NavMeshDataInstance m_Instance;
List<NavMeshBuildSource> m_Sources = new List<NavMeshBuildSource>();
IEnumerator Start() {
while(true) {
UpdateNavMesh(true);
yield return m_Operation;
}
}
void OnEnable() {
// Construct and add navmesh
m_NavMesh = new NavMeshData();
//使NavMeshData可以被NavMeshAgent使用
m_Instance = NavMesh.AddNavMeshData(m_NavMesh);
if(m_Tracked == null)
m_Tracked = transform;
UpdateNavMesh(false);
}
void OnDisable() {
// Unload navmesh and clear handle
m_Instance.Remove();
}
void UpdateNavMesh(bool asyncUpdate = false) {
NavMeshSourceTag.Collect(ref m_Sources);
var defaultBuildSettings = NavMesh.GetSettingsByID(0);
var bounds = QuantizedBounds();
if(asyncUpdate)
m_Operation = NavMeshBuilder.UpdateNavMeshDataAsync(m_NavMesh, defaultBuildSettings, m_Sources, bounds);
else
NavMeshBuilder.UpdateNavMeshData(m_NavMesh, defaultBuildSettings, m_Sources, bounds);
}
static Vector3 Quantize(Vector3 v, Vector3 quant) {
float x = quant.x * Mathf.Floor(v.x / quant.x);
float y = quant.y * Mathf.Floor(v.y / quant.y);
float z = quant.z * Mathf.Floor(v.z / quant.z);
return new Vector3(x, y, z);
}
Bounds QuantizedBounds() {
// Quantize the bounds to update only when theres a 10% change in size
var center = m_Tracked ? m_Tracked.position : transform.position;
return new Bounds(Quantize(center, 0.1f * m_Size), m_Size);
}
void OnDrawGizmosSelected() {
if(m_NavMesh) {
Gizmos.color = Color.green;
Gizmos.DrawWireCube(m_NavMesh.sourceBounds.center, m_NavMesh.sourceBounds.size);
}
Gizmos.color = Color.yellow;
var bounds = QuantizedBounds();
Gizmos.DrawWireCube(bounds.center, bounds.size);
Gizmos.color = Color.green;
var center = m_Tracked ? m_Tracked.position : transform.position;
Gizmos.DrawWireCube(center, m_Size);
}
}
这样每帧都会进行更新寻路的网格,当添加一个木板的时候,也会将木板的mesh计算进去形成新的寻路网格。