The low level API provided for Spatial Mapping offers very fine-grained control over a complicated system.
下面列出的常见使用模式可能很有用：
__空间映射__低级 API 最重要的成员是 SurfaceObserver。此成员可用于深入了解设备对现实世界的理解。
SurfaceObserver 描述世界中的体积，并报告添加、更新或删除了哪些__表面__。应用程序随后可以在有或没有物理碰撞数据的情况下异步请求网格数据。请求完成后，另一个回调会通知应用程序这些数据已就绪。
SurfaceObserver 提供以下基本功能：
1.根据__表面__更改（例如添加、删除和更新）按需发出回调。 1.提供一个接口来请求与已知__表面__相对应的网格数据。 1.当请求的网格数据已可供使用时发出回调。 1.提供定义 SurfaceObserver 的位置和体积的方式。
另一个重要的移动部分是 SurfaceData 对象。此对象包含构建和报告__表面__网格数据所需的所有信息。
填充的 SurfaceData 在 RequestMeshAsync 调用中传递给系统。当网格数据准备就绪时，在请求时提供的“数据就绪”回调中会返回匹配的 SurfaceData。因此，应用程序可以精确确定数据对应的__表面__，不存在任何歧义。
应该根据应用程序所需的信息填充 SurfaceData 游戏对象。这包括传入：
当使用配置有误的 SurfaceData 来调用 RequestMeshAsync 方法时，系统会抛出参数异常。请注意，即使 RequestMeshAsync 没有抛出参数异常，也无法保证创建和返回网格数据。
此示例演示了此 API 的基本用法。
using UnityEngine;
using UnityEngine.VR;
using UnityEngine.VR.WSA;
using UnityEngine.Rendering;
using UnityEngine.Assertions;
using System;
using System.Collections;
using System.Collections.Generic;
public enum BakedState {
NeverBaked = 0,
Baked = 1,
UpdatePostBake = 2
}
// Data that is kept to prioritize surface baking.
class SurfaceEntry {
public GameObject m_Surface; // the GameObject corresponding to this surface
public int m_Id; // ID for this surface
public DateTime m_UpdateTime; // update time as reported by the system
public BakedState m_BakedState;
public const float c_Extents = 5.0f;
}
public class SMSample : MonoBehaviour {
// This observer is the window into the spatial mapping world.
SurfaceObserver m_Observer;
// This dictionary contains the set of known spatial mapping surfaces.
// Surfaces are updated, added, and removed on a regular basis.
Dictionary<int, SurfaceEntry> m_Surfaces;
// This is the material with which the baked surfaces are drawn.
public Material m_drawMat;
// This flag is used to postpone requests if a bake is in progress. Baking mesh
// data can take multiple frames. This sample prioritizes baking request
// order based on surface data surfaces and will only issue a new request
// if there are no requests being processed.
bool m_WaitingForBake;
// This is the last time the SurfaceObserver was updated. It is updated no
// more than every two seconds because doing so is potentially time-consuming.
float m_lastUpdateTime;
void Start () {
m_Observer = new SurfaceObserver ();
m_Observer.SetVolumeAsAxisAlignedBox (new Vector3(0.0f, 0.0f, 0.0f),
new Vector3 (SurfaceEntry.c_Extents, SurfaceEntry.c_Extents, SurfaceEntry.c_Extents));
m_Surfaces = new Dictionary<int, SurfaceEntry> ();
m_WaitingForBake = false;
m_lastUpdateTime = 0.0f;
}
void Update () {
// Avoid calling Update on a SurfaceObserver too frequently.
if (m_lastUpdateTime + 2.0f < Time.realtimeSinceStartup) {
// This block makes the observation volume follow the camera.
Vector3 extents;
extents.x = SurfaceEntry.c_Extents;
extents.y = SurfaceEntry.c_Extents;
extents.z = SurfaceEntry.c_Extents;
m_Observer.SetVolumeAsAxisAlignedBox (Camera.main.transform.position, extents);
try {
m_Observer.Update (SurfaceChangedHandler);
} catch {
// Update can throw an exception if the specified callback was bad.
Debug.Log ("Observer update failed unexpectedly!");
}
m_lastUpdateTime = Time.realtimeSinceStartup;
}
if (!m_WaitingForBake) {
// Prioritize older adds over other adds over updates.
SurfaceEntry bestSurface = null;
foreach (KeyValuePair<int, SurfaceEntry> surface in m_Surfaces) {
if (surface.Value.m_BakedState != BakedState.Baked) {
if (bestSurface == null) {
bestSurface = surface.Value;
} else {
if (surface.Value.m_BakedState < bestSurface.m_BakedState) {
bestSurface = surface.Value;
} else if (surface.Value.m_UpdateTime < bestSurface.m_UpdateTime) {
bestSurface = surface.Value;
}
}
}
}
if (bestSurface != null) {
// Fill out and dispatch the request.
SurfaceData sd;
sd.id.handle = bestSurface.m_Id;
sd.outputMesh = bestSurface.m_Surface.GetComponent<MeshFilter> ();
sd.outputAnchor = bestSurface.m_Surface.GetComponent<WorldAnchor> ();
sd.outputCollider = bestSurface.m_Surface.GetComponent<MeshCollider> ();
sd.trianglesPerCubicMeter = 300.0f;
sd.bakeCollider = true;
try {
if (m_Observer.RequestMeshAsync(sd, SurfaceDataReadyHandler)) {
m_WaitingForBake = true;
} else {
// A return value of false when requesting meshes
// typically indicates that the specified surface
// ID specified was invalid.
Debug.Log(System.String.Format ("Bake request for {0} failed. Is {0} a valid Surface ID?", bestSurface.m_Id));
}
}
catch {
// Requests can fail if the data struct is not filled out
// properly.
Debug.Log (System.String.Format("Bake for id {0} failed unexpectedly!", bestSurface.m_Id));
}
}
}
}
// This handler receives surface changed events and is propagated by the
// Update method on SurfaceObserver.
void SurfaceChangedHandler (SurfaceId id, SurfaceChange changeType, Bounds bounds, DateTime updateTime) {
SurfaceEntry entry;
switch (changeType) {
case SurfaceChange.Added:
case SurfaceChange.Updated:
if (m_Surfaces.TryGetValue(id.handle, out entry)) {
// If this surface has already been baked, mark it as needing bake
// in addition to the update time so the "next surface to bake"
// logic will order it correctly.
if (entry.m_BakedState == BakedState.Baked) {
entry.m_BakedState = BakedState.UpdatePostBake;
entry.m_UpdateTime = updateTime;
}
} else {
// This is a brand new surface so create an entry for it.
entry = new SurfaceEntry ();
entry.m_BakedState = BakedState.NeverBaked;
entry.m_UpdateTime = updateTime;
entry.m_Id = id.handle;
entry.m_Surface = new GameObject (System.String.Format("Surface-{0}", id.handle));
entry.m_Surface.AddComponent<MeshFilter> ();
entry.m_Surface.AddComponent<MeshCollider> ();
MeshRenderer mr = entry.m_Surface.AddComponent<MeshRenderer> ();
mr.shadowCastingMode = ShadowCastingMode.Off;
mr.receiveShadows = false;
entry.m_Surface.AddComponent<WorldAnchor> ();
entry.m_Surface.GetComponent<MeshRenderer> ().sharedMaterial = m_drawMat;
m_Surfaces[id.handle] = entry;
}
break;
case SurfaceChange.Removed:
if (m_Surfaces.TryGetValue(id.handle, out entry)) {
m_Surfaces.Remove (id.handle);
Mesh mesh = entry.m_Surface.GetComponent<MeshFilter> ().mesh;
if (mesh) {
Destroy (mesh);
}
Destroy (entry.m_Surface);
}
break;
}
}
void SurfaceDataReadyHandler(SurfaceData sd, bool outputWritten, float elapsedBakeTimeSeconds) {
m_WaitingForBake = false;
SurfaceEntry entry;
if (m_Surfaces.TryGetValue(sd.id.handle, out entry)) {
// These two asserts are checking that the returned filter and WorldAnchor
// are the same ones that the data was requested with. That should always
// be true here unless code has been changed to replace or destroy them.
Assert.IsTrue (sd.outputMesh == entry.m_Surface.GetComponent<MeshFilter>());
Assert.IsTrue (sd.outputAnchor == entry.m_Surface.GetComponent<WorldAnchor>());
entry.m_BakedState = BakedState.Baked;
} else {
Debug.Log (System.String.Format("Paranoia: Couldn't find surface {0} after a bake!", sd.id.handle));
Assert.IsTrue (false);
}
}
}
请注意，调用 Update 方法可能是资源密集型操作，因此调用次数不尽超出应用程序的请求频度。对于大多数用例来说，每三秒调用一次 Update 应该就足够了。