ARCore – Session、Frame、Camera 和 Pose [英] ARCore – Session, Frame, Camera and Pose

问题描述

我正在研究 ARCore

代码示例:

private Session mSession;Config config = new Config(mSession);如果(！mSession.isSupported(配置)){showSnackbarMessage(这款手机不支持 AR", true);}mSession.configure(config);

还有 Session 的配置可以包含嵌套类:

• Config.AugmentedFaceMode(选择Augmented Faces子系统的行为)
• Config.CloudAnchorMode(Config中的云锚点模式)
• Config.FocusMode(选择camera focus子系统所需的行为)
• Config.LightEstimationMode(选择光照估计子系统的行为)
• Config.PlaneFindingMode(选择plane detection子系统的行为)
• Config.UpdateMode(选择update()的行为)

#关于姿势

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Pose 表示从一个坐标空间到另一个坐标空间的不可变刚性变换.正如所有 ARCore API 提供的那样，姿势总是描述从对象的局部坐标空间到世界坐标空间的转换.变换是使用围绕原点的四元数旋转和平移来定义的.

代码示例:

float[] position = { 0, 0, -2.2 };//{ x, y, z } 位置float[] 旋转 = { 0, 0, 0, 1 };//{ x, y, z, w } 四元数旋转会话会话 = arFragment.getArSceneView().getSession();锚点 myAnchor = session.createAnchor(new Pose(position, rotation));

#关于 ARCamera

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ARCamera 代表一个虚拟相机，它决定了观察场景的视角.如果相机是 ArSceneView 的一部分，则相机会自动跟踪来自 ARCore 的相机姿势.ARCamera 是一个长期存在的对象，每次调用 Session.update() 时都会更新相机的属性.Camera 类提供有关用于捕获图像的相机的信息以及每个 ArFrame 内的附加信息.

代码示例:

//与 ARCore 共享相机访问sharedSession = new Session(this, EnumSet.of(Session.Feature.SHARED_CAMERA))sharedCamera = sharedSession.getSharedCamera();cameraId = sharedSession.getCameraConfig().getCameraId();

#关于ArFrame

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当 ARCore 对环境的理解发生变化时，它会调整其世界模型以保持一致.发生这种情况时，ARCamera 和 ARAnchors 的数字位置(坐标)会发生显着变化，以保持它们所代表的物理位置的适当相对位置.这些变化意味着每个 ArFrame 应该被认为是在一个完全唯一的世界坐标空间.ARAnchors 和 ARCamera 的数字坐标不应在检索它们的渲染帧之外使用.

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每个ArFrame 都存储了以下有关 ARCore 状态的信息::

• RGB 图像本身
• 跟踪状态
• 相机相对于世界的姿势
• 估计的照明参数
• 有关对象更新的信息(如点云)

代码示例:

private void onUpdateFrame(FrameTime frameTime) {帧 frame = arFragment.getArSceneView().getArFrame();//.....................}

此外，您可以阅读这篇有用的帖子.

I'm studying the ARCore References, Develop, make the course from Coursera, and read, understood and learn from the Samples.

But I still missing some definition with some real use examples.

What is a session? Every time that I need a ARCore use I need a session? Session always has a camera connect so I can see and draw/renderer my 3D models in the screen? Can I do this without a Session?

Camera has a getPose and Frame has a GetPose, what are the diferences between they?

I thought about make this questions split but somehow I know that they are all connected. Sessions, CameraAr, Frame and Pose.

解决方案

#About ArSession

ArSession is the most crucial element in AR puzzle. Session manages AR system state and handles the session lifecycle. Session class is the main entry point to the ARCore API. This class allows the user to create a session, configure it, start or stop it and, most importantly, receive ArFrames that allow access to ARCamera image and device Pose.

In order to use ARCore you need an ArSession. ARCore doesn't render 3D models (Renderables). This job is for Sceneform framework.

Code's example:

private Session mSession;
Config config = new Config(mSession);

if (!mSession.isSupported(config)) {
    showSnackbarMessage("This phone doesn't support AR", true);
}
mSession.configure(config);

Also Session's configuration can include nested classes:

• Config.AugmentedFaceMode (Selects the behaviour of Augmented Faces subsystem)
• Config.CloudAnchorMode (The cloud anchor mode in Config)
• Config.FocusMode (Selects the desired behaviour of the camera focus subsystem)
• Config.LightEstimationMode (Select the behaviour of the lighting estimation subsystem)
• Config.PlaneFindingMode (Select the behaviour of the plane detection subsystem)
• Config.UpdateMode (Selects the behaviour of update())

#About Pose

Pose represents an immutable rigid transformation from one coordinate space to another. As provided from all ARCore APIs, Poses always describe the transformation from object's local coordinate space to the world coordinate space. The transformation is defined using a quaternion rotation about the origin followed by a translation.

Code's example:

float[] position = { 0, 0, -2.2 };          //  { x, y, z } position 
float[] rotation = { 0, 0, 0, 1 };          //  { x, y, z, w } quaternion rotation

Session session = arFragment.getArSceneView().getSession();
Anchor myAnchor = session.createAnchor(new Pose(position, rotation));

#About ARCamera

ARCamera represents a virtual camera, which determines the perspective through which the scene is viewed. If the camera is part of an ArSceneView, then the camera automatically tracks the Camera Pose from ARCore. ARCamera is a long-lived object and the properties of camera are updated every time Session.update() is called. Camera class provides information about the camera that is used to capture images and additional info inside each ArFrame.

Code's example:

// Shared camera access with ARCore

sharedSession = new Session(this, EnumSet.of(Session.Feature.SHARED_CAMERA))
sharedCamera = sharedSession.getSharedCamera();
cameraId = sharedSession.getCameraConfig().getCameraId();

#About ArFrame

When ARCore's understanding of the environment changes, it adjusts its model of the world to keep things consistent. When this happens, the numerical location (coordinates) of the ARCamera and ARAnchors can change significantly to maintain appropriate relative positions of the physical locations they represent.These changes mean that every ArFrame should be considered to be in a completely unique world coordinate space. The numerical coordinates of ARAnchors and the ARCamera should never be used outside the rendering frame during which they were retrieved.

Every ArFrame stores the following info about ARCore's state::

• RGB image itself
• Tracking status
• The pose of the camera relative to the world
• Estimated lighting parameters
• Information on updates to objects (like Point Clouds)

Code's example:

private void onUpdateFrame(FrameTime frameTime) {

    Frame frame = arFragment.getArSceneView().getArFrame();

    // .............
}

Additionally, you can read this useful post.

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