WO2025201823A1

WO2025201823A1 - Real scene representation in extended reality applications

Info

Publication number: WO2025201823A1
Application number: PCT/EP2025/056032
Authority: WO
Inventors: Sylvain Lelievre; Patrice Hirtzlin; Etienne FAIVRE D'ARCIER; Pierrick Jouet; Loic FONTAINE; Stephane Onno
Original assignee: InterDigital CE Patent Holdings SAS
Current assignee: InterDigital CE Patent Holdings SAS
Priority date: 2024-03-26
Filing date: 2025-03-05
Publication date: 2025-10-02
Anticipated expiration: 2026-09-26
Also published as: EP4625117A1

Abstract

An extended reality system is proposed comprising a presentation engine and a scene understanding module configured to manage representation of the real part of the scene in a generic way. The presentation engine initializes the scene understanding module with the scene description that comprises data describing parameters to integrate the real scene and the virtual part of the extended reality scene. The scene understanding module manages a scene understanding representation thanks to data obtained from sensors or databases and warns the presentation engine of updates of the scene understanding representation. A generic API is defined for interactions between the two modules.

Description

REAL SCENE REPRESENTATION IN EXTENDED REALITY APPLICATIONS

1. Technical Field

The present principles generally relate to the domain of managing the real part of an extended reality (XR) scene. Scene descriptions are central for XR applications and the relationship with the real environment, essential. In particular, the present principles relate to methods and devices for managing a representation of a real scene, in real time, for generic renderer and/or XR application.

2. Background

The present section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present principles that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present principles. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

In the domain of extended Reality (XR) application, the knowledge of the real world may be required for different purposes. For example, the localization of the XR rendering device or for a seamless insertion of virtual content into the user’s real environment. Such knowledge about the real world can include the location of trackables items to correctly place virtual content according to the user(s), and to the 3D representation of the surrounding environment (point cloud, mesh, semantics) to ensure proper interactions between virtual and real content (occlusion, collision, physics). This knowledge of the real word (also called scene understanding) may be acquired in real time by an XR User equipment (UE), for example through an XR runtime module that collects user environment data through sensors and process them to build a real-world representation (e.g. a 3D scene graph). Some open standards specify an Application Programming Interfaces (API) for XR runtime module to provide high- performance access to XR functionalities. The UE can delegate the scene understanding processing to an edge server and sends a representation of it to this server, for example, pose information and images and/or video of the user environment. The real-world representation may be captured offline and/or stored into a world storage library from where scanned representations of real places are available for download. However, each solution is specific to an engine or to an XR application. There is a lack for a solution to manage representation of the real part of the scene in a generic way.

3. Summary

The following presents a simplified summary of the present principles to provide a basic understanding of some aspects of the present principles. This summary is not an extensive overview of the present principles. It is not intended to identify key or critical elements of the present principles. The following summary merely presents some aspects of the present principles in a simplified form as a prelude to the more detailed description provided below.

The present principles relate to a method for managing a representation of a real environment of a user of an extended reality scene. The method comprises obtaining a scene description. The scene description comprises first data describing a virtual part of the extended reality scene and second data describing parameters to integrate the real scene and the virtual part of the extended reality scene. A scene understanding representation is initialized with the second data. Then, changes of the real environment are observed and the scene understanding representation is updated according to these changes. The rendering of the extended reality scene based on the first data is adapted according to the updates of the scene understanding representation.

The present principles also relate to an extended reality scene presentation engine comprising a circuit configured to implement the method above. The present principles also relate to a scene understanding module comprising a circuit configured to implement the method above. Both circuits may belong a common device. 4. Brief Description of Drawings

The present disclosure will be better understood, and other specific features and advantages will emerge upon reading the following description, the description making reference to the annexed drawings wherein:

- Figure 1 illustrates a generic module to manage a representation of the real part of an XR scene according to the present principles;

- Figure 2 depicts an instantiation of the generic module of Figure 1 as a scene understanding module that maintains a representation of the user environment according to the present principles;

- Figure 3 shows an example architecture of a device which may be configured to implement methods according to embodiments of the present principles;

- Figure 4 depicts a first example of a sequence diagram illustrating the present principles;

- Figure 5 depicts a third example of a sequence diagram illustrating the present principles;

- Figure 6 depicts a second example of a sequence diagram illustrating the present principles.

5. Detailed description of embodiments

The present principles will be described more fully hereinafter with reference to the accompanying figures, in which examples of the present principles are shown. The present principles may, however, be embodied in many alternate forms and should not be construed as limited to the examples set forth herein. Accordingly, while the present principles are susceptible to various modifications and alternative forms, specific examples thereof are shown by way of examples in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the present principles to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present principles as defined by the claims.

The terminology used herein is for the purpose of describing particular examples only and is not intended to be limiting of the present principles. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising," "includes" and/or "including" when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Moreover, when an element is referred to as being "responsive" or "connected" to another element, it can be directly responsive or connected to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly responsive" or "directly connected" to other element, there are no intervening elements present. As used herein the term "and/or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as"/".

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the teachings of the present principles.

Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

Some examples are described with regard to block diagrams and operational flowcharts in which each block represents a circuit element, module, or portion of code which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in other implementations, the function(s) noted in the blocks may occur out of the order noted. For example, two blocks shown in succession may, in fact, be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending on the functionality involved.

Reference herein to “in accordance with an example” or “in an example” means that a particular feature, structure, or characteristic described in connection with the example can be included in at least one implementation of the present principles. The appearances of the phrase in accordance with an example” or “in an example” in various places in the specification are not necessarily all referring to the same example, nor are separate or alternative examples necessarily mutually exclusive of other examples. Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims. While not explicitly described, the present examples and variants may be employed in any combination or sub-combination.

In extended Reality (XR) application, the knowledge of the real world may be required for the localization of the XR device and for a seamless insertion of virtual content into the user’s real environment. Such knowledge about the real world can include the location of trackable items (like a QR code or a specific object) and anchors in order to correctly place virtual content according to the user(s). A 3D representation of the surrounding environment (point cloud, mesh, semantics) may also be necessary to ensure proper interactions between virtual and real content (occlusion, collision, physics). This knowledge of the real word may be acquired in real time by an XR User equipment (UE), thanks to an XR runtime module that collects user environment data through sensors (e.g. cameras, microphones, 3D scanners, ...) and process them to build a real-world representation (e.g. a 3D scene graph). The UE can delegate the scene understanding processing to an edge server by sending pose information and images and/or video of the user environment to this server. The real-world representation may be captured offline and stored into a world storage library from where scanned representations of real places are available for download. A presentation engine and scene manager module (PE module) uses an XR runtime module (through an API like, for instance, OpenXR) or a world analysis module to seamlessly integrate a virtual scene into the real world. The scene understanding process is performed by the XR runtime and/or the World Analysis modules. The virtual scene may come from a scene description file (e.g. a glTF scene description file) and the PE maintains a scene representation (PE Scene) according to its own internal structure. The world knowledge may be captured and analyzed in real time (by the XR runtime and the world analysis modules) or from already captured real world representations, stored in a world storage module.

In some architectures, a world analysis module uses a world API to request world objects related to the UE location from a world asset data base. It also uses the XR Runtime API (e.g. an OpenXR API) to request sensor’s data (UE environment data like camera images, position data from IMU (Inertial Measurement Unit) . . . ). These data are used to build in realtime a new representation of the real scene or to update the world object obtained from the world asset data base. The Presentation Engine can request representation of real objects using the XR Runtime or the World Analysis API. It can request pose information (e.g. the position of the UE or the trackables in the user environment) or user actions information (user input, gesture notification... ) using the XR Runtime API (e.g. an OpenXR API). The PE uses this information to place the virtual objects at the correct location and to render the part of the virtual scene that is seen by the user. The API mentioned above may be proprietary or from open standards. For illustration purpose, open standards like OpenXR™ are cited as examples that provide functionalities related to scene understanding. For instance, extensions to the OpenXR API (e.g. XR MSFT scene understanding and XR FB scene capture ) propose methods to configure and start scan processes and to request the representation of real objects.

As an example, and for illustration purpose, The XR MSFT scene understanding OpenXR extension provides applications with a structured, high-level representation of the planes, meshes, and objects in the user’s environment, enabling the development of spatially aware applications. The application requests computation of a scene, receiving the list of scene components observed in the environment around the user. In such an application, first an XrSceneObserverMSFT handle is created to manage the system resource of the scene understanding compute. Then, the application starts the scene computing by calling xrComputeNewSceneMSFT with XrSceneBoundsMSFT to specify the scan range and a list of XrSceneComputeFeatureMSFT features. The completion of computation is checked by polling xrGetSceneComputeStateMSFT. Once computing is completed, an XrSceneMSFT handle is created to the result by calling xrCreateSceneMSFT. Properties of scene components are obtained by using xrGetSceneComponentsMSFT, and, scene components are located by using xrLocateSceneComponentsMSFT. An application can also pass parameters to specify how the scan of the user environment should be computed. In an embodiment, the application can pass one or more bounding volumes that are used to determine which scene components to include in the resulting scene: Scene components entirely outside these volumes should be culled. The space parameter provides a reference coordinate system in which the coordinates of the bounding volumes and the scanned objects will be expressed. The time parameter gives a time at which the bounds volume will be evaluated within space.

In this example extension, an application can request that the system begin capturing information about what is in the environment around the user. The XrSceneCaptureRequestlnfoFB structure is used by an application to instruct the system what to look for during a scene capture. If the request parameter is NULL, then the runtime must conduct a default scene capture. The request parameter is a string that the application can use to specify what type of scene capture has to be initiated by the runtime. The content of buffer pointed to by the request parameter is runtime-specific. Thanks to the XR Runtime module, an XR UE can request the scan of the real environment. APIs exist for a presentation engine module to configure and request representation of the user environment, but the configuration data used with this API is specific to an engine or to an XR application. There is a lack for a generic solution. A content creator may want to insert in the description of its 3D virtual scene, some indications on how the scan should be performed, what elements of the 3D scene is needed (walls, floor, horizontal or vertical plane), what quality is needed for the scan object (simplified mesh, bounding boxes, textures, etc... .), in which spatial extent the real world must be analyzed and/or when should be performed update of the scan (once, timed or event based... ), for example.

Figure 1 illustrates a generic module 10 to manage a representation of the real part of an XR scene according to the present principles. This module and associated API 11 handle an external scene graph 12 that is synchronized with the virtual scene managed by a presentation engine 13. According to the present principles, semantics is provided to include information related to scene understanding in a virtual scene description file and to describe the representation of a real scene. Generic API 11 exposes to presentation engine 13 a set of functions that comprises initializing and configuring the external scene manager module (that is creation of a session between the two modules, setting of parameters needed by the external module to handle its scene); starting or stopping the external module processing; notifying the external module that an update occurred in the scene managed by the presentation engine; and registering callbacks for the external module to request status from the PE module or to notify that updates occurred in the external scene.

Figure 2 depicts an instantiation 21 of generic module 10 of Figure 1 as a scene understanding module that maintains a representation 22 of the user environment according to the present principles. In this example embodiment, this module is the unique entry point for a presentation engine module 23 to get the knowledge of the real scene around the user and to integrate a virtual scene into this real scene. Scene understanding (SU) module 21 creates and maintains a representation 22 of the real environment (for example, scene graph of the real- world scene) around the user. It gets updates of this scene graph by scanning in real-time the user environment (using the XR Runtime API) or by retrieving pre-scanned data from a world storage module. Presentation engine (PE) 23 may control the configuration and the starting of scene graph 22 creation and update. A generic API is proposed herein that provides methods for the PE. The scan of the user environment is linked to anchors and/or trackables that allow a link between a virtual scene and a place in the real environment where to integrate the virtual scene or elements of the virtual scene. Those anchors and trackables may be described in a virtual scene description file (e.g. glTF MPEG anchor extension). The PE can request the detection and the tracking of the trackables to the XR Runtime module. The detection and the tracking of a trackable results to the definition of an XR space in which the poses of one or more anchors are expressed. Another XR space is defined for each anchor, where the pose of virtual elements can be expressed. Both PE and SU modules may have access to the list of existing XR spaces and use them to spatially synchronize their scene graph. The Id of a trackable XR space (xrSpaceld) is given as input to the API methods to handle a scan of real objects around each trackable. Each xrSpaceld gives a mapping between a trackable described in the XR scene and a set of elements of the world scene. Each object of the world scene, returned by the SU module, comprises a set of attributes including a referenceld to identify it in the world scene as a unique object and a xrSpaceld to identify the XR space in which it is located. It may also comprise visual attributes like pose, mesh, material and texture description, lighting attributes for an object representing a real light source, physical attributes to handle interaction with other real or virtual objects (occlusion, collision... ). Additional parameters may include semantics information to specify the nature of the object (e.g. “wall”, “table”, “chair”, “light”, “sound”, ... ).

The following table provides a possible API according to the present principles:

In the configure () method, the scanOccurence parameter is a value specifying when the scan of real objects must be updated after a first call to the start () function. In a variant, the scan process may start automatically after a call to the configure () method. An extra “autostart” parameters may be added to this method to explicitly specify this automatic starting mode, the scanOccurence parameter may have different values: ONCE: the scan is performed only once, for instance in case of a static real scene; N_FRAME: the scan is performed periodically, every N rendering frames, N depending on the dynamism of the real scene; AUTO: the scan occurrence is managed by the SU module. The SU module may perform a light pre-analysis to detect significant moves in the real world and start a new scan from the beginning. This preanalysis may be performed from raw images data, like RGB images from a camera or depth images from a depth sensor. Several of these possible values may be combined to address different scenarios (e.g. ONCE AND AUTO). An object semantics may be any label representing a type of object: “wall”, “floor”, “table”, “chair”, “light”, “sound”, “freespace” ... Compute options and scan volumes may be similar to the one specified in the Microsoft OpenXR scene understanding extension, for example.

According to the present principles, semantics are defined in a scene description file. This semantic specifies if and how the user real environment should be integrated into the scene.

Semantics already exist in scene description language, e.g. MPEG-SD MPEG anchor extension that specify an element of the real world where virtual elements should be positioned. The semantics proposed herein may be added as new parameters in MPEG anchor extension, or a new MPEG node real (or any other name) extension may be specified, beside the MPEG anchor extension. These extensions are related to the glTF format, but we may add these semantics in extensions of any other description format (USD, FBX... ). In the following tables, the value in the column Usage indicates if the parameter is optional (O) or mandatory (M) according to the present principles.

Possible values for a scanOptions item may be:

Semantics of a scanDetail object may be: Possible values for a primitiveType may be:

The scanOccurence parameter is a value specifying when the scan of real objects must be updated. It may have the same format as the one in the configure () method of the API. Semantics for a scanVolumes object may be defined as follows. 3D coordinates are expressed in the XR space related to trackable associated to the anchor.

According to the present principles, a scene description format is proposed for the scan of the real scene provided by the “scene understanding” module. This format is related to the real-world objects returned by the getSceneComponents () method and the UPDATE callbacks of the API. It may be the description of the full space around the user, or it can be an update, with only the differences from a previous provision. The format defined hereafter is an example based on the Khronos glTF language, extended with MPEG-SD extensions, but similar features can be adapated to other languages, for instance the one used for the internal representation of the scene (PE scene). The scan of one or more real objects may come as a scene graph, for example glTF scene graph. Each root node of this graph is associated/mapped with a virtual node of the glTF scene of the PE module that features an MPEG anchor extension, i.e. the one who shares the same XR space. The transform matrix of a “real” node should be expressed in the trackable XR space (xrSpaceld). A “real” node may have a mesh and a texture generated and provided by the SU module. Extra parameters may be added to a “real” node inside a new MPEG node real extension (or any other name).

Figure 4 depicts a first example of a sequence diagram illustrating the present principles. It shows the exchanges between the PE module and the SU module during a 3D scene processing, involving real world elements. In this example, the SU module automatically sends World Scene updates using the registered callback.

The PE starts an XR application and receives an initial scene description file (step 1), describing the virtual elements to integrate in the real world. During an initialization phase, the PE parses the scene description file and retrieves the information related to the scene understanding processing (step 2). If the scan of real-world elements is needed to process the scene it uses the SU API to initialize and configure the SU module (steps 3, 4 and 5). The SU module registers the PE callbacks (step 6) that will be used to send real-world updates to the PE. The PE starts the scene understanding processing (step 7), but if the autostart parameter is set to True in the configure () method. During the rendering loop (i.e. the processing phase where the PE, at a given rate, process the 3D scene and create visual/audio frame to be presented to the user). If the PE receives real scene updates from the SU module (step 8), it parses the update data following the format proposed according to the present principles, and extracts real objects representations. If no update is sent by the SU module, the PE uses real objects representations previously received. The PE composes a mixed scene, made of real and virtual objects, and renders new frames (step 9).

Figure 6 depicts a second example of a sequence diagram illustrating the present principles. In this second example, no UPDATE callback is registered but only a STATUS callback. The PE uses the returned value of this STATUS callback to wait for available scan and retrieve real objects representations using the getSceneComponents () method.

Figure 5 depicts a third example of a sequence diagram illustrating the present principles. In this third example, at some point after the configure and the start of the scan have been launched, the XR application decide to change the scan processing. In that case, the PE module may use the stop () method and may redo the configuration and the starting processes with other parameters.

Figure 3 shows an example architecture of a device 30 which may be configured to implement methods according to embodiments of the present principles. The device is linked with other devices via their bus 31 and/or via I/O interface 36.

Device 30 comprises following elements that are linked together by a data and address bus 31 :D

- a processor 32 (or CPU), which is, for example, a DSP (or Digital Signal Processor);

- a ROM (or Read Only Memory) 33;

- a RAM (or Random Access Memory) 34;

- a storage interface 35;

- an I/O interface 36 for reception of data to transmit, from an application; and

- a power supply (not represented in Figure 2), e.g. a battery. In accordance with an example, the power supply is external to the device. In each of mentioned memory, the word « register » used in the specification may correspond to area of small capacity (some bits) or to very large area (e.g. a whole program or large amount of received or decoded data). The ROM 33 comprises at least a program and parameters. The ROM 33 may store algorithms and instructions to perform techniques in accordance with present principles. When switched on, the CPU 32 uploads the program in the RAM and executes the corresponding instructions.

The RAM 34 comprises, in a register, the program executed by the CPU 32 and uploaded after switch-on of the device 30, input data in a register, intermediate data in different states of the method in a register, and other variables used for the execution of the method in a register.

The implementations described herein may be implemented in, for example, a method or a process, an apparatus, a computer program product, a data stream, or a signal. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method or a device), the implementation of features discussed may also be implemented in other forms (for example a program). An apparatus may be implemented in, for example, appropriate hardware, software, and firmware. The methods may be implemented in, for example, an apparatus such as, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, such as, for example, computers, cell phones, portable/personal digital assistants ("PDAs"), and other devices that facilitate communication of information between end-users.

Device 30 is linked, for example via bus 31 to a set of sensors 37 and to a set of rendering devices 38. Sensors 37 may be, for example, cameras, microphones, temperature sensors, Inertial Measurement Units, GPS, hygrometry sensors, IR or UV light sensors or wind sensors. Rendering devices 38 may be, for example, displays, speakers, vibrators, heat, fan, etc.

In accordance with examples, the device 30 is configured to implement a method according to the present principles of managing a representation of the real environment of a user of an XR application, and belongs to a set comprising:

- a mobile device;

- a communication device; - a game device;

- a tablet (or tablet computer);

- a laptop;

- a still picture camera;

- a video camera.

The implementations described herein may be implemented in, for example, a method or a process, an apparatus, a computer program product, a data stream, or a signal. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method or a device), the implementation of features discussed may also be implemented in other forms (for example a program). An apparatus may be implemented in, for example, appropriate hardware, software, and firmware. The methods may be implemented in, for example, an apparatus such as, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, such as, for example, Smartphones, tablets, computers, mobile phones, portable/personal digital assistants ("PDAs"), and other devices that facilitate communication of information between end-users.

Implementations of the various processes and features described herein may be embodied in a variety of different equipment or applications, particularly, for example, equipment or applications associated with data encoding, data decoding, view generation, texture processing, and other processing of images and related texture information and/or depth information. Examples of such equipment include an encoder, a decoder, a post-processor processing output from a decoder, a pre-processor providing input to an encoder, a video coder, a video decoder, a video codec, a web server, a set-top box, a laptop, a personal computer, a cell phone, a PDA, and other communication devices. As should be clear, the equipment may be mobile and even installed in a mobile vehicle.

Additionally, the methods may be implemented by instructions being performed by a processor, and such instructions (and/or data values produced by an implementation) may be stored on a processor-readable medium such as, for example, an integrated circuit, a software carrier or other storage device such as, for example, a hard disk, a compact diskette (“CD”), an optical disc (such as, for example, a DVD, often referred to as a digital versatile disc or a digital video disc), a random access memory (“RAM”), or a read-only memory (“ROM”). The instructions may form an application program tangibly embodied on a processor-readable medium. Instructions may be, for example, in hardware, firmware, software, or a combination. Instructions may be found in, for example, an operating system, a separate application, or a combination of the two. A processor may be characterized, therefore, as, for example, both a device configured to carry out a process and a device that includes a processor-readable medium (such as a storage device) having instructions for carrying out a process. Further, a processor-readable medium may store, in addition to or in lieu of instructions, data values produced by an implementation.

As will be evident to one of skill in the art, implementations may produce a variety of signals formatted to carry information that may be, for example, stored or transmitted. The information may include, for example, instructions for performing a method, or data produced by one of the described implementations. For example, a signal may be formatted to carry as data the rules for writing or reading the syntax of a described embodiment, or to carry as data the actual syntax-values written by a described embodiment. Such a signal may be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of spectrum) or as a baseband signal. The formatting may include, for example, encoding a data stream and modulating a carrier with the encoded data stream. The information that the signal carries may be, for example, analog or digital information. The signal may be transmitted over a variety of different wired or wireless links, as is known. The signal may be stored on a processor-readable medium.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. For example, elements of different implementations may be combined, supplemented, modified, or removed to produce other implementations. Additionally, one of ordinary skill will understand that other structures and processes may be substituted for those disclosed and the resulting implementations will perform at least substantially the same function(s), in at least substantially the same way(s), to achieve at least substantially the same result(s) as the implementations disclosed. Accordingly, these and other implementations are contemplated by this application.

Claims

1. A method for managing a scene understanding representation of a real environment of a user of an extended reality scene, the method comprising:

- obtaining a scene description, the scene description comprising first data describing a virtual part of the extended reality scene and second data describing parameters to integrate the real environment and the virtual part of the extended reality scene;

- initializing a scene understanding representation with the second data;

- detecting at least one change of the real environment and updating the scene understanding representation according to the at least one change; and

- adapting a rendering of the first data according to the updates of the scene understanding representation.

2. The method of claim 1, wherein updating the scene understanding representation according to the at least one change of the real environment is performed by a scene understanding module and adapting the rendering is performed by a presentation engine.

3. The method of claim 2, wherein callbacks are defined by the presentation engine when initializing the scene understanding representation and wherein the scene understanding module uses the callbacks when the scene understanding representation is updated.

4. The method of claim 2, wherein the scene understanding module sends status update messages to the presentation engine when the scene understanding representation is updated and wherein the presentation engine requests updates of the scene understanding representation according to the status update messages.

5. An extended reality scene presentation engine comprising a circuit configured for:

- obtaining a scene description, the scene description comprising first data describing a virtual part of an extended reality scene and second data describing parameters to integrate a real environment and the virtual part of the extended reality scene;

- sending the second data to a scene understanding module for initializing a scene understanding representation; and

- adapting a rendering of the first data according to at least one update of the scene understanding representation received from the scene understanding module.

6. The extended reality scene presentation engine of claim 5, wherein the circuit is configured to define callbacks when sending the second data and wherein the scene understanding module uses the callbacks when the scene understanding representation is updated.

7. The extended reality scene presentation engine of claim 5, wherein the scene understanding module sends status update messages to the presentation engine when the scene understanding representation is updated and wherein the circuit requests updates of the scene understanding representation according to the status update messages.

8. A scene understanding module comprising a circuit configured for:

- receiving data from an extended reality scene presentation engine for initializing a scene understanding representation of a real environment of a user of an extended reality scene;

- sending at least one update of the scene understanding representation to the extended reality scene presentation engine.

9. The scene understanding module of claim 8, wherein callbacks are defined when initializing the scene understanding representation and wherein the circuit is configured to use the callbacks to send updates of the scene understanding representation to the extended reality scene presentation engine.

10. The scene understanding module of claim 8, wherein the circuit is configured to send status update messages to the extended reality scene presentation engine and to send updates of the scene understanding representation when receiving a request from the extended reality scene presentation engine.

11. A device comprising an extended reality scene presentation engine according to one of claims 5 to 7 and a scene understanding module according to one of claims 8 to 10.