The invention relates to a method for creating an interactive virtual tour of a place, as well as a system for implementing such a method.

It applies in particular to virtual visits of places such as real-estate properties, especially apartments, houses or professional premises located in a building, but it can also apply to other types of places, such as boats or outside places.

To facilitate the work of real estate agents, there exist solutions for allowing the creation of interactive virtual tours of real-estate properties to be rent or bought by means of captured images of said real-estate properties, so as to allow a user to virtually visit said real-estate property through interactive browsing of said virtual tour.

Thus, real-estate agents can easily present real-estate properties to a great number of potential renters or buyers, in particular without planning physical displacements to said real-estate properties, which is particularly advantageous for customers that live far from said real-estate properties.

Some of the existing solutions provides for capturing images of the real-estate property through several 360° shooting sessions, and to create a virtual tour by photogrammetry, eventually completed with distance-measuring apparatuses, such as a laser or an infrared sensor.

A solution is known which provides for using photogrammetry only, without the use of additional measuring apparatuses, and provides to do so to perform several shooting sessions that are relatively very close from each other, notably with a relative distance of at most one or two meters between two adjacent shooting sessions. Another known solution provides for assembling a virtual tour by means of photogrammetry completed with infrared sensors and/or laser sensors.

These solutions require a very tight mesh of 360° panoramas, with relative distances between two adjacent panoramas not greater than 1 or 2 meters, for ensuring a reliable assembling of said panoramas. Thus, to ensure a correct visual continuity during the browsing into the final virtual tour, these solutions require a lot of different shooting sessions, and notably additional shooting sessions during passages between two rooms or behind elements that may hinder the visibility, such as wall corners or furniture.

However, these constraints are cumbersome and time-consuming for real-estate agents, which generally prefer to focus only on the points of interest of the properties to be visited. In particular, the transitions between two rooms separated by a long corridor may require uninteresting and time-wasting multiple shooting sessions within said corridor.

Moreover, there exist other solutions that provide a computing platform to allow a user to create such a virtual tour from 360° panoramas, but these solutions also require a manual assembly by the user of consecutive 360° panoramas to one another to perform such a creation, which takes a lot of time and sometimes requires computer knowledge from the user.

The invention aims to improve the prior art by proposing a solution for allowing to create an accurate interactive virtual tour of a place in a simple and reliable manner, and notably with a reduced number of shooting sessions.

For that purpose, and according to a first aspect, the invention relates to a method for creating an interactive virtual tour of a place for allowing a user to virtually visit said place through interactive browsing of said virtual tour, said method providing for:

- performing n consecutive shooting sessions, n being a natural number at least equal to 2, for capturing m angularly spaced images of said place by means of a mobile terminal, each of said shooting sessions being performed by rotation of said mobile terminal at a different location of said place, said mobile terminal comprising means for collecting its orientation when capturing the first image of each shooting sessions;

- generating, for each of the consecutive shooting sessions, a panorama projection by automatically assembling captured images of said shooting session;

wherein after the first shooting session at the first location, each further shooting session is performed by directing the mobile terminal so that the first image of said session is substantially centered on a previous location, the collected orientation at said direction being used to create a linking vector between the first images of respectively the further session and the previous session, said linking vectors being used to create interactive browsing means upon assembly of the panorama projections within an interactive virtual tour.

According to a second aspect, the invention relates to a system for implementing such a method for creating an interactive virtual tour of a place, said system comprising a mobile terminal which comprises:

- means for capturing the m angularly spaced images of said place during the n consecutive shooting sessions;

- rotation sensor means for collecting the orientation of said mobile terminal when capturing the first image of each shooting session;

- visor means for directing further shooting sessions on a previous location;

- an application comprising means for sending the captured images and the collected orientations to a platform of said system;

said platform comprising:

- means for assembling captured images of a shooting session into a panorama projection;

- means for creating the linking vectors from the collected orientations;

- means for assembling the panorama projections within an interactive virtual tour with interactive browsing means;

- means for displaying said interactive virtual tour, so as to allow a user to virtually visit said place through interactive browsing of said virtual tour. Other aspects and advantages of the invention will become apparent in the following description made with reference to the appended figures, wherein:

- figure 1 represents schematically the different steps of a method according to an embodiment of the invention;

- figure 2 represents schematically a plan in top view of an interactive virtual tour created by the method of figure 1.

In relation to those figures, we describe below a method for creating an interactive virtual tour of a place, as well as a system for implementing such a method, for allowing a user to virtually visit said place through interactive browsing of said virtual tour.

The place can be in particular a real-estate property, such as an apartment, a house or professional premises located in a building, the user being a potential buyer or renter for said real-estate property, or a real-estate agent who wants to present said real-estate property to a customer.

The place can also be of another type, such as for example a boat or any outside place.

The system comprises a mobile terminal T, such as for example a smartphone, that is equipped with integrated camera and sensors, as well as a platform which can be implemented into a server connected to a Local Area Network (LAN) or a Wide Area Network (WAN). Advantageously, the mobile terminal T comprises means for communicating with the platform through a wireless communication protocol, such as the Wi-Fi protocol or a Cellular Data protocol, especially of the third generation (3G), the fourth generation (4G) or the fifth generation (5G). The method provides for performing n consecutive shooting sessions Si-Sn, n being a natural number at least equal to 2, for capturing m angularly spaced images h-lm of the place by means of the mobile terminal T, which is equipped for that purpose with appropriate image capturing means, for example an integrated camera.

To implement the method, the mobile terminal T also comprises a dedicated application, which can be downloaded by the user of said mobile terminal from a dedicated application purchasing service, such as for example Google Play® or App Store®.

Each shooting session Si-Sn is performed by rotation of the mobile terminal T at a different location Li-L _n of the place, for example different rooms of a real-estate property, or different points within a same large room, such as for example a long corridor, a dining room or the main hall of a building.

During a shooting session Si-Sn, the mobile terminal T is immobile in relation to the corresponding location Li-L _n of the place, and only rotates around a vertical axis along an angular course of about 360°. To do so, the system comprises a tripod, such as the apparatus provided by the Nodalview® company, with a rotating head on which the mobile terminal T can be mounted, said head being adapted to rotate the mobile terminal T at 360° during a shooting session Si-Sn, either by manual or motorised rotation of said head around the vertical axis.

Advantageously, images l-i-lm are captured automatically by the mobile terminal T. To do so, the application can comprise means for interacting with the image capturing means of the mobile terminal T to automatically launch said image capturing means at the beginning of the rotation of said mobile terminal, so as to automatically capture images l-i-lm during said rotation. In particular, the application can be adapted to use information provided by rotation sensor means implemented on the mobile terminal T to launch the interaction means.

In particular, the rotating head of the tripod is adapted for allowing capture of the m images spaced from one another by a constant angular interval, preferably with a little value, so as to obtain an sufficient number of images h-lm for each shooting session S-i-Sn. For example, the constant angular interval may be of about 45°, which allows to obtain about 8 images per shooting session Si-Sn.

To that effect, when used with a motorised rotating head, the mobile terminal T can be adapted to command the rotation of said head, and to temporarily stop said rotation after each movement of said mobile terminal along the predefined angular interval. To do so, when the rotation sensor means detect the achievement of a movement along the angular interval, the mobile terminal T can send an appropriate signal to launch the image capturing means upon such a rotation stop.

The mobile terminal T also comprises means for collecting its orientation Oi-O _n at least when capturing the first image h of each shooting session Si-Sn, and preferably all along said shooting session, such collection means being for example rotation sensor means as presented hereinabove.

Moreover, the method provides that, after the first shooting session Si at the first location Li , each further shooting session Si is performed by directing the mobile terminal T so that the first image h of said session is substantially centered on a previous location Pj. To do so, the mobile terminal T comprises visor means adapted for such a direction.

For simplifying the achievement of the method, each further orientation Oi can be determined incrementally compared to the former orientation OM , i.e. the orientation OM of the mobile terminal T during the preceding shooting session SM . TO do so, the application can comprise means for registering consecutive orientations Oi-On of the mobile terminal T according to such an incrementation.

Moreover, the collected orientation Oi of the first shooting session Si can be set as a reference direction, notably for the further shooting sessions S2-S _n . To do so, the application can be adapted to do such a registration. In the same way, each further shooting session Si can be performed by directing the mobile terminal T so that the first image h of said session is substantially centered on the former location LM . In particular, the user of the mobile terminal T can place said mobile terminal at the further location Li so as to approximately orient said mobile terminal towards the former location LM before starting the further shooting session Si, notably by using the visors means described hereinabove.

Otherwise, in particular when the spatial arrangement of the room does not allow to perform a centering on the former location LM , the first image h of the further shooting session Si can be instead centered on a previous location Lj which is visible from the current location ϋ while being sufficiently close therefrom.

The method can provide for collecting the number j of the previous location Lj. To do so, the application comprises dedicated means which are adapted in particular for registering:

- by default, the number i-1 of the former location LM ; or

- a manual entering of said number j by the user of the mobile terminal T on a graphical user interface (GUI) of the application, notably in the case when a centering on said former location was impossible.

For a more intuitive registering of the sessions Si-Sn, the method can also provide for collecting a dedicated label corresponding to the name of the corresponding location Li-L _n , such as for example“living room”,“kitchen” or“entrance”. To do so, the application can comprise means for allowing the user to manually enter such a label after the achievement of a shooting session S-i-Sn.

Advantageously, the application can comprise means for processing in real-time visual parameters of the captured images h-lm to improve their quality, said parameters comprising for example the resolution, the brightness, the focus or the white balance. In particular, the application can comprise High-Dynamic- Range Imaging (IDRI) processing means, which are particularly adapted to function in parallel to pattern matching algorithms. The application further provides means for sending the captured images h-lm and the collected orientations O-i-On to the platform of the system. In particular, the sending means of the application can be adapted to automatically send the captured images l-i-lm and the collected orientations O-i-On, for example through a wireless communication according to the Wi-Fi protocol or a Cellular Data protocol, especially of the third generation (3G), the fourth generation (4G) or the fifth generation (5G). In relation to figure 1 , the method provides a step A for generating, for each of the consecutive shooting sessions Si-Sn, a panorama projection Pi-P _n by automatically assembling images l-i-lm captured during said shooting session. To do so, the platform comprises means for assembling images l-i-lm of a shooting session S-i-Sn into such a panorama projection Pi-P _n .

The panorama projections Pi -Pn are in particular equirectangular 360° panorama projections, which allows to benefit from an accurate representation of the corresponding location Li-L _n in the final interactive virtual tour. The method provides for processing each generated panorama projection Pi-P _n in order to align the centre of said panorama projection with the centre of the first image li captured during the corresponding shooting session Si -Sn. To do so, the platform comprises means that are adapted to achieve such an alignment process, for example by means of a Control Point Matching (CPM) algorithm, in particular the Speeded Up Robust Features (SURF) Control Point Detection algorithm.

The method also provides a step B, notably in parallel of step A, wherein, for each further shooting session Si, the collected orientation Oi at the direction of the mobile terminal T is used to create a linking vector Vi between the first images h of respectively said further session and the previous session Sj on which said further session was centered. To do so, the platform comprises means for creating such linking vectors Vi from the collected orientations Oi. The method then provides a step F for assembling the panorama projections P-i- Pn within an interactive virtual tour, the linking vectors Vi being used to create interactive browsing means IF upon said assembly. To do so, the platform comprises means for automatically performing such an assembly.

Thus, the method can replace automatically the panorama projections Pi-P _n in relation to one another and to generate automatically interactive browsing means IF for allowing transitions therebetween, notably without the use of additional and complex location data measurement technologies. Moreover, the automatic assembly of the interactive virtual tour allows to facilitate the work of real-estate agents and employees of real-estate agencies.

The method also provides a step C for creating a calibration matrix M from the linking vectors V2-V _n , said calibration matrix being used to create interactive browsing means IF between panorama projections Pi-P _n not directly linked by a vector V2-V _n . To do so, the platform comprises means for creating such a calibration matrix M, in particular before the final virtual tour assembly step F. The method also provides a step D for calibrating the panorama projections Pi- Pn with the matrix M created during step C, so that all of said panorama projections are linked two by two before their final assembly within the interactive virtual tour.

The interactive browsing means IF can be in the form of transition arrows with which the user can interact for switching from a panorama projection Pi-P _n to another one within the interactive virtual tour, and then to have a fluid overview of the place as if he was physically circulating between locations of interest thereof.

The interactive browsing means IF can be each defined by at least one of the following data: - vertical and horizontal coordinates of said interactive browsing means;

- information about the panorama projection Pi-P _n linked to said interactive browsing means; and

- vertical and horizontal coordinates of an entry view or an exit view of said panorama projection. In particular, in the case of browsing means IF from a panorama projection Pi to a previous panorama projection Pj, the entry view corresponds to the centre of the first image h of the panorama projection Pi.

The platform further comprises means for displaying the interactive virtual tour, so as to allow a user of said platform to virtually visit the place through interactive browsing of said interactive virtual tour.

In particular, the platform can comprise means for implementing a Graphical User Interface (GUI), for example a Web page for the real-estate agency, wherein a user can access to the interactive virtual tour of the real-estate property he is interested in to perform the virtual visit thereof, notably by interacting with the arrows IF for switching between the panorama projections Pi-P _n of each room of said real-estate property.

The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to assist the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.