Method for controlling a graphic interface for displaying the launching of a projectile in a virtual environment

A method for controlling a graphic interface for displaying images of a digital representation of a three-dimensional object, called launcher, in a virtual environment, the launcher being configured to launch a projectile in a virtual environment, wherein the launcher comprises a structure made of a non-magnetic material with a launching arm that is assembled so as to be mobile and constrained in movement, a magnet being fixed to the launching arm, the method being implemented by a computation unit, comprising the following steps:

• providing a locating device for locating the launcher in a tracking zone, comprising:
• an array of magnetometers fixed to a support surface,
• wherein the computation unit is connected to the array of magnetometers and to the graphic interface, and
• wherein the tracking zone for tracking the launcher with respect to the array of magnetometers is predefined, and a real three-dimensional reference frame is associated with the tracking zone;
• in storing, in the computation unit:
• a digital file coding the virtual environment in a virtual three-dimensional reference frame, the virtual three-dimensional reference frame being associated with the real three-dimensional reference frame via a predefined mapping relationship;
• a digital model making it possible to associate, with a state vector Xa|r of the magnet representative of the position and of the orientation of the magnet in the real three-dimensional reference frame, a state vector Xb,v of the launching arm representative of the position and/or of the orientation of the launching arm in the virtual three-dimensional reference frame, and making it possible to obtain a digital representation of the launcher in the virtual three-dimensional reference frame;
• manipulating, by a user, the launching arm, wherein the launcher is situated in the tracking zone and disposed in contact with the support surface, the launching arm being able to be away from a rest position by the user, a return member then exerting a return force on the launching arm toward the rest position;
• measuring, by the array of magnetometers, a magnetic field generated by the magnet at different successive measurement instants tn;
• determining the state vector Xa|r of the magnet in the real three-dimensional reference frame, at the measurement instant tn, from the measurements of the magnetic field generated by the magnet;
• determining, at the measurement instant tn, the state vector Xb|v of the launching arm in the virtual three-dimensional reference frame, from the prestored digital model and from the predetermined state vector Xa|r, and the position Pp|v of the projectile from the prestored digital model and from the predetermined state vector Xb|v;
• identifying an arming phase of the launching arm as a function of an arming factor K1 defined from the state vector Xb|v at the measurement instant tn and at prior measurement instants, wherein the arming phase is identified when the arming factor K1 is greater than or equal to a predefined threshold value K1s;
• when the arming phase is identified, identifying a firing of the projectile as a function of a launching factor K2 defined from the state vector Xb|v at the measurement instant tn, wherein the firing of the projectile is identified when the launching factor K2 is greater than or equal to a predefined threshold value K2s;
• when the firing of the projectile is identified, determining the successive positions Pp|v of the projectile in the virtual three-dimensional reference frame at subsequent measurement instants;
• constructing a two-dimensional image, representing, in the virtual three-dimensional reference frame, the virtual environment, the digital representation of the launcher, and the projectile, from the predetermined state vector Xb|v of the launching arm and from the predetermined position Pp|v of the projectile, then controlling the graphic interface by the computation unit to display the constructed image.