US-12619141-B2 - Image projection method for virtual tour

US12619141B2US 12619141 B2US12619141 B2US 12619141B2US-12619141-B2

Abstract

An image projection method for a virtual tour system is disclosed. The virtual tour system receives a panorama image derived from a panorama camera and comprises a local device. The local device comprises a display unit. The method comprises steps of: obtaining a distance factor according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and, forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint.

Inventors

Chung-Yen Lu

Assignees

CUPOLA360 INC.

Dates

Publication Date: 20260505
Application Date: 20230404

Claims (17)

1 . An image projection method for a virtual tour system receiving a panoramic image derived from a panorama camera and comprising a local device, the local device comprising a display unit, the method comprising steps of: obtaining a distance factor in a range of 0 to 1 in unit sphere space according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint, wherein the step of obtaining the distance factor comprises: converting a distance d between the panorama camera and the viewer in real word space into the distance factor, wherein the viewpoint is equivalent to the viewer, and wherein the step of converting comprises calculating the distance factor α by an equation: α=ρ×(1−e −d ), where 0<ρ<1.
2 . An image projection method for a virtual tour system receiving a panoramic image derived from a panorama camera and comprising a local device, the local device comprising a display unit, the method comprising steps of: obtaining a distance factor in a range of 0 to 1 in unit sphere space according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint, wherein the step of obtaining the distance factor comprises converting a distance d between the panorama camera and the viewer in real word space into the distance factor, wherein the viewpoint is equivalent to the viewer, and wherein the step of converting comprises: calculating the distance factor α by an equation: α=d/Rad, where Rad denotes an average distance from the panorama camera to multiple walls of a room in real world space.
3 . An image projection method for a virtual tour system receiving a panoramic image derived from a panorama camera and comprising a local device, the local device comprising a display unit, the method comprising steps of: obtaining a distance factor in a range of 0 to 1 in unit sphere space according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint, wherein the step of obtaining the distance factor comprises converting a distance d between the panorama camera and the viewer in real word space into the distance factor, and wherein the viewpoint is equivalent to the viewer, wherein the step of converting comprises: calculating a distance D between the panorama camera O and a point K on a wall of a room in real world space; and calculating the distance factor α by an equation: α=d/D, wherein vectors {right arrow over (OE)} and {right arrow over (OK)} have the same direction, and E denotes coordinates of the viewer in real world space.
4 . The image projection method according to claim 3 , wherein the step of obtaining the mapping coordinates comprises: calculating the mapping coordinates according to the distance factor, the distance d and the coordinates of the viewer in real world space.
5 . An image projection method for a virtual tour system receiving a panoramic image derived from a panorama camera and comprising a local device, the local device comprising a display unit, the method comprising steps of: obtaining a distance factor in a range of 0 to 1 in unit sphere space according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint, wherein the step of obtaining the distance factor comprises: determining a vertical component and a horizontal component according to a view direction vector and a vector from the panorama camera to the viewer in real world space; wherein the vertical component and the horizontal component are orthogonal and intersect at the viewpoint; and wherein the view direction vector is orthogonal to the view image.
6 . The image projection method according to claim 5 , wherein the step of obtaining the distance factor further comprises: determining the distance factor according to the horizontal component.
7 . The image projection method according to claim 6 , wherein the step of determining the distance factor comprises: calculating the distance factor α according to the horizontal component h by an equation: α=ρ×(1−e −h ), where 0<ρ<1.
8 . The image projection method according to claim 6 , wherein the step of determining the distance factor comprises: calculating the distance factor α according to the horizontal component h and an average distance Rad from the panorama camera to multiple walls of a room in real world space by an equation: α=h/Rad.
9 . The image projection method according to claim 5 , wherein the step of obtaining the distance factor further comprises: determining a FOV factor according to the vertical component.
10 . The image projection method according to claim 9 , wherein the step of determining the FOV factor comprises: when the vertical component ν is greater than zero, calculating the FOV factor β by an equation: β=(1 1 +1 2 ×e −|ν| ); when the vertical component ν is less than or equal to zero, calculating the FOV factor β by an equation: β=(1 3 −1 4 ×e −|ν| ); wherein 1 1 +1 2 =1 and 1 3 −1 4 =1.
11 . The image projection method according to claim 9 , wherein the step of determining the FOV factor comprises: when the vertical component ν is greater than zero, calculating the FOV factor β by an equation: β=(1−|ν|/Rad); when the vertical component ν is less than or equal to zero, calculating the FOV factor β by an equation: β=(1+|ν|/Rad); wherein Rad denotes an average distance from the panorama camera to multiple walls of a room in real world space.
12 . The image projection method according to claim 9 , wherein the step of determining the FOV factor comprises: calculating the FOV factor β by an equation: β=ν/(ν+D); wherein D denotes a distance between the viewer E and a point K on a wall of a room in real world space; and wherein {right arrow over (EK)} and the view direction vector have the same direction.
13 . The image projection method according to claim 5 , wherein the step of determining the vertical component and the horizontal component comprises: calculating the vertical component according to a dot product of the view direction vector and the vector from the panorama camera to the viewer in real world space; and calculating the horizontal component according to a distance between the panorama camera and the viewpoint in real world space.
14 . The image projection method according to claim 5 , wherein the step of obtaining the mapping coordinates comprises: determining the mapping coordinates according to the coordinates of the viewpoint in real world space, the distance factor and the horizontal component.
15 . The image projection method according to claim 9 , further comprising: modifying a default FOV according to the FOV factor to obtain a current FOV.
16 . An image projection method for a virtual tour system receiving a panoramic image derived from a panorama camera and comprising a local device, the local device comprising a display unit, the method comprising steps of: obtaining a distance factor in a range of 0 to 1 in unit sphere space according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint, wherein the step of forming comprises: determining color values of multiple selected pixels in the view image according to the mapping coordinates of the viewpoint, a field of view (FOV), a first set of three coordinate axis unit vectors and a second set of three coordinate axis unit vectors; wherein the first and the second sets of three coordinate axis unit vectors respectively the orientations of the view image and the panorama camera.
17 . The image projection method according to claim 16 , wherein the step of determining the color values comprises: for each selected pixel in the view image, calculating a point normalized vector according to the first set of three coordinate axis unit vectors, coordinates of the selected pixel in the view image and the FOV; calculating coordinates of a projection point on a unit sphere according to the mapping coordinates of the viewpoint and the point normalized vector; and determining the color values of the selected pixel by texture sampling the panoramic image according to the coordinates of the projection point and the second set of three coordinate axis unit vectors; wherein at least one of the FOV, the first set of three coordinate axis unit vectors and the coordinates of the viewer in real world space is updated according to input data from an input unit of the local device.

Description

BACKGROUND OF THE INVENTION Field of the Invention The invention relates to virtual tour, and more particularly, to image projection method for virtual tour. Description of the Related Art A virtual tour is a simulation of an existing position, usually composed of a sequence of videos, still images or 360-degree images. It may also use other multimedia elements such as sound effects, music, narration, text and floor map. It is designed to provide a realistic representation of a position that can be explored remotely from a computer, tablet or mobile device, without the need for physical travel. It is a powerful tool for marketing and promoting businesses, products, and services, and can also serve as an educational resource for students and researchers. FIG. 1 is an exemplary diagram showing a viewer roams an exhibition room with three partitions and four panorama cameras. Conventionally, virtual tours are created by two ways: three-dimensional (3D) modeling and panoramic images. (1) 3D modeling: involve a capture of a real-world position and the conversion of the capture into a 3D model so that each pixel in panoramic images has a corresponding depth value. As positions and view directions of a user/viewer 12 may change at will, view images for the viewer change accordingly. However, the downside of reconstructing the 3D modeling is high cost and difficult to maintain. (2) Panoramic images: all view images for a viewer 12 are formed based on a “fixed” point, i.e., the fixed position of a panorama camera in an independent space, such as the fixed position of a panorama camera 11-1 in an independent partition-1 in FIG. 1. Panoramic roaming (i.e., virtual tours are created by panoramic images) is widely used in digital exhibitions and street view maps because of its characteristics of low hardware requirements, good compatibility and strong sense of reality. Accordingly, what is needed is a new image projection method for a virtual tour system to form view images according to different positions, different field of views (FOVs) and different view directions of viewers, without reconstructing any 3D model/layout. SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the invention is to provide an image projection method for a virtual tour system, thereby to form view images according to different positions, different FOVs and different view directions (e.g., different view direction vectors) of viewers, without reconstructing any 3D model/layout. One embodiment of the invention provides an image projection method for a virtual tour system receiving a panorama image derived from a panorama camera and comprising a local device. The local device comprises a display unit. The method comprises steps of: obtaining a distance factor according to coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of a viewpoint related to the viewer in unit sphere space according to the distance factor and the coordinates of the viewer in real world space; and, forming a view image to be displayed by the display unit according to the mapping coordinates of the viewpoint. Another embodiment of the invention provides an image projection method for a virtual tour system receiving a panorama image derived from a panorama camera and comprising a local device. The local device comprises a display unit. The method comprises steps of: obtaining a distance factor, a field of view (FOV) factor and default coordinates of a viewpoint according to a view direction vector and coordinates of the panorama camera and a viewer in real world space; obtaining mapping coordinates of the viewpoint in unit sphere space according to the distance factor and the default coordinates of the viewpoint; modifying a default FOV according to the FOV factor to obtain a current FOV; and, forming a view image to be displayed by the display unit according to the mapping coordinates and the current FOV. Here, the view direction vector is orthogonal to the view image. Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: FIG. 1 is an exemplary diagram showing a viewer roams an exhibition room with three partitions and four panorama cameras. FIG. 2A is a block diagram of a virtual tour system with a real-time a