KR20170142089A - Texture mapping calibration method for multi sided screen projection and apparatus thereof - Google Patents

Abstract

Embodiments of the present invention relate to a texture mapping method for three-sided image projection. According to an embodiment of the present invention, a method for correcting texture mapping for multi-sided image projection comprises the steps of: mapping a texture onto a first polyhedron; converting the first polyhedron onto which the texture is mapped into a second polyhedron composed of the number of polygons smaller than that of the first polyhedron; extracting a texture mapped onto a first region of the first polyhedron; and substituting a texture mapped onto a second region of the second polyhedron corresponding to the first region with the extracted texture. According to embodiments of the present invention, the image distortion occurring in texture mapping for multi-sided image projection can be reduced.

Description

TECHNICAL FIELD The present invention relates to a texture mapping correction method and apparatus for multi-view image projection,

Embodiments of the present invention are directed to a texture mapping scheme for multi-view image projection.

In computer graphics modeling, mapping is used to make the three-dimensional model more realistic. Among the methods of model mapping, texture mapping is often used. Also, a method of applying a bitmap image to a texture map or a mapping source in a texture mapping method is widely used. When you use the texture map to apply the surface of the model, you need to determine what part of the surface it will correspond to. This process sets the coordinate system corresponding to the texture map on the surface of the model. Since the bitmap image is a two-dimensional orthogonal plane, the corresponding surface must also be set on the model surface. The coordinate system set on the surface of the model is called a mapping coordinate system. If a mapping coordinate system is set on the model surface, it has a pixel value of the texture map of the corresponding coordinates.

Generally, a three-dimensional model is expressed using an orthogonal coordinate system of XYZ. Since the texture map must have a different coordinate system in relation to the mapping of the 3D model, it is expressed using the rectangular coordinate system of UVW. Conceptually, the UVW coordinate system corresponds to the XYZ coordinate system. Therefore, the texture map is expressed as an image with the horizontal direction as the U axis and the vertical direction as the V axis. Since the image has no depth information, the texture map is generally abbreviated as a UV map. Representative examples of mapping coordinates on the surface of the model include projection of the UVW coordinate system to the model in plane, cylinder, or sphere form. A planar projection method is to project a flattened image onto a model in the same direction. A cylindrical projection method is to project a cylindrical image of an image centered on a model. A spherical projection method is to project an image around a model in a spherical shape. Although many UV mapping methods are preferred for many texture mapping tasks, the UV rendering method has a very difficult problem. It occurs in the work of developing surfaces existing on three dimensions onto a two-dimensional plane. There is no problem if there is a simple development method, but it is impossible in the beginning to develop three-dimensional faces without any loss of information in two dimensions. As a result, we have to bear the loss of two pieces of information in order to forcefully spread the three-dimensional surface in two dimensions. First, in order to make the neighboring faces in three dimensions to be adjacent to each other in two dimensions, it is necessary to work to make faces. In the process of making faces, the area of each face decreases or increases. Second, in the case of a model with a hole like a pocket and a model with a hole closed without a hole, it can not be fully extended in 2D, so in the process of tearing and spreading the model, some faces are no longer neighbors with neighboring faces do.

Korean Patent Publication No. 2011-0060261 (Texture mapping system and method for three-dimensional objects)

Embodiments of the present invention provide a method for reducing distortion of an image that occurs in texture mapping for a multi-faceted image projection.

According to another aspect of the present invention, there is provided a method of correcting texture mappings for multi-view image projection, comprising: mapping a texture to a first polyhedron; Converting the texture-mapped first polyhedron into a second polyhedron having a smaller number of polygons than the first polyhedron; Extracting a texture mapped to a first area of the first polyhedron; And replacing a texture mapped to a second area of the second polyhedron corresponding to the first area with the extracted texture.

In one embodiment, the first region and the second region may be regions of the poles of the polyhedron.

In one embodiment, the extracting of the texture may include: selecting polygons having vertexes of the second polyhedron as vertexes as the second region; Selecting an area of the first polyhedron corresponding to the selected second area as the first area; And extracting a texture mapped to the selected first area.

In one embodiment, the first polyhedron may be in the form of a sphere.

A texture mapping correction apparatus for multi-sided image projection according to an exemplary embodiment of the present invention may include a processor and a memory. Wherein instructions for texture mapping are stored in the memory, wherein the instructions, when executed by the processor, cause the processor to map a texture to a first polyhedron and to map the first polyhedron to which the texture is mapped to the first polyhedron A polyhedron having a smaller number of polygons, extracting a texture mapped to a first area of the first polyhedron, and extracting a texture mapped to a second area of the second polyhedron corresponding to the first area, And substituting the extracted texture with the extracted texture.

According to embodiments of the present invention, it is possible to reduce distortion of an image occurring in texture mapping for a multi-image projection.

1 is an exemplary view for explaining a virtual reality experience space to which embodiments of the present invention are applied;
2 (a) to 2 (e) are views for explaining a texture mapping method using a 360-degree VR image,
3 (a) to 3 (e) are diagrams for explaining distortion of an image occurring at the time of conversion of a polyhedral structure,
FIGS. 4A through 4C are conceptual diagrams for explaining a texture mapping correction method according to an embodiment of the present invention; FIGS.
5 and 6 are diagrams for explaining a texture mapping correction method according to an embodiment of the present invention,
FIG. 7 is a flowchart illustrating a texture mapping correction method according to an embodiment of the present invention. FIG.
FIG. 8 is a block diagram for explaining a texture mapping correction apparatus according to an embodiment of the present invention; FIG.

In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is an exemplary diagram illustrating a virtual reality experience space to which embodiments of the present invention are applied.

The virtual reality experience space can be formed as a polyhedral image projection space and a polyhedral structure composed of a plurality of polygons. A user located in the virtual reality experience space can receive a VR service through a virtual reality (VR) image projected on a plurality of polygons. The material of each polygon may be opaque, transparent or translucent.

The virtual reality experience space may include a plurality of projectors 110. [ The plurality of projectors 100 may be arranged one by one corresponding to the polygons constituting the virtual reality experience space. The number of the projectors 110 may be equal to or less than the number of polygons constituting the polyhedral structure. For example, only the projector 100 corresponding to the remaining polygons excluding the polygons corresponding to the bottom surface among the polygons forming the virtual reality experience space may be disposed.

The plurality of projectors 110 can project the 360 degree VR image into the virtual reality experience space. The plurality of projectors 110 can receive the divided VR images in which the 360 degree VR images are divided and project the received divided VR images in the virtual reality experience space. For example, one of the projectors 110 may receive a divided VR image corresponding to a polygon constituting a virtual reality experience space, and project the received divided VR image to the corresponding polygon. A plurality of divided VR images are projected on a plurality of polygons constituting a virtual reality experience space, so that a seamless 360 degree VR image can be provided in the virtual reality experience space. The divided VR images can be received from the server managing the virtual reality experience space. According to the embodiment, each of the projectors 100 may be storing a divided VR image corresponding thereto. The plurality of projectors 110 may exist in the virtual reality experience space or may exist outside the virtual reality experience space.

On the other hand, in order to project a 360-degree VR image to a virtual reality experience space having a polyhedral structure, a two-dimensional texture is mapped to a polyhedron structure, a polyhedral structure mapped with a two-dimensional texture is converted into a polyhedron structure corresponding to a virtual reality experience space shall.

2 (a) to 2 (e) are diagrams for explaining a texture mapping method using a 360-degree VR image.

Texture mapping consists of three steps: mesh dismantling, texturing, and texture application.

For example, suppose that texture mapping is performed on a sphere having a polyhedral structure composed of a plurality of polygons, as shown in Fig. 2 (a).

If the mesh is disassembled into such a sphere, a UV map as shown in Fig. 2 (b) can be generated.

On the other hand, it is assumed that a texture as shown in FIG. 2 (c) is produced. When such a texture is applied to the UV map described with reference to FIG. 2 (b), a texture map applied to the UV map as shown in FIG. 2 (d) can be generated. When such a texture map is applied to a sphere as shown in FIG. 2A, a three-dimensional 360-degree VR image as shown in FIG. 2E can be generated.

In order to display the generated three-dimensional 360-degree VR image in the polyhedron structure as shown in FIG. 1, it is necessary to convert the spheres having the 360-degree VR image into a polyhedral structure corresponding to the virtual reality experience space.

In this conversion process, the coordinates may be damaged. As the converted polyhedron is composed of a small number of polygons, image distortion occurs more frequently. This distortion occurs especially at both poles.

Figs. 3 (a) to 3 (e) are diagrams for explaining distortion of an image that occurs during conversion of a polyhedral structure. Fig.

As shown in Fig. 3 (a), let us suppose that a texture is mapped to a sphere consisting of 40x40 polygons (1600 in total). Applying a polygon reduction algorithm to a texture-mapped sphere can produce a polyhedral structure with fewer polygons than the corresponding sphere. For example, a polyhedral structure composed of 20x20 polygons can be generated from a sphere composed of 40x40 polygons as shown in Fig. 3 (b). Thereafter, a polyhedral structure composed of 10 x 10 polygons can be generated from the polyhedral structure composed of 20 x 20 polygons as shown in Fig. 3 (c). Thereafter, a polyhedron structure consisting of 5x5 polygons can be generated from the polyhedron structure composed of 10x10 polygons as shown in Fig. 3 (d). Thereafter, the polyhedral structure of 5 x 5 polygons can be generated from the polyhedral structure of 4 x 4 polygons as shown in FIG. 3 (e).

3 (a) to 3 (e), it can be seen that the more the polyhedron is made of a small number of polygons, the more the image distortion, particularly the distortion of the image at the both poles, is generated.

4A to 4C are conceptual diagrams for explaining a texture mapping correction method according to an embodiment of the present invention.

As described above, when a texture-mapped polyhedron is converted into a polyhedron having fewer polygons than the polyhedron, many distortions occur at both the poles. Accordingly, by extracting the texture mapped to the polyhedral region 410 of the polyhedron as shown in FIG. 4 (a) and projecting it to the polyhedral region 420 of the polyhedron as shown in FIG. 4 (b) If the mapping is corrected, the distorted image can be removed. An example after the texture of the pole region 420 is corrected to the texture of the pole region 410 is shown in Fig. 4 (c). Referring to FIG. 4 (c), it can be seen that image distortion is reduced compared to FIG. 4 (b).

5 and 6 are diagrams for explaining a texture mapping correction method according to an embodiment of the present invention.

In the example described with reference to FIGS. 5 and 6, an example of correcting a texture mapped to a polygon 520 of 4 × 4 polygons using a texture mapped to a polygon 510 of 40 × 40 polygons will be described.

5 is a side view of the polyhedrons 510 and 520, and FIG. 6 is a view of the polyhedrons 510 and 520 in the direction of the pole.

First, after the polyhedron 510 is transformed into the polyhedron 520, the pole region 522, which is an area to be subjected to texture replacement of the polyhedron 520, can be selected. The pole region 522 may be selected by the user or by a set algorithm. For example, an area where polygons having apexes of apexes of the polyhedron 520 are located can be selected as the pole region 522.

Thereafter, a polynomial region 512 having UV coordinates corresponding to the pole region 522 of the polyhedron 520 may be selected in the polyhedron 510. When the pole region 512 of the polyhedron 510 is selected, the texture mapped to the pole region 512 can be extracted. Here, the text mapped to the pole region 512 may be a flattened image rendered without a perspective.

The texture extracted from the pole region 512 of the polyhedron 510 may then be mapped to the pole region 522 of the polyhedron 520. This mapping can be performed using the UV coordinate information of the pole region 512 and the pole region 522. [

7 is a flowchart illustrating a texture mapping correction method according to an embodiment of the present invention. Depending on the embodiment, at least one of the steps shown in Fig. 7 may be omitted.

In step 701, a first polyhedron is prepared. The first polyhedron may be formed of a predetermined number of polygons. The first polyhedron may be a group consisting of a predetermined number of polygons.

In step 703, a texture is mapped to the first polyhedron. For texture mapping, mesh disassembly of the first polyhedron, texture fabrication, and texture application may be performed. Depending on the embodiment, prefabricated textures may be used.

In step 705, a second polyhedron can be generated from the first polyhedron. The second polyhedron may be composed of a smaller number of polygons than the first polyhedron. The second polyhedron can be generated using a polygon reduction algorithm, as described with reference to Fig.

In step 707, the image of the second area of the second polyhedron may be replaced with the image of the first area of the first polyhedron. For example, as described with reference to FIGS. 5 and 6, the image of the pole region 522 of the polyhedron 520 may be replaced with the image of the pole region 512 of the polyhedron 510.

Embodiments of the invention may be embodied in a computer system, for example, a computer-readable recording medium. 8, the computer system 800 includes at least one of a processor 810, a memory 820, a storage 830, a user interface input 840, and a user interface output 850 Elements, which may communicate with each other via bus 860. [ In addition, the computer system 800 may also include a network interface 870 for connecting to a network. The processor 810 may be a CPU, a GPU, or a semiconductor device that executes processing instructions stored in the memory 820 and / or the storage 830. Memory 820 and storage 830 may include various types of volatile / non-volatile storage media. For example, the memory may include ROM 824 and RAM 825. [

Accordingly, embodiments of the invention may be embodied in a computer-implemented method or in a non-volatile computer storage medium having stored thereon computer-executable instructions. The instructions, when executed by a processor, may perform the method according to at least one embodiment of the present invention.

Claims (8)

Mapping a texture to a first polyhedron;
Converting the texture-mapped first polyhedron into a second polyhedron having a smaller number of polygons than the first polyhedron;
Extracting a texture mapped to a first area of the first polyhedron; And
Replacing a texture mapped to a second area of the second polyhedron corresponding to the first area with the extracted texture;
Wherein the texture mapping correction method comprises:
The method according to claim 1,
The first region and the second region are regions of the pole portion of the polyhedron
A Texture Mapping Correction Method for Multi - sided Image Projection.
The method of claim 1, wherein extracting the texture comprises:
Selecting polygons having apexes of the second polyhedron as the second regions;
Selecting an area of the first polyhedron corresponding to the selected second area as the first area; And
Extracting a texture mapped to the selected first area
Wherein the texture mapping correction method comprises:
The display device according to claim 1, wherein the first polyhedron comprises:
Sphere
A Texture Mapping Correction Method for Multi - sided Image Projection.
A texture mapping correction device comprising a processor and a memory,
Instructions for texture mapping are stored in the memory,
Wherein the instructions, when executed by the processor, cause the processor to:
Mapping a texture to the first polyhedron,
Converting the texture-mapped first polyhedron into a second polyhedron having a smaller number of polygons than the first polyhedron,
Extracting a texture mapped to a first area of the first polyhedron,
And replacing the texture mapped to the second area of the second polyhedron corresponding to the first area with the extracted texture
A texture mapping correction device for multi - sided image projection.
6. The method of claim 5,
The first region and the second region are regions of the pole portion of the polyhedron
A texture mapping correction device for multi - sided image projection.
6. The method of claim 5,
Selecting polygons having apexes of the second polyhedron as the apexes as the second regions,
Selecting an area of the first polyhedron corresponding to the selected second area as the first area,
And extracting a texture mapped to the selected first area
A texture mapping correction device for multi - sided image projection.
The method of claim 5, wherein the first polyhedron comprises:
Sphere
A texture mapping correction device for multi - sided image projection.

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