JP2001229401A - Method for embedding electric watermark in three- dimensional shape model - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for embedding an invisible watermark in three- dimensional shape model data. SOLUTION: This method for embedding an electronic watermark in a three- dimensional shape model has a 1st step for selecting part of the three- dimensional shape data as a watermark embedded part, selecting a necessary number of vertexes from the vertexes constituting the watermark part, and composing three-dimensional shape data for a watermark of new vertexes obtained by duplicating the mentioned vertexes, a 2nd step for inverting the directions of the respective planes constituting the shape for the watermark to the opposite directions of the corresponding planes of the original three- dimensional shape data, a 3rd step for arranging the shape for the watermark at the embedded part of the original three-dimensional shape data and connecting the both, and a 4th step for removing overlapping vertexes of the shape for the watermark and the embedded part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a digital watermarking technique for embedding copyright display information and the like in three-dimensional shape model data. In recent years, digital data expressing three-dimensional shapes has been transmitted through the Internet and CD-ROM media.
The use of distribution and distribution technologies in the industry is increasing,
The present invention can be used in such a field.

[0002]

2. Description of the Related Art As in an electronic museum on the Internet, cases of distributing digital data of three-dimensional shapes in addition to characters, images, and voices are increasing. Such data can be easily copied in an unauthorized manner as in the case of an image or the like. Therefore, means for protecting ownership is desired.

At present, it is common practice to embed copyright information as a text comment in a data file of a three-dimensional shape model. However, information embedded in text is easily removed by a text editor or the like. You can do it. Also, when the data is read into the editing software for the three-dimensional shape and then saved in another file format, the copyright information embedded as a text comment is often removed. Under such circumstances, there has been no effective means for protecting the three-dimensional shape model from plagiarism such as unauthorized copying.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in consideration of such problems, and has as its object to embed an invisible digital watermark into three-dimensional shape model data. To provide a method. By embedding appropriate information in accordance with the purpose, it becomes possible to prove the creator of the data, check the data for secondary use without copying the data without the creator's permission, and the like.

[0005]

FIG. 1 is a flow chart showing a method of the present invention devised to solve the above-mentioned problems. That is, in the method of the present invention, a part of the three-dimensional shape data is selected as a watermark embedding part, a required number of vertices are selected from the vertices constituting the watermark embedding part, and a watermark is copied from a new vertex. A first step (S1) of forming three-dimensional shape data for use in the first step (S1), and a second step of inverting the direction of each surface forming the shape for watermark in a direction opposite to the direction of the corresponding surface of the original three-dimensional shape data Step (S2), a third step (S3) of arranging a watermark shape in the embedded portion of the original three-dimensional shape data and combining them so that they are the same node, This is a method of embedding a digital watermark in a three-dimensional shape model, which comprises a fourth step (S4) of removing overlapping vertices.

According to the method of the present invention, in the first step, three-dimensional shape data for watermarking is created from vertices having the same coordinate values as the vertices selected in the required number from the watermark-embedded part. At this time, in order to prevent the watermark from appearing when displayed in the wire frame model, the line segments constituting the created watermark shape data are configured so that nothing protrudes from the watermark embedding portion. In other words, in the created watermark shape data, the sides (line segments defined as graphic elements,
Or, a series of such line segments is not formed.

Computer graphics (CG)
In the rendering calculation, a process called hidden surface removal is performed. It is determined whether each face of the CG object is face up or face down, and the face facing down is made invisible. The orientation of the surface is determined by the sign of the inner product of the normal vector N of the surface and the line-of-sight vector V as shown in FIG. In other words, if the inner product is positive (the angle between N and V is acute), the inner product is negative (N
And the angle between V and V is obtuse). If there is no other face up before the face up, that face is displayed. In the method of the present invention, utilizing this principle, in the second step, the normal vector of each surface of the component of the watermark shape is set so as to have the normal vector opposite to the surface to which it is pasted. Define.

In the third step, the watermark embedded portion of the original three-dimensional shape and the embedded watermark shape are set to the same node, so that the three-dimensional shape model with the embedded watermark is read into the three-dimensional modeling tool. This is a process for preventing the presence of a watermark from being perceived on the scene graph even if it is rare.

In the fourth step, by removing vertices where the coordinate values of the watermark shape and the shape of the embedment part overlap, the embedded watermark data is given a resistance to data processing. This means that if the user of the three-dimensional model data can extract the watermark shape data by some method or by accident, if the user tries to remove the extracted watermark shape part, Since the watermark shape shares one or more vertices with the original three-dimensional shape data, a part of the original three-dimensional shape data is always damaged, so it is impossible to remove only the watermark shape. That is not possible.
As a result, some vertices are shared with the watermark-embedded portion of the original three-dimensional shape, and the respective surfaces constituting the watermark shape are assigned to the watermark-embedded portion from the same side (shared side). A watermarking shape is created that is defined such that there is always a reverse surface configured.

In another preferred embodiment of the present invention,
After the first to fourth steps, a method is possible in which a fifth step of setting the surface attribute of the watermark shape to be the same as that of the surface shape to be embedded is added. This procedure is shown in the flowchart of FIG. By adding the fifth step (S5), the watermark shape becomes more difficult to be recognized, which is more preferable.

A second invention is a watermark shape which shares some vertices with a watermark embedding portion which is a part of a three-dimensional shape, and each face constituting the watermark shape is the watermark. This is a computer-readable recording medium that records three-dimensional shape modeling data including a watermark shape defined so that an embedded surface has an opposite surface composed of the same side. Such a watermark shape can of course be created by the method of the first invention, but may be created by other methods.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the method of the present invention will be described with reference to specific examples.

(Original Three-Dimensional Shape) A three-dimensional shape model in which a digital watermark is to be embedded and illegal copying is to be suppressed is formed as shown in FIG. Here, the watermark is applied to the surface with the previous mesh, that is, the vertices (1,1,1) (-1,1,1) (-1, -1,1)
FIG. 3 shows an example of the configuration of the polygon of the surface 100 which is embedded in the surface 100 defined by (1, -1,1). In FIG. 3, it is composed of many small quadrangular polygons. The figure shown in FIG. 3 corresponds to the embedded portion in this case.

(Creation of Watermark Shape) A procedure for creating a watermark shape to be embedded as a digital watermark will be described below. First, information to be embedded in a three-dimensional shape is prepared as a digital watermark.
The information to be embedded may be characters indicating the creator and the copyright holder of the three-dimensional shape data as shown in FIG. 4, or a logo or graphic. Such information is replaced with an appropriate polygonal figure. At this time, as shown in FIG. 5, the information to be embedded is replaced with a polygon figure having vertices having the same coordinate values as the vertices of the polygon in FIG. This operation can be performed interactively on a three-dimensional shape modeling system usually used by a CG production operator, for example. FIG. 6 shows the information to be embedded in this manner, in which all vertices and sides are the faces 100.
The figure shows a case where the polygon is replaced with a polygonal figure that matches the mesh of FIG. The polygonal figure of FIG.
00.

(Inversion of Normal Vector) In order to paste the created watermark shape 200 on the back surface of the original three-dimensional shape data, the normal vector of the polygonal surface constituting the watermark shape 200 is inverted. . This inversion is, specifically,
Either re-define the surface by reversing the arrangement of the vertex sequence defining the surface of the polygon, or rewrite the attribute of the surface as a normal vector. Which to do is adopted 3
In any case, the inversion of the normal vector can be described as a fixed algorithm, and can be automatically processed by a program, although it depends on the description format of the three-dimensional shape model of the three-dimensional graphic system.

(Combination of Watermark Shapes) The created watermark shape 200 is composed of vertices having the same coordinate values as the vertices of the polygon in FIG. Since the direction is opposite to that of the polygon, it is defined as being pasted on the back surface of the surface 100. Next, in order for the watermark shape 200 to be always displayed together with the surface 100 on the three-dimensional graphic system, the surface 100 (FIG.
Are combined as the same node in the scene graph (redefined).

The node here is one graphic unit handled by the graphics system, and the graphics system controls whether or not to display a single node unit when displaying a certain screen. . The specific way of combining as the same node depends on the description style of the 3D shape model of the adopted graphics system,
This can also be described by a certain procedure.

(Embedding of Watermark Shapes) There are some vertices of many polygons on the surface 100 and vertices of the watermark shape 200 whose coordinate values overlap. One of these overlapping vertices is removed, and the required figure is redefined with the remaining vertices. By doing so, if all or part of the watermark-shaped figure is extracted by extracting the figure with respect to the direction of the normal vector, when the extracted figure is deleted, the original figure will always be damaged. Parts will be created.

(Setting of surface attribute of watermark shape)
The specular reflection light, diffuse reflection light, environment light, and the like of the watermark shape 200 are set to the same values and attribute values as the original three-dimensional shape.
This makes it more difficult to recognize the presence of the watermark shape 200.

Thus, the watermark shape 200 shown in FIG.
Is embedded in the original shape surface 100 as shown in FIG. FIG. 9 shows the rendering result of FIG. FIG. 9 (a)
Is the case where the viewpoint is on the surface table (Z> 1). In this case, since the watermark shape 200 is located on the back side of the surface, and the normal line is also opposite to the line of sight, it is not displayed. FIG. 9B shows a case where the viewpoint is behind the surface (Z <1). In this case, since it is the reverse of FIG. 9A, only the watermark shape is displayed. Also, if you display the wire frame, look in either direction,
Only the polygon mesh is displayed.

In order to improve the resistance of the watermark to partial modification to the original three-dimensional figure, a plurality of embedded parts are selected, and a watermark shape is created for each embedded part. What is necessary is just to embed (if the embedment part of two or more places is congruent mutually, creation of a watermark shape will be 1
Degree).

In order to check the watermark information inserted by the method of the present invention, all figures are transmitted with a transparency of 5 regardless of the orientation of the surface.
A special viewer that renders and displays at about 0% is used. In this viewer, since the transparency of the portion in which the watermark shape is embedded (the surface overlaps with the original three-dimensional shape) is different, the information embedded as the watermark appears to emerge. Such a viewer system is not generally commercially available, but can be created by those familiar with the three-dimensional CG technology.

The method of the present invention has been described above with reference to the specific example of the original three-dimensional shape data of FIG. 2 and the watermark shape 200 of FIG. In this specific example, the surface 100 (actually, a set of a large number of small polygons), which is an embedding portion, forms one plane. However, in general, a watermark is embedded. Good. In other words, the vertices forming the figure forming the embedded portion need not be on the same plane. This is because the essential idea of the present invention is to use a required number of vertices from the vertices forming the figure of the embedding portion to form a watermark shape having a surface opposite to the embedding portion (such a shape as described above). The configuration can be created interactively on a three-dimensional shape modeling system, or a dedicated program can be created that automatically configures the data by providing data of the embedded portion.) Therefore, the watermark shape cannot be detected by the wire frame display. However, in general, a watermark shape cannot be created unless the embedded portion is determined.

The three-dimensional shape modeling data created by the method of the present invention and the recording medium on which the three-dimensional shape modeling data is recorded have a surface constituting a watermark embedding portion and a normal vector in the opposite direction using the vertex of the surface. The watermark shape composed of the surface defined as above is included.

[0025]

As described above in detail, according to the method of the present invention, an invisible watermark can be embedded in a three-dimensional shape model by a simple procedure. There is no simple and practical method of inserting a digital watermark into three-dimensional shape model data. Accordingly, the present invention is directed to the act of certifying the creator of the data and duplicating the data without permission from the creator in the case of distributing digital data in a three-dimensional shape such as an electronic catalog on the Internet. Check,
This is an extremely practical and revolutionary invention that can be used as a means for preventing unauthorized copying and protecting proprietary rights.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating the procedure of the method of the present invention.

FIG. 2 is an example of a three-dimensional shape model.

FIG. 3 is an enlarged view of a surface 100 which is an embedded portion.

FIG. 4 shows character / graphic information embedded as a digital watermark.

FIG. 5 is a diagram illustrating a process of creating a watermark shape 200;

FIG. 6 shows a created watermark shape 200;

FIG. 7 shows a watermark shape 200 whose normal is inverted.

FIG. 8 is a diagram showing a state in which a watermark shape 200 is embedded in a surface 100.

FIG. 9 shows a rendering result of a figure in which a watermark shape 200 is embedded.

FIG. 10 is a flowchart illustrating the procedure of the method of the present invention.

FIG. 11 is a diagram illustrating a method of determining a normal vector of a surface and the front and back of the surface.

[Explanation of symbols]

 100 Three-dimensional watermark embedding part of embodiment 200 Watermark shape

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) 9A001 F-term (Reference) 5B046 FA06 5B050 BA09 BA18 EA19 5B057 CA13 CB13 CE08 CF10 5C076 AA12 BA06 CA02 5J104 AA14 NA27 9A001 DD15 EE02 EE03 HH29 JZ25

Claims (3)

[Claims] 1. A part of three-dimensional shape data is selected as a watermark embedding part, a required number of vertices are selected from vertices constituting the watermark embedding part, and a new vertex is copied from the selected vertex to obtain a watermarking part. A first step of forming three-dimensional shape data, a second step of inverting the direction of each surface forming the watermark shape in a direction opposite to the direction of the corresponding surface of the original three-dimensional shape data, A third step of arranging the watermark shape obtained in the second step in the embedment part of the three-dimensional shape data and joining the two, and a fourth step of removing the vertex overlapping the watermark shape and the embed part.
A method for embedding a digital watermark in a three-dimensional shape model, comprising the steps of: 2. A three-dimensional model to which a fifth step of setting a surface attribute of a watermark shape to be the same as a surface attribute of a surface of an embedded portion after the first to fourth steps is added. Digital watermark embedding method. 3. A watermark shape that shares some vertices with a watermark embedding portion that is a part of a three-dimensional shape,
A computer which records three-dimensional shape modeling data including a watermark shape defined such that an opposite surface composed of the same side is present in the watermark embedding portion on each surface constituting the watermark shape. A readable recording medium.