JP2892605B2 - Stereoscopic image generation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional image generating apparatus, and more particularly, to a three-dimensional image generating apparatus that generates a three-dimensional image according to an observer's viewpoint using fractal geometry.

[0002]

2. Description of the Related Art In the field of computer graphics, there is a motion visual display system that defines an object by a three-dimensional model, measures the position of a user's viewpoint, and generates and displays an image viewed from the viewpoint through a screen. Is being developed. Systems for simulating natural landscapes have also been developed. Furthermore, using the wide field of view, high definition, stereoscopic vision, and motion vision, immersive communication that can provide a sense of being in a remote place as if in the same space has been developed.

In computer graphics, when an object to be displayed is defined by a three-dimensional model and a high-quality image is generated, the object is finely sampled, a light source is calculated, and a perspective display is performed. A realistic image can be obtained. Further, when stereo display, motion visual display, and the like are performed, the stereoscopic effect of the displayed image is further enhanced. When such a high-quality image is generated, the number of vertices of a required display model becomes enormous, so that the amount of calculation such as a rendering process and a projection conversion process increases, which tends to increase the processing time. .

In the above-mentioned immersive communication conference system, it is required to generate and display a high quality image in real time. For this reason, various researches have been conducted to improve the processing speed of computers, develop high-speed algorithms for various processes such as light source calculation, create models that eliminate vertices using visual characteristics, and display using the models. I have.

By the way, in order to display a shape having an enormous amount of data such as a tree, it is necessary to delete the number of vertices of the display model using visual characteristics. However, it has not been possible to reduce the data amount to such an extent that an image can be displayed in real time by the conventionally proposed method. In addition, a method has been proposed in which a texture obtained by parallel projection of a three-dimensional model is registered in advance, and the texture is mapped in real time to a polygon formed by a plurality of intersecting planes. The image is distorted. Furthermore, with this method, it was impossible to generate a deformation in accordance with a physical law such as fluctuation due to wind or the like in real time.

[0006] In contrast, IEICE Transactions D-II, Vol. J78- D -I
I, No. No. 7, pages 1091 to 1104, a “hierarchical tree using fractals” that displays a binocular stereoscopic image without distortion with respect to viewpoint movement and allows real-time deformation according to the laws of physics. High-speed three-dimensional tree image generation method by shape representation "has been proposed. In this method, an object having a complicated shape such as a tree is modeled using fractal geometry, and the surface is determined to have sufficient roughness for display according to the distance from the observer's viewpoint to the object. Accordingly, a simplified model is generated, and the texture of the tree image from an appropriate viewpoint is mapped to the simplified model.

[0007]

However, in this method, since texture information on a complicated portion of a tree is not prepared, a complete stereoscopic image cannot be displayed when the complicated portion is exposed due to deformation. was there. Also, there is a problem that about 18 tree images are required to display a binocular stereoscopic image without distortion with respect to a viewpoint movement over 360 degrees around the tree. At this time, one tree image can correspond to a viewpoint movement of about 20 °.

Accordingly, it is an object of the present invention to provide a stereoscopic image generating apparatus capable of generating an accurate stereoscopic image even when an object having a complicated shape is deformed and a complicated part is exposed.

[0009]

According to the present invention, a three-dimensional image generating apparatus for generating a three-dimensional image according to an observer's viewpoint models an object to be generated as a three-dimensional image using fractal geometry. A fractal model generating means for generating a fractal model by the method, and a simplified model generating means for generating a plurality of simplified models having a definition corresponding to a distance from an observer's viewpoint to an object based on the fractal model. A partial texture generating means for generating a plurality of partial textures for each simplified model by projecting a corresponding portion of the fractal model onto each of the elements constituting each of the simplified models, and an externally provided observation A simplified model selecting means for selecting a corresponding one of the simplified models in accordance with viewpoint data relating to the viewpoint of the observer; Comprises a portion texture selecting means for selecting a plurality of portions texture corresponding to the selected simplified models according to the data, and a mapping means for mapping the plurality of partial textures selected by the selected simplified models.

Therefore, according to the present invention, even if the intricate part of the object is exposed by the deformation according to the laws of physics, a plurality of partial textures are individually provided for all the elements constituting each simplified model. , It is possible to always display a complete binocular stereo image without missing the exposed intricate part, and to display the entire circumference of the tree compared to the conventional method described above. Therefore, the amount of data required can be greatly reduced.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of a motion visual display system including an image generation unit according to the present invention. Referring to FIG. 1, the motion visual display system includes a screen 12 for displaying an object 14.
And a magnetic sensor 20 for detecting the viewpoint of the observer 18
A magnetic field generating unit 16 for generating a predetermined magnetic field; an image generating unit 24 for generating an image of the object 14 to be displayed on the screen 12; a magnetic field generating unit 16 and the image generating unit 2
4 in response to the output of the magnetic sensor 20.
And a control unit 22 that supplies viewpoint data relating to eight viewpoints to the image generation unit 24.

A three-dimensional world coordinate system in this motion visual display system is defined by an xyz coordinate system 10. First, the screen 12 and the object 14 in this three-dimensional world coordinate system
And the three-dimensional position of the magnetism generating section 16 is obtained in advance.
A magnetic sensor 20 is mounted on the head of the observer 18. The magnetic sensor 20 detects a magnetic field generated by the magnetic field generator 16, whereby the distance from the magnetic field generator 16 to the viewpoint of the observer 18 is obtained in real time.
In response to the output of the magnetic sensor 20, the control unit 22 supplies viewpoint data relating to the viewpoint of the observer 18 to the image generation unit 24.

In the embodiment shown here, the magnetic sensor 20 is used to detect the viewpoint of the observer 18, but this does not limit the method of detecting the position of the viewpoint. Any method of detecting position can be employed.

When the viewpoint 18 of the observer 18 and the positional relationship between the screen 12 and the object 14 are determined in this way, a perspective projection image obtained by observing the object 14 from the viewpoint through the screen 12 is generated by the image generation unit 24. Are displayed on the screen 12. For example, observer 18
Moves to the right, the right side of the object 14 that can be observed from the new right viewpoint is displayed on the screen 12. On the other hand, when the observer 18 moves to the left, the left side of the object 14 that can be observed from the new left viewpoint is displayed on the screen 12.

In order to display a stereoscopic image in real time in accordance with the viewpoint of the observer, a model serving as a skeleton of the object 14 to be displayed and a texture or the like to be attached to the model are required. It must be prepared in advance. FIG. 2 is a block diagram showing an apparatus for generating a model and a texture necessary for displaying an object having a complicated shape such as a tree. Referring to FIG. 2, the apparatus includes a fractal model generation unit 261 that generates a fractal model by modeling an object having a complex shape such as a tree using fractal geometry, and a fractal model generated by the fractal model. Hierarchical simplified model generation unit 262 that generates a plurality of simplified models 281 based on
And a hierarchical partial texture generation unit that generates a plurality of partial textures 301 for each simplified model by projecting a corresponding portion of the generated fractal model onto each of the elements constituting each simplified model. 263
A texture management table generation unit 264 that generates a texture management table 302 for managing which element in which simplified model the generated partial texture corresponds to, and a generated simplified model , The generated partial texture 301 and the management table 30
And a database 30 for storing the data.

The tree to be displayed is modeled by the fractal model generation unit 261 using fractal geometry, thereby generating a fractal model including shape data with the highest definition. By using the data of the fractal model, a tree 261a having a three-dimensional shape with the highest definition as shown in FIG. 3 can be displayed.

Next, the hierarchical simplified model generator 262 generates three simplified models 281 based on the generated fractal models. Here, as shown in FIG. 4, three simplified models 281a to 281c having different degrees of definition are generated according to the distance from the viewpoint of the observer 18 to the tree, which is the object 14. In general, there is a visual characteristic that a tree closer to the viewpoint can be observed in detail, and a tree farther from the viewpoint can be roughly observed. For this reason, high-definition shape data is required for trees located near the viewpoint, but not so high-definition shape data is required for trees located far from the viewpoint.

Therefore, here, as shown in FIG. 4A, a simplified model 281 having a high definition is used as data for displaying a tree close to the viewpoint.
a is generated based on the fractal model. Further, as shown in FIG. 4B, a simplified model 28 having a medium definition is used as data for displaying a tree at a medium position that is not so close or far from the viewpoint.
1b is generated based on the fractal model. Further, as shown in FIG. 4C, a simplified model 281c having a low definition is generated based on the fractal model as data for displaying a tree far from the viewpoint. The three simplified models 281 (281a to 281c) thus generated are stored in the database 2
8 is stored.

FIG. 5 shows the data structure of the simplified model 281 in a database. As shown in FIG.
The data of the simplified model 281 includes a branch data structure 40 and a leaf data structure 50. The branch data structure 40 is
It has a pointer 41 to a child branch, a range 42 of descendant branches, simplified shape data 43, a texture identifier 44 for simplified shape data, and branch shape data 45. The leaf data structure 50 has leaf shape data 51. The shape roughness due to the distance from the viewpoint and the range 42 of the descendant branch are compared in order from the original trunk 46 to the child branch 47. Range of offspring branches 4
When 2 is smaller than the above-mentioned shape roughness, the simplified shape data 43 at that time is used instead of drawing the subsequent shape data.

On the other hand, the hierarchical partial texture generator 263
In, the partial texture 301 is generated for the elements 32 configuring each of the simplified models 281a to 281c. As shown in FIG. 3, one element 32 constituting the simplified model 281a is selected, and the corresponding part 34 of the tree 261a with the highest definition using the fractal model is selected. A corresponding portion 34 of the fractal model is projected onto the selected element 32,
Thereby, one partial texture 301 is generated.
Similarly, a plurality of partial textures 301 corresponding to all the elements 32 of the simplified model 281a are generated.

Each element 32 of the simplified model 281 is composed of a cross-shaped polygon. Therefore,
Texture 301 is obtained by projecting a corresponding model of fractal model 261a parallel to each of the polygons. In addition, four types of data corresponding to the front, rear, left and right of the simplified model 281 are used as texture data.

The vertical and horizontal size Text of the texture is determined according to the following equation (1). Text = Tree × A ^B (1) Here, “Tree” is a vertical and horizontal size of a tree assumed when displaying computer graphics. A is represented by the following equation (2). A = 1 / √C (2) B is the generation of the branch for simplification, and C is the IFS
Is the number of reduced maps of. The data amount for this required C ^B-number of the simplified model by the texture can be the following equation (3). ^{Stex 2 × C B × 4 =} Stree 2 × 4 ... (3) Here, the relationship between the level B of the vertical and horizontal sizes Stree and simplification of trees to be assumed at the time of display of the computer graphics and the following equation (4) I do. 0 ≦ B ≦ E−1,
Larger B indicates higher definition. Tree = Smax × D ^EB (4) where Smax is the maximum vertical and horizontal size of the tree assumed when displaying the computer graphics, D is the average of the reduction ratio of each reduced map, and E is the maximum. This is the generation of branches when giving definition. According to the equation (4), the size of the simplified shape on the display surface is constant regardless of the size Tree. The amount of texture data required at this time is represented by the following equation (5).

[0023]

(Equation 1)

If, for example, D = 0.5 and E = 8 are given as typical values in the equation (5), the required texture data amount is Smax ² × 5.074.

In this way, a plurality of partial textures 301 are individually generated for each simplified model 281. However, since a large number of partial textures are generated, each level of the partial textures corresponds to the simplified model 281a-281. 281
c, and which element of the simplified model should be managed. The management table for managing such a partial texture is generated by:
This is the texture management table generation unit 264 shown in FIG.

As shown in FIG. 6, the generated partial textures are grouped for each layer and are referred to by a texture identifier 44 for simplified shape data uniquely defined in each group. The simplified shape data texture data management table 60 stores the simplified shape data texture identifier 44 in the offset 63 in the grouped image data 62 and the vertical and horizontal sizes 64 and 65.
.

The partial texture 31 and the management table 302 thus generated are stored in the database 30. Thereby, all the partial textures 301 necessary for the simplified model 281 stored in the database 28 are prepared, and all the partial textures 301 are further prepared.
Corresponds to which element of which simplified model is prepared.

FIG. 7 shows details of the image generation unit 24 for generating a stereoscopic image according to the viewpoint of the observer 18 in real time based on the simplified model 281, the partial texture 301, and the management table 302 stored in the database. FIG. Referring to FIG. 7, this image generation unit 24
Is selected by the simplified model selection unit 241 that selects the corresponding one of the simplified models 281 according to the viewpoint data from the control unit 22 and the simplified model selection unit 241 according to the viewpoint data from the control unit 22 A partial texture selecting unit 242 for selecting a plurality of partial textures corresponding to the simplified model thus selected, and a plurality of partial textures selected by the partial texture selecting unit 242 for the simplified model selected by the simplified model selecting unit 241. A rendering processing unit 243 that performs mapping in accordance with the management table 302.

Therefore, the simplified model selecting section 241 selects one of the three simplified models 281a to 281c stored in the database 28. If the distance from the viewpoint of the observer 18 to the tree that is the object 14 is short, the simplified model 281a with high definition shown in FIG. 4A is selected. If the distance from the observer 18 to the tree, which is the object 14, is moderate, FIG.
The simplified model 281b having the medium definition shown in (b) is selected. If the object 1 from the observer 18
If the distance to the tree of No. 4 is long, the simplified model 281c with low definition shown in FIG. 4C is selected.

On the other hand, in the partial texture selecting section 242,
From the partial textures 301 stored in the database 30, a plurality of partial textures 301 corresponding to the simplified model selected by the simplified model selection unit 241 are selected. If the simplified model selecting unit 241 selects the simplified model 281a with high definition shown in FIG. 4A, all the partial textures 301 corresponding to the selected simplified model 281a are selected. You.

In the rendering processing unit 243, a corresponding one of the selected partial textures is mapped to each element 32 of the simplified model 281 selected according to the management table 302 stored in the database 30. Thereby, data necessary for three-dimensional display of the tree is supplied to the screen 12, and a three-dimensional image of the tree is displayed on the screen 12.

As described above, according to this embodiment, since tree shape data corresponding to the distance from the viewpoint is used for drawing, it is necessary to draw a large amount of tree data such as a landscape simulation. Even in this case, the display image can be changed in real time with respect to the movement of the viewpoint. Therefore, it is possible to display a binocular stereoscopic image without distortion due to the movement of the viewpoint. In addition, because the texture is generated by projecting the corresponding parts of the fractal model to each element of the simplified model, not the entire simplified model, the tree is deformed according to physical laws such as fluctuation due to wind etc. Therefore, even if the intricate part is exposed, it can be naturally displayed by the texture of the newly exposed part due to the deformation.

Also, in the above-described conventional method, about 18 tree images are required to display a binocular stereoscopic image free from distortion with respect to a 360-degree viewpoint movement over the entire tree. On the other hand, in this embodiment, the entire circumference of the tree can be displayed with a data amount equivalent to about five tree images even at a relatively high level of simplicity, so that the required data amount can be greatly reduced. .

Therefore, in motion visual display using computer graphics, by generating shape data with roughness corresponding to the viewpoint position, even when a large number of trees must be displayed, such as in a landscape simulation, real-time display is possible. Can be used for drawing. In addition, even if the shape of the tree image is simplified to the extent that real-time display is possible by texture-mapping the tree image to the simplified shape, the color tone of the original tree is maintained while maintaining the three-dimensional tree image. Can be displayed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a motion visual display system including a stereoscopic image generation device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a part of the three-dimensional image generating apparatus according to the embodiment of the present invention, which is a part for preparing data necessary for an image generating unit in FIG.

3 is an explanatory diagram illustrating a method of generating a partial texture for each element of each simplified model in a hierarchical partial texture generation unit in FIG. 2;

FIG. 4 is a diagram showing a simplified model generated by a hierarchical simplified model generation unit in FIG. 2 according to a distance from a viewpoint.

FIG. 5 is an explanatory diagram showing a hierarchical model of a simplified model generated by a hierarchical simplified model generation unit in FIG. 2;

FIG. 6 is an explanatory diagram showing a method of generating a partial texture and a management table in a hierarchical partial texture generation unit and a texture management table generation unit in FIG. 2;

FIG. 7 is a block diagram showing a detailed configuration of an image generation unit in FIG. 1 and its periphery.

[Explanation of symbols]

 24 image generating unit 28, 30 database 241 simplified model selecting unit 242 partial texture selecting unit 243 rendering processing unit 261 fractal model generating unit 262 hierarchical simplified model generating unit 263 hierarchical partial texture generating unit 264 texture management table generating unit 281 , 281a to 281c Simplified model 301 Partial texture 32 elements

Continuation of the front page (72) Inventor Shinichi Shiwa Kyoto Prefecture Soraku-gun Seika-cho Oaza Inaya small character Sanraya 5 Inside ATI Communication System Research Laboratories (56) References IEICE Transactions, VOL . J 78-D-II, NO. 7, pp 1091-1104, issued July 25, 1995 (58) Fields investigated (Int. Cl. ⁶ , DB name) G06T 15/00-17/50 H04N 13/02

Claims (1)

(57) [Claims] 1. A three-dimensional image generating apparatus for generating a three-dimensional image according to a viewpoint of an observer, wherein a fractal model is generated by modeling an object to be generated as the three-dimensional image using fractal geometry. A fractal model generating unit that generates, based on the fractal model, a simplified model generating unit that generates a plurality of simplified models having a definition corresponding to a distance from the viewpoint of the observer to the object. Texture generating means for generating a plurality of partial textures for each simplified model by projecting a corresponding portion of the fractal model onto each of the elements constituting each of the simplified models; A simplified model selecting means for selecting a corresponding one of the simplified models in accordance with viewpoint data relating to the viewpoint of the user Partial texture selecting means for selecting a plurality of partial textures corresponding to the selected simplified model according to the viewpoint data; and mapping the selected plurality of partial textures to the selected simplified model. A three-dimensional image generation device including a mapping unit.