JP6110773B2 - 3D map data generation system - Google Patents

Description

  The present invention relates to a three-dimensional map data generation system that generates three-dimensional map data including a three-dimensional model representing a three-dimensional shape of a building.

In a three-dimensional map that three-dimensionally displays features such as buildings and roads, a three-dimensional model representing the three-dimensional shape of these features is used. The three-dimensional model is generated for each feature by an operator's manual input or the like, and is generated by individually pasting a texture representing the appearance of the feature on the surface.
However, there are many buildings represented on a three-dimensional map, and if a three-dimensional model is generated individually for all buildings, the work load required for the generation becomes great. Various techniques for automatically generating a three-dimensional model have been proposed in order to reduce the workload for generating such a three-dimensional model. As an example, Patent Document 1 discloses a technique of generating a three-dimensional model by translating a building frame, that is, a planar shape of a building in the height direction, and attaching a texture to the surface. In addition, when pasting a texture, the side of the building to be processed is judged to be the side with the maximum distance to the surrounding building as the front, and the texture that indicates the entrance is pasted here Also disclosed.

JP 2007-149108 A

Since the advantage of a 3D map is that it is easy for the user to intuitively grasp the geography, improving the reality of the 3D model is one of the important issues in the 3D map. The texture that is affixed to the side of the building is not necessarily the same on all sides, but the side with a window, the side that is a wall, etc. It is preferable to use them properly. Patent Document 1 only proposes a technique related to a front discrimination method, and discloses only a method in which an operator manually selects a texture to be used for other aspects.
Since the appearance of the building, such as which side of the building has windows, depends on the shape of the building, it is necessary to analyze the shape of the building in order to use different textures for each side. However, the shape of the building is not uniform, and there are a wide variety even if only the planar shape is taken. Therefore, it is not easy to establish a general-purpose shape analysis method.
The proper use of the texture for each side of the building is a problem that can also occur when a texture is automatically applied to a three-dimensional model generated by an operator's manual input or the like.
In view of these problems, an object of the present invention is to provide a technique that enables the proper use of texture with high reality by analyzing the shape of a building.

The present invention
A 3D map data generation system for generating 3D map data including a 3D model representing a 3D shape of a building,
A texture database storing a plurality of types of textures to be pasted on the side of the three-dimensional model;
A building frame shape analysis unit that obtains a centerline by thinning a building frame that is a planar shape of the building;
Based on the positional relationship between the center line and the side of the 3D model of the building, a 3D map data generation system including a texture setting unit that sets a texture to be pasted on the side from the texture database. Can do.

Thinning is an image processing technique for obtaining a center line of a two-dimensional closed figure. By thinning the building frame, the characteristics of the shape of the building frame can be represented by the center line. For example, in the case of a rectangular building, since the center line along the longitudinal direction is obtained by thinning, the longitudinal direction can be easily specified without comparing the widths of the side surfaces. In addition, for buildings having an L-shaped planar shape, an L-shaped center line can be obtained by thinning, so it is relatively easy to determine whether it is bent at one place and how many times its angle is. Can be easily identified. Thus, thinning the building frame is very useful for grasping the characteristics of the planar shape of the building.
In the present invention, since the texture is set based on the positional relationship with the center line representing the characteristics of the planar shape of the building as described above, it is possible to easily realize proper use according to the shape of the building.

Here, the correlation between the shape of the building and the appearance will be described.
FIG. 1 is an explanatory view showing an example of the appearance of a residential building, that is, an apartment, a housing complex, an apartment, and the like. In the residential buildings shown in the columns (a) to (c) of FIG. 1, openings such as passages and verandas are mainly provided on the plane in the longitudinal direction of the flat rectangular building, and the plane in the short direction. It can be seen that there are mainly walls. In the buildings shown in columns (d) and (f) of FIG. 1, it can be seen that stairs are provided at two or three protruding portions on the longitudinal surface. In the building in column (e), the difference in length between the longitudinal direction and the lateral direction is relatively small, and thus it can be seen that openings are provided on either surface. These features are all correlated with the planar shape of the building.
FIG. 2 is an explanatory diagram showing an example of the appearance of an office building. In the buildings in columns (a) and (b) of FIG. 2, openings such as windows are mainly provided in the longitudinal surface of the flat rectangular building, and walls are mainly formed in the lateral surface. It can be seen that an auxiliary window of the same level as the light is provided. In the buildings in columns (c) and (d) of FIG. 2, windows are provided on the rectangular short-side surface for convenience of arrangement with adjacent buildings. All of these features are correlated with the planar shape of the building, and in the case of office buildings, it is better to consider the relationship with adjacent buildings as shown in columns (c) and (d) of FIG. It shows that it may be.
FIG. 3 is an explanatory diagram showing an example of the appearance of a school building and a warehouse. According to the image of the school building shown in the columns (a) to (d) of FIG. 3, it can be seen that an opening such as a window is provided on the surface along the center line even when bent in an L shape or the like. . Further, as shown in the column (d), it can be seen that there is a structure such as a passageway connecting the school building and the school building.
In the case of a warehouse as shown in columns (e) and (f) of FIG. 3, although an entrance such as a shutter is provided in the longitudinal direction, an opening such as a window is not provided, and light is taken in the short direction. It can be seen that a smaller window is provided.
As described above, FIGS. 1 to 3 show only examples of buildings, but it is understood from these examples alone that there is a correlation between the appearance of the building and the planar shape of the building, that is, the building frame. Therefore, if the texture representing the appearance is properly used based on the building frame, it is possible to give the three-dimensional model an appearance close to such a real building.
In the present invention, the positional relationship between the center line and the side surface can be variously set. For example, the texture may be set according to the side surface substantially parallel to the center line or the side surface intersecting, that is, the angle between the center line and the side surface. Further, the texture may be properly used depending on the distance from the center line to the side surface. Furthermore, the texture may be properly used depending on the shape of the center line itself and the length of the center line.
The texture setting in the present invention does not need to be performed for all buildings, and may be performed for some buildings included in the three-dimensional map data. Furthermore, when applying the present invention, in addition to the positional relationship between the center line and the side surface, the direction of the side surface, the positional relationship with the road or surrounding buildings, and the like may be considered.

In the three-dimensional map data generation system of the present invention,
The texture setting unit may switch a selection pattern for selecting the texture based on at least one of the shape of the center line and the length of each line segment constituting the center line.
As illustrated in FIGS. 1 to 3, the shape of the building is various, and the selection pattern of what texture to be applied to which side changes depending on the shape. For example, even if a building is bent or protruded, it may be a staircase as shown in columns (d) and (f) of FIG. 1, or in columns (b) and (c) of FIG. ) In some cases, an opening such as a window and a wall are provided. As described above, the relationship between the shape of the building and the texture cannot be expressed by a single rule.
In the above aspect, since the texture selection pattern is switched according to the shape and length of the center line, it is possible to use different textures according to the selection pattern according to the characteristics of the shape of the building. It is possible to realize proper use.

In the 3D map data generation system of the present invention,
The three-dimensional model is attached with type information indicating the type of the building,
The texture setting unit may switch a selection pattern for selecting the texture according to the type of the building.
As shown in columns (e) and (f) of FIG. 3, for example, in a warehouse, unlike other buildings, no windows are provided on the surface in the longitudinal direction. Thus, even in the case of a rectangular building, the proper use of texture differs depending on the type of building. According to the said aspect, since the selection pattern according to the kind of building is realizable, the various usage close | similar to a real building can be implement | achieved more.
In addition, the residential building shown in FIG. 1 has a veranda in the opening, whereas the office building shown in FIG. 2 has an appearance in which windows are arranged in order without a veranda. Thus, even one opening such as a window has a different appearance depending on the type of building. In the said aspect, according to the kind of building, a texture can also be used properly and the external appearance close | similar to a real building can be implement | achieved.

In the three-dimensional map data generation system of the present invention,
The building frame shape analysis unit groups the line segment group as a straight line when the interior angle formed by the line segment constituting the center line is an obtuse angle of a predetermined value or more,
The texture setting unit may set the texture based on the grouping.
In the present invention, the feature of the planar shape of the building is grasped by the center line of the building frame obtained by thinning. However, since the planar shape of the building is diverse, the obtained center line itself is also diverse.
According to the above aspect, since the line segments connected at an obtuse angle can be handled as forming a straight line, the features of the planar shape can be grasped more simply than when handled as individual line segments. . Therefore, there is an advantage that it is possible to simplify the pattern for properly using the texture.
In addition to the above processing, for example, the connection state between the line segments may be classified into a predetermined number of groups prepared in advance. For example, a case where two line segments are connected at about 90 degrees is expressed as “bending”, and a case where three or more lines are connected at about 90 degrees is expressed as “branching”. If the shape of the center line is expressed, the texture selection pattern can be further simplified, and the process of proper use can be made more efficient.

In the three-dimensional map data generation system of the present invention,
The texture setting unit may set an opening texture representing an opening for a side surface substantially parallel to the center line.
Looking at the examples of various buildings shown in FIGS. 1 to 3, the longitudinal direction of the rectangular portion, that is, the side surface substantially parallel to the center line, is provided with openings such as passages, windows, and verandas. In many cases, it is understood that such a side surface is not an opening, such as a warehouse. Therefore, if an opening texture is provided on such a surface as one selection pattern for properly using the texture, it is possible to realize an appropriate texture for many buildings.

In the three-dimensional map data generation system of the present invention,
As pre-processing for setting the texture, a three-dimensional model generation unit that generates the three-dimensional model based on the building frame may be provided.
The present invention can be applied to a case where textures are automatically set for a three-dimensional model prepared by manual input by an operator. However, if a three-dimensional model is automatically generated and applied, the processing load is further increased. There is an advantage of lightening.
Further, since the automatically generated three-dimensional model has a relatively uniform shape, there is an advantage that the texture can be pasted without complicated processing.
As a method of automatically generating a three-dimensional model, a method of starting a building frame, that is, a method of translating in the height direction, or a method of deforming a basic three-dimensional shape, also called a primitive prepared in advance, together with the building frame Etc. are considered.

In the present invention, it is not always necessary to provide all of the above-described features, and some of the features may be omitted or combined as appropriate.
In addition, the present invention may be configured as a 3D map data generation method for generating 3D map data by a computer, or may be configured as a computer program for causing a computer to execute such data generation. You may comprise as a computer-readable recording medium which recorded such a computer program.

It is explanatory drawing which shows the example of an external appearance of a residential building. It is explanatory drawing which shows the example of an external appearance of an office building. It is explanatory drawing which shows the example of an external appearance of a school building and a warehouse. It is explanatory drawing which shows the structure of a three-dimensional map data generation system. It is explanatory drawing which shows the structure of 2D map DB. It is explanatory drawing which shows the structure of 3D map DB. It is explanatory drawing which shows the structure (1) of texture DB. It is explanatory drawing which shows the structure (2) of texture DB. It is explanatory drawing which shows the structure (3) of texture DB. It is a flowchart (1) of 3D map data generation processing. It is a flowchart (2) of 3D map data generation processing. It is a flowchart (3) of 3D map data generation processing. It is explanatory drawing which shows the example of a production | generation of a three-dimensional model.

A. System configuration:
FIG. 4 is an explanatory diagram showing the configuration of the three-dimensional map data generation system. The 3D map data generation system is a system for generating a 3D model of a feature by an operator's operation or automatically. In the present embodiment, the system is configured as a stand-alone system by a computer incorporating a CPU, RAM, ROM and the like, but may be configured by connecting a plurality of servers and the like via a network. The various functional blocks shown in the figure are configured by software by installing software for realizing each function in a computer, but a part or all of the functional blocks may be configured by hardware.
The three-dimensional data generation system also includes a functional block for generating a three-dimensional model by an operator's operation, but this is not shown in this embodiment. In the figure, portions related to the function of automatically setting the texture are shown.
The three-dimensional model is generated in two stages, in which a three-dimensional shape of a building is modeled and a texture is pasted. In the following description, to clearly represent this process, the state before applying the texture is referred to as “three-dimensional polygon”, and the state in which the texture is further set is referred to as “three-dimensional model”.

The contents of each functional block provided in the 3D map data generation device will be described.
The two-dimensional map DB (database) 16 stores plane map data. In this map data, the planar shape of each feature is represented by polygons. In this specification, the planar shape of a building is called a building frame.
The three-dimensional map DB (database) 17 stores data of a three-dimensional map that three-dimensionally represents the shape of the feature. The three-dimensional map data is composed of a three-dimensional model for each feature, and this three-dimensional model is composed of three-dimensional polygons representing the three-dimensional shape of each feature, and pasted texture data.
The texture DB (database) 18 stores texture image data used in the embodiments. In order to automatically paste the texture onto the side surface of the three-dimensional polygon of the building, the texture DB stores the texture according to the texture selection pattern. Its structure will be described later.

The command input unit 11 inputs a command related to the generation of 3D map data based on the operation of the operator. In the present embodiment, for example, a command for designating a region for generating a three-dimensional model is included.
The processing target specifying unit 12 refers to the three-dimensional map DB 17 and the two-dimensional map DB 16 to specify a processing target, that is, a three-dimensional polygon that should be a target to which a texture is automatically pasted.
The 3D polygon generation unit 13 generates a 3D polygon to be processed based on the building frame stored in the 2D map DB 16.
The building frame shape analysis unit 14 analyzes the shape of the building frame based on the building frame stored in the two-dimensional map DB 16. In this embodiment, the building frame is thinned to obtain a center line, and analysis is performed based on the center line. The analysis method will be described in detail later.
The texture setting unit 15 selects a texture from the texture DB 18 based on the analysis result obtained by the building frame shape analysis unit 14 and pastes it on each side surface of the 3D polygon generated by the 3D polygon generation unit 13. . However, as the processing on the database, only the image data of the texture is associated with each side surface. Therefore, in this embodiment, this processing is sometimes called setting.
The three-dimensional model generated by the above processing is stored in the three-dimensional map DB 17. Therefore, by executing the processing by the above-described functional blocks for various processing targets, textures can be set for all buildings, and the three-dimensional map DB 17 can be completed. The completed 3D map DB 17 is stored in the server SV via a network or a recording medium, and further transmitted to various portable terminals SP and the like via the network NE and used for displaying a 3D map.

B. 2D map DB:
FIG. 5 is an explanatory diagram showing the configuration of the two-dimensional map DB 16. The two-dimensional map DB 16 stores data for displaying the two-dimensional map illustrated on the upper side of FIG. 5, that is, polygon data and character data of various features such as buildings and roads. In the figure, a building frame, that is, a planar shape, is shown with a border on a part of the building. It can be seen that there are a wide variety of building frames.
In the lower part of FIG. 5, the data structure of the two-dimensional map DB 16 is illustrated. The data shown is prepared for each feature. The “feature ID” is identification information unique to the feature data. “Type” is information representing the type of the feature. In this embodiment, the building is information that can also specify the type of building, such as “office building”. “Name” is the name of the feature. The “shape” is a polygon shape for displaying a feature. In this embodiment, a coordinate string of each vertex of the polygon is stored. “Height” is one piece of attribute information included in the feature of the building, and represents the number of floors of the building. In addition to this, various information may be included in the attribute of the feature.

C. 3D map DB:
FIG. 6 is an explanatory diagram showing the configuration of the 3D map DB 17. The three-dimensional map DB 17 stores data for displaying the three-dimensional map illustrated on the upper side of FIG. 6, that is, a three-dimensional model and character data representing the three-dimensional shape of each feature such as buildings and roads. . The 3D map DB 17 on the upper side of FIG. 6 is in an incomplete state, and an example is shown in which a 3D model is generated only for some buildings by the operation of the operator. As for the hatched building, a three-dimensional model has not been prepared yet, and the building frame is registered. By executing the 3D map data generation process in the present embodiment, a 3D model can also be generated for these buildings.
The lower part of FIG. 6 illustrates the data structure of the three-dimensional map DB 17. The data shown is prepared for each feature. Each data of “feature ID”, “type”, “name”, and “height” has the same contents as the two-dimensional feature DB 16. In this embodiment, for the same feature, the “feature ID” common to the two-dimensional feature DB 16 and the three-dimensional feature DB 17 is used, but different “feature IDs” are used. May be. When using different “feature IDs”, it is desirable to store information that links the two-dimensional feature DB 16 and the three-dimensional feature DB 17.
The “shape” data in the 3D map DB 17 represents the shape of the 3D model. Therefore, the three-dimensional coordinate sequence of the vertices of the polygon constituting the three-dimensional model is stored. “Texture” is information for specifying a texture used in the three-dimensional model. In this embodiment, the identification information (TEX001, TEX002, etc.) attached to the texture image stored in the texture DB 18 is stored. It is preferable that information such as the pasting position of each texture and the number of repetitions is associated with each identification information.

D. Texture DB:
7-9 is explanatory drawing which shows the structure of texture DB18. The contents of the texture DB 18 are shown in a table format.
In this embodiment, the texture on each side of the three-dimensional polygon of the building is properly used based on the shape of the center line obtained by thinning the building frame. The texture DB 18 determines which texture is to be pasted on which side according to the centerline shape, that is, the image data of the texture to be pasted on the building polygon, and the rules for pasting it (hereinafter referred to as “selected pattern”). I sometimes remember). In this embodiment, as shown in the figure, the selection pattern differs depending on the center line shape and the type of building.

The center line shape was classified by the number of three elements: straight line, bend, and branch. Bending means a bend of approximately 90 degrees such as an L-shape, and branching means a portion where three or more line segments intersect, such as an E-shaped central portion. FIG. 7 shows an example in which the building frame is rectangular. When this building frame is thinned, a straight center line is obtained as shown. This shape can be expressed as “straight line = 1, bending = 0, branch = 0”.
The “longest part” represents the longest line segment or line segment group among the line segment groups constituting the center line. Further, the “bent (branch) portion” represents a classification based on the length of a line segment constituting the bend or branch. In the example of FIG. 7, since there is only one line segment constituting the center line, no data is stored in the “longest part” and “bent (branch) part”.
Texture selection patterns are prepared according to building types. In the example shown in the figure, in the case of “office building”, the texture representing the window as the opening surface is pasted to the parallel plane, and the texture representing the wall and the lighting is pasted to the intersection plane. Yes. A parallel plane means a plane substantially parallel to the center line. Judgment is made under the condition that the normal of the center line and the wall is 90 ± α degrees (α can be arbitrarily set). The intersecting surface refers to a surface that intersects with the center line, and includes not only an orthogonal surface but also an obliquely intersecting surface. All but the parallel planes may be treated as intersection planes.
In the present embodiment, the texture is prepared in the minimum unit constituting the side of the building. In the case of an office building, as shown in FIG. 2, since the window is often arranged in order on the parallel plane, one window, which is the smallest unit, is used as the texture. In addition, the intersection plane has a wall as a main part and has many appearances provided with a light source. Therefore, the wall and one light source are used as a texture as the minimum unit. By doing so, there is an advantage that one texture can be commonly used for various buildings by adjusting the number of repeated textures according to the sizes of the parallel plane and the intersecting plane. Of course, the entire side surface or one floor may be prepared as a texture, or a texture of only a wall with no light from the intersection may be prepared. In addition, regarding the intersection plane, a texture may not be prepared, and the three-dimensional polygon may be filled with a single color or a predetermined pattern.
In the example of FIG. 7, only one type of texture for an office building is shown. However, a plurality of types of textures are prepared, and the number of floors of the office building, the area of the building frame, the aspect ratio of the building frame, that is, the longitudinal direction and the short side. Depending on the direction ratio, the texture may be used properly. Further, a plurality of types of parallel planes and intersection planes may be prepared and used in accordance with the direction of each side, the positional relationship with roads and other buildings, and the like. The same applies to the other selection patterns described below.
FIG. 7 shows an example of an apartment and a warehouse in addition to an office building. In the case of a condominium as well, textures are prepared for the parallel plane and the intersection plane as illustrated. In the condominium, the texture of the opening surface is used for the parallel plane, but the texture representing the veranda is used for the office building, which is a window. Although FIG. 7 shows an example in which a wall and a texture of lighting are used for the intersection plane, as in the office building, only the wall may be used. On the other hand, in the warehouse, a texture representing the appearance of the shutter is used instead of the opening surface for the parallel surface. Although the illustration of the intersection plane is omitted, a wall and a light texture can be used. As described above, by preparing a texture selection pattern according to the building type, it is possible to realize the proper use of the texture representing the appearance characteristics of the building.

FIG. 8 shows an example of an L-shaped building. In the case of such a building, the center line is two line segments LA and LB connected at approximately 90 degrees. Therefore, it can be expressed as “straight line = 2, bending = 1, branch = 0”. The angle between the line segments LA and LB classified as bent does not need to be strictly limited to 90 degrees, and may have an arbitrary width.
In the case of the L-shape, since there are two line segments, the longer one becomes the longest part by comparing these. In the example shown in the figure, the line segment LA is the longest part. When the lengths of the line segment LA and the line segment LB are equal, the longest part is “LA, LB”. When the line segment LB is longer, it may be divided into cases, or may be handled in the same manner as when the line segment LA is long.
The case where the line segment LA is the longest part is further divided into the case where the length of the “bent (branch) part” is smaller than the predetermined value THL and the other cases. The “bent (branch) part” means a line segment other than the longest part, that is, a line segment LB in the example of the figure. The predetermined value THL can be arbitrarily set, but this can be a value that serves as a criterion for determining whether or not a space for providing a room is secured at the bent (branched) portion.
An example of an apartment is shown in the figure for “Line segment LB <THL”. In this case, the texture is set in the same manner as in FIG. 7 for the parallel plane and intersection plane of LA which is the longest portion. The LB that is a bent (branched) portion is provided with a texture representing a staircase as shown in the drawing on both the parallel surface and the intersecting surface. When the length of the bent (branch) portion is short, there is a high possibility that it is a staircase, an elevator, or the like, so such a texture is used. The texture of the staircase and the like is prepared in a minimum unit, that is, the texture for the first floor, so that it can be used flexibly according to the height of the building. Although an example of an apartment is shown in the figure, other buildings can be prepared in the same manner. In hotels and high-rise apartments, elevator textures may be used instead of stairs.
Regarding “Line segment LB ≧ THL”, an example of a school building is shown in the drawing. In this case, since there is a high possibility that a room is formed in both the longest portion LA and the bent (branched) portion LB, as shown in the figure, the texture of the window as the opening is used for the parallel surface, and the wall is used for the intersection surface. And the light texture is used.
In the example shown in the figure, the line segment LA is the longest part. However, when the lengths of the line segments LA and LB are the same, textures for the parallel plane and the cross plane can be similarly prepared. .

FIG. 9 shows an example of a U-shaped building. In the case of such a building, the center line is three line segments LA, LB, and LC connected at approximately 90 degrees. Therefore, it can be expressed as “straight line = 3, bend = 2, branch = 0”.
In the example of the figure, the case where the central line segment LB is the longest part and the case where the line segments LA and LC at both ends are the longest part are shown. In addition, various cases can be classified, such as when the line segment LA is the longest, and when the line segments LA, LB, and LC have the same length.
As for the case where the line segment LB is the longest part, as in the case of FIG. 8, the “bent (branch) part” LA and LC are further divided into cases where the length is smaller than the predetermined value THL and other cases, In contrast, a texture can be set.
The cases where the line segments LA and LC are the longest part can also be divided into cases where the length of the line segment LB is smaller than the predetermined value THL and other cases. In the case of “line segment LB <THL”, there is a high possibility that the portion corresponding to the line segment LB is a crossing corridor. Therefore, as shown in the example of the school building in the drawing, the texture of the crossing corridor can be prepared on the parallel plane of the line segment LB.
Thus, the texture DB 18 records the texture selection pattern according to the shape of the center line.

E. 3D map data generation processing:
10 to 12 are flowcharts of the three-dimensional map data generation process. This process is performed in cooperation with each functional block shown in FIG. 4, and is a process executed by the CPU of the 3D map data generation system in terms of hardware.
When the process is started, the CPU sets a process target area (step S10). For example, a method may be considered in which a region designated by the operator or a region in which 3D map data has not been generated is set as a processing target region.
Next, the CPU extracts a building for which a three-dimensional model has not been generated from the processing target area (step S11). In this embodiment, out of the buildings stored in the 2D map DB 16, those in which the 3D model is not stored in the 3D map DB 17 are extracted. In the present embodiment, as shown in the upper side of FIG. 6, in the 3D map DB 17, a flat building frame is stored in a building for which a 3D model has not been generated. It is possible to extract a building for which a three-dimensional model is to be generated. When all the buildings in the 2D map DB 16 are stored in the 3D map DB 17 without omission, reference to the 2D map DB 16 may be omitted.

The CPU selects one of the extracted buildings as a processing target (step S12), and generates this three-dimensional polygon (step S13). In the present embodiment, a building frame to be processed is acquired from the 2D map DB 16 or the 3D map DB 17, and a 3D model is generated by translating the building frame in the height direction as shown in the figure. The translational height H can be determined based on the building height information. Since the three-dimensional model generated by such a method has a relatively uniform shape in which at least each side surface is rectangular, there is an advantage that the texture prepared in the texture DB 18 can be easily pasted without complicated processing. .
Instead of the method of moving the building frame in parallel, a method may be used in which a basic three-dimensional model of a building called a primitive is deformed and arranged according to the building frame and height.

Next, the CPU analyzes the shape of the building frame.
First, the CPU thins the building frame and vectorizes it to obtain the center line (step S20). Thinning is a process of deleting pixels around a two-dimensional closed figure and obtaining a connected line for one central pixel. Various methods have been proposed for the specific processing. For example, among the pixels that are in a predetermined condition from the surroundings, the graphic pixel, the boundary point, the end point, or the isolated point is met. For example, there is a method of sequentially deleting pixels under the condition that the connectivity of the pixels is maintained or only one side is deleted if the line segment width is 2. Since thinning is a relatively well-known process, further detailed description of the processing content is omitted.
An example of the center line obtained by thinning is shown in the figure. It is explanatory drawing shown from a U-shaped building frame. Line segments L1 to L3 to be obtained are obtained. The end points of the line segments are called nodes N1 to N4.

For the obtained center line, the CPU models the connection state of the center lines (step S21). There are a wide variety of building frame shapes (see FIG. 5). If the texture DB 18 is prepared by classifying all of these cases, the load for creating the texture DB 18 and the data capacity thereof will be enormous. . Therefore, in this embodiment, the building shape is further simplified by modeling the connection ordinary of the center line. An example of modeling is shown in the figure.
First, when two line segments are connected, if the angle between them is θ> 90 + T (degrees), that is, if the obtuse angle is a predetermined value or more, these two line segments are regarded as “straight lines”. As shown in the figure, the line segments L11 and L12 are treated as a series of straight lines. As shown in the figure, even if the building shape is slightly curved in the middle, the state of the texture attached to the wall surface is considered to be the same as when these line segments are completely straight. Because.
Even when two line segments are connected, if the angle θ between them is within the range of 90 ± TH, it is treated as bending. As shown in the figure, the line segments L21 and L22 are treated as bent because the angle θ between them is within such a range.
Further, as shown in the figure, when three line segments are connected, if the angle between the central line segment L32 and the other line segment L31 is within the range of 90 ± TH, the branching occurs. And handle.
An angle TH used for dividing a straight line, a bend, and a branch can be arbitrarily set. Since it is a value used to simplify the case classification of texture selection patterns, the value of TH may be set based on the influence of the angle formed between the center lines on the exterior of the building.
When the modeling is completed, the CPU specifies the center line group having the longest length (step S22). For two or more line segments regarded as straight lines by modeling, a length is calculated by considering a series of line segment groups as one straight line, not a single line segment. As shown in the drawing, when the line segments L41, L42, and L43 are obtained, the line segments L41 and L43 are regarded as straight lines, and as a result, the longest part is a line segment group of “L41 + L42”.
When the centerline modeling and the longest line are obtained in this way, the texture DB 18 can be referred to based on this. Depending on the shape of the center line, necessary parameters such as the length of the “bent (branch) portion” may be calculated.

Based on the obtained center line shape, the CPU refers to the texture DB 18 and determines the texture of each surface (step S30).
Then, the number of texture arrays is calculated (step S31). This is because in the present embodiment, the texture DB 18 stores an image of a texture such as “window” as a minimum unit constituting the side surface. The method for calculating the number of sequences is illustrated in the figure. Consider the case where the texture of the reference size shown at the bottom is pasted on the side wall polygon. The number of repetitions in the height direction is determined based on the floor number of the building. In the example shown in the figure, the number of repetitions is set to 3 because it has three stories. Since the length in the height direction of the wall polygon does not necessarily match three times the height of the texture of the reference size, the texture is pasted after being enlarged or reduced in the height direction. A graphics engine such as OpenGL used to display a three-dimensional model by attaching a texture has such a function, and therefore it is not necessary to adjust the reference size when setting the texture.
The number of repetitions in the width direction of the wall polygon is obtained by rounding off “wall polygon width W / reference size texture width Wx”. In the example shown in the figure, the number of repetitions is calculated as “4” by rounding off “wall polygon width W / reference size texture width Wx”. At the time of display, the texture of the reference size is expanded to the width Wx1, so that it is pasted on the wall polygon exactly four times. Such an extended function can also be realized by the graphics engine.

When the CPU forms a three-dimensional polygon of the building by the above processing and determines the texture and the number of arrays for each side, the CPU stores the information as a three-dimensional model in the three-dimensional map DB 17 (step S32).
Then, the above processing is repeated while sequentially selecting buildings to be processed, and when the processing for all buildings is completed (step S33), the three-dimensional map data generation processing is terminated.

F. Effects and variations:
FIG. 13 is an explanatory diagram illustrating an example of generating a three-dimensional model. The upper part of FIG. 13 shows an example of a school building. A window texture is pasted on a rectangular three-dimensional polygon in the longitudinal direction, that is, on a plane parallel to the center line. The wall texture is affixed to the intersection. An example of a housing estate is shown in the middle of FIG. The center line has an E-shape having a branch, and is classified into a type in which the length of the bent (branch) portion is short. The veranda texture is pasted on the longitudinal direction of the longest part, that is, the plane parallel to the center line, and the wall texture is pasted on the intersecting plane. If texture DB18 (refer FIG. 8) is utilized, textures, such as a staircase, can be affixed on the bending | flexion (branch) part which hits the back of a figure.
The lower part of FIG. 13 shows an example of a three-dimensional map in which these three-dimensional models are arranged. It can be seen that a 3D map without any sense of incongruity is realized although it is an automatically generated 3D model.

According to the three-dimensional map data generation system of the present embodiment described above, the center line obtained by thinning the building frame is used, and the shape is taken into consideration for buildings of various planar shapes. You can use different textures. Therefore, a three-dimensional model with improved reality can be generated with a light processing load.
The various features described in this embodiment are not necessarily all provided, and the present invention may be configured by omitting or combining some of these features. The present invention is not limited to the above-described embodiments, and various modifications such as the following examples can be configured.
(1) Regarding the proper use of texture, in addition to the proper use based on the center line shape of the building frame, various conditions may be considered. For example, the side facing the road can be treated as the front regardless of the centerline shape, or the surface with a very short distance from the adjacent building can be treated as a wall regardless of the centerline shape. Good. In a residential building such as an apartment, the side facing the south side may be treated as a window regardless of the shape of the center line.
(2) The texture may be used by switching in the height direction of the building. For example, a texture for the first floor that represents the entrance / exit, a texture for the top floor that represents the edge of the rooftop portion, and the like may be prepared, and these may be used in combination with the texture shown in FIGS.
(3) In the embodiment, an example is shown in which a texture is set for an automatically generated three-dimensional polygon. However, the present invention also applies to a case where a texture is automatically set for a three-dimensional polygon generated by an operator. Is available.

  The present invention can be used to generate three-dimensional map data including a three-dimensional model representing a three-dimensional shape of a building.

DESCRIPTION OF SYMBOLS 10 ... 3D map data generation system 11 ... Command input part 12 ... Processing object specific | specification part 13 ... 3D polygon generation part 14 ... Building frame shape analysis part 15 ... Texture setting part 16 ... 2D map DB
17 ... 3D map DB
18 ... Texture DB

Claims (8)

A 3D map data generation system for generating 3D map data including a 3D model representing a 3D shape of a building,
A texture database storing a plurality of types of textures to be pasted on the side of the three-dimensional model;
A building frame shape analysis unit that obtains a centerline by thinning a building frame that is a planar shape of the building;
A three-dimensional map data generation system comprising: a texture setting unit that sets a texture to be attached to the side surface from the texture database based on a positional relationship between the center line and the side surface of the three-dimensional model of the building. The three-dimensional map data generation system according to claim 1,
The texture setting unit is a three-dimensional map data generation system that switches a selection pattern for selecting the texture based on at least one of the shape of the center line and the length of each line segment constituting the center line. The three-dimensional map data generation system according to claim 1 or 2,
The three-dimensional model is attached with type information indicating the type of the building,
The texture setting unit is a three-dimensional map data generation system that switches a selection pattern for selecting the texture according to the type of the building. A three-dimensional map data generation system according to any one of claims 1 to 3,
The building frame shape analysis unit groups the line segment group as a straight line when the interior angle formed by the line segment constituting the center line is an obtuse angle of a predetermined value or more,
The texture setting unit is a three-dimensional map data generation system that sets the texture based on the grouping. A three-dimensional map data generation system according to any one of claims 1 to 4,
The texture setting unit is a three-dimensional map data generation system that sets an opening texture representing an opening for a side surface substantially parallel to the center line. A three-dimensional map data generation system according to any one of claims 1 to 5,
A three-dimensional map data generation system including a three-dimensional model generation unit that generates the three-dimensional model based on the building frame as preprocessing for setting the texture. A 3D map data generation method for generating 3D map data including a 3D model representing a 3D shape of a building by a computer,
As steps executed by the computer,
Referring to a texture database storing a plurality of types of textures to be pasted on the side of the three-dimensional model;
Thinning a building frame that is a planar shape of the building to obtain a center line;
A method of generating three-dimensional map data, comprising: setting a texture to be attached to the side surface from the texture database based on a positional relationship between the center line and the side surface of the three-dimensional model of the building. A computer program for generating three-dimensional map data including a three-dimensional model representing a three-dimensional shape of a building by a computer,
A function of referring to a texture database storing a plurality of types of textures to be pasted on the side surface of the three-dimensional model;
A function of obtaining a center line by thinning a building frame that is a planar shape of the building;
A computer program for realizing, by a computer, a function of setting a texture to be attached to the side surface from the texture database based on a positional relationship between the center line and the side surface of the three-dimensional model of the building.