JP3137776B2 - Object data creation device from perspective view - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for creating object data from a single perspective view displaying a three-dimensional object having an arbitrary shape, and more particularly, to an apparatus and method for projecting or drawing a three-dimensional object. about photos, electronic image, sketch, painting, complete prospective view of a building or the like (Perth), the equipment to create the object data for the three-dimensional object of the original using a computer.

[0002]

2. Description of the Related Art It is often desired to obtain object data of an original three-dimensional object (coordinates of respective points constituting the three-dimensional object) from a perspective view in which a three-dimensional object is projected on a two-dimensional plane. For example, there is a case where a model of a three-dimensional object is created based on sketches and perspectives drawn by an industrial designer for the appearance design of a product. In such a case, since the three-dimensional object itself is in the process of design and does not yet exist in the actual three-dimensional space, it is not possible to directly obtain the object data by directly measuring the original three-dimensional object. .

When there are two or more perspective views from different viewpoints, it is possible to analytically obtain object data based on the principle of binocular stereovision or surveying. When there is only one image, object data cannot be obtained by a method such as binocular stereovision.

[0004] As a method of obtaining object data of an original three-dimensional object from a single object drawn in a two-point or three-point perspective view, there is a method disclosed in Japanese Patent Application Laid-Open No. 3-154972. This method determines a vanishing point from a bundle of straight lines connecting the symmetric points and determines a three-dimensional coordinate by obtaining a symmetry plane from the symmetric point. Therefore, this method can be applied only to a left-right symmetric object.

[0005]

As described above, a method of obtaining object data of a three-dimensional object having an arbitrary shape from only one perspective view has not been found so far. Therefore, even when computer input data for CAD processing is obtained from a sketch drawn in the designer, a mockup model is actually created with paper or viscosity according to the sketch,
Actually, the created mockup is actually measured to obtain object data. These operations are very labor intensive.

An object of the present invention is to provide an object data generation equipment from the perspective view can be created easily and quickly the object data of a three-dimensional object having an arbitrary shape drawn on only one perspective .

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided an apparatus for creating object data from a perspective view, which creates object data of the three-dimensional object from a single perspective view on which a projected image of a three-dimensional object having an arbitrary shape is displayed. A perspective view in which a sectional line obtained by cutting the three-dimensional object in a plane is drawn in the projection image, position data of a vanishing point corresponding to the plane, and the perspective view. Input means for inputting position data of the viewpoint, and plane expression calculating means for obtaining an equation expressing the plane in a three-dimensional space including the perspective view from the position data of the vanishing point and the position data of the viewpoint, Projection calculation means for calculating a projection image of the cross-section line on a plane represented by the equation obtained by the plane expression calculation means, and acquiring the object data from the coordinates of the calculated projection image.

[0008]

[0009]

In a three-dimensional space (real space), a straight line (line segment) perpendicular to one plane is generally expressed as
All converge to the same vanishing point. When both the plane and the perspective view are arranged in the three-dimensional space, the normal vector of the plane and the vector from the vanishing point corresponding to the plane toward the viewpoint of the perspective view are parallel. Therefore, if the viewpoint and vanishing point of the perspective view are known, it is possible to obtain an equation in a three-dimensional space of a plane corresponding to the vanishing point (apart from the distance from the viewpoint to the plane). This equation is described with the distance from the viewpoint to the plane as the only parameter.

Here, it is assumed that a sectional line by a plane is added to a projected image of a three-dimensional object on a perspective view. As described above, a plane in the three-dimensional space corresponding to this cross-section line is obtained. Therefore, by projecting a cross-section line in a perspective view on a plane in this three-dimensional space with the viewpoint as the projection center, 3D object is arranged in a three-dimensional space. Since the equation of the plane in the three-dimensional space is also known, the coordinate data in the three-dimensional space for the section line has been obtained. Needless to say, the section line forms a part of the three-dimensional object, and thus the object data of the three-dimensional object is obtained. Although one parameter remains in the equation of the plane, this parameter only determines the similarity magnification and does not cause distortion in the projection on the plane.

Further, the present invention is particularly effective when the number of sectional lines is plural and these sectional lines cross each other. In such a case, first, the first section line is projected into the three-dimensional space as described above (at this time, the equation of the plane is represented by one parameter). Then, the same processing is performed for the second cross-section line. At this time, if the first and second cross-section lines share an intersection, the coordinates of this intersection in the three-dimensional space are the first. Since the intersection point also belongs to the plane corresponding to the second section line, the parameter of the plane corresponding to the second section line is changed to the first section parameter. The parameters can be described by the parameters corresponding to the section lines, and the positional relationship between the first and second section lines in the three-dimensional space can be correctly obtained.

When there are a large number of cross-section lines,
By repeatedly performing the process of connecting the two section lines, the relative positional relationship between all the section lines in the three-dimensional space is correctly obtained, and the object data of all the section lines at this time corresponds to the first section line. It is described with only one parameter (similarity magnification). If there are a large number of cross-section lines, it is considered that the original three-dimensional object is expressed to a degree that can be satisfied by these cross-section lines.
Apart from the similarity magnification, correct and substantially complete object data can be obtained for a three-dimensional object.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an object data creation device according to one embodiment of the present invention, and FIG. 2 is a flowchart for explaining the operation of this device.

This object data creating apparatus creates object data of a three-dimensional object from a perspective view in which the three-dimensional object is displayed. As the perspective view, a view in which a cross-sectional line obtained by cutting the three-dimensional object by a plane is used. The object data creating apparatus includes an input unit 11 that receives perspective data, a position data of a vanishing point on the perspective view, and an external instruction, and calculates position data of a viewpoint. A plane formula calculation unit 12 for calculating an equation in a three-dimensional space of a plane corresponding to the section line using the position data, and projecting the section line on a plane (in the three-dimensional space) represented by the obtained equation. A projection calculation unit 13 that calculates a projection image and obtains position data and coordinate data of a section line from the calculated projection image, and an output unit that outputs a result obtained by the projection calculation unit 13 as object data of a three-dimensional object. 14.

Next, the operation of this embodiment will be described with reference to FIG. The operation described here is based on the method for creating object data from a perspective view according to the present invention.

First, a perspective view drawn in two dimensions is input to the input unit 11 (step 101). Next, image processing such as a differential filter is performed on the perspective view as needed (step 102), and a line segment is extracted from the perspective view (step 103). Here, the line segment is extracted in order to handle the projection image and the cross-sectional line of the three-dimensional object as a set of line segments.

Next, the vanishing point position data is input to the input unit 11 (step 104). Depending on the contents of the perspective view, the vanishing line may be easily found, and the vanishing point as the convergence point of the vanishing line may be immediately known.
May have an automatic search function of the position of the vanishing point. Of course, the vanishing point lies in the plane containing the perspective view. Subsequently, the input unit 11 calculates the position of the viewpoint in the perspective view (Step 105). Of course, the position of the viewpoint may be input from the outside.However, unlike the vanishing point, it is difficult to intuitively determine the viewpoint position from the perspective view. It is desirable to determine the position. The position data and the perspective view input to the input unit 11 or calculated by the input unit 11 are sent to the plane type calculation unit 12.

The plane formula calculation unit 12 calculates, for each vanishing point, an equation in a three-dimensional space of a plane corresponding to the vanishing point (Step 106). Here, the calculation procedure of the equation of this plane will be described in detail. Here, as shown in FIG.
It is assumed that a perspective view 20 on which 1 is projected is input. Here, as a coordinate in the three-dimensional space, a coordinate system in which the XY plane matches the perspective view 20 and the viewpoint F is represented by (0, 0, f) is considered. Each ridge of the cube 21 is a cross-sectional line because it can be regarded as a cut of each surface (planar surface) of the cube.
The twelve ridges of the cube are parallel to each other by four, and when projected onto the perspective view 20, each of the left vanishing points LV (lv _x ,
lv _y, 0), the right vanishing point _{RV (rv x, rv y,} 0), converge as vanishing line in the middle vanishing point _{MV (mv x, mv y,} 0). Here, the planes of the cube corresponding to the vanishing points LV, RV, and MV are respectively referred to as a left vertical plane P _L , a right vertical plane P _R , and a horizontal plane P _H
And Also, seeing from the viewpoint F, the perspective view 20 and the cube 21
Of located on the other side, a front plan P _F a plane parallel with the perspective view 20. The normal vectors of the left and right vertical planes P _L and P _R are directed to the left vanishing point direction and the right vanishing point direction, respectively. The normal vector of the horizontal plane P _H points in the direction of the middle vanishing point. Normal of the front plane P _F is parallel to the line of sight.

FIG. 4 shows a three-dimensional space in which the perspective view 20 and the cube 21 are arranged as described above, and FIG. 5 shows a view from directly above (these figures are orthographic projections). Is drawn). As is clear from these figures, the normal vector of the horizontal plane P _H is parallel to the vector (−mv _x , −mv _y , f) from the middle vanishing point MV to the viewpoint. Therefore, when the horizontal plane P _H is represented by an equation in a three-dimensional space,

[0020]

(Equation 1) Becomes

[0021] is parallel to the vector towards the viewpoint from the normal vector and the left vanishing point LV left vertical plane _{P L (-lv x, -lv y} , f). Therefore, the equation of the left vertical plane P _L is

[0022]

(Equation 2) Similarly, the equation for the right vertical plane P _R is

[0023]

(Equation 3) Becomes Since front plan P _F is perpendicular to the viewpoint, the equation of the front plane _F,

[0024]

(Equation 4) Becomes Here, d is a parameter. As described above, the equations of each plane are calculated, and the calculated equations are sent to the projection calculation unit 13.

Next, the plane and the cross-section line are associated with each other. Generally, a plurality of cross-section lines are drawn in the image of the three-dimensional object projected on the perspective view, so how the individual cross-section lines correspond to the plane to the projection calculation unit 13 via the input unit 11. An instruction is given and input is made (step 107). Note that it may be automatically determined whether the input cross-section line corresponds to the left, right, horizontal, or front plane.
In this case, for a plurality of cross-sectional lines by a plurality of mutually parallel planes, the corresponding vanishing point is the same,
It is possible to make the same plane correspond to each section line,
In practice, in the three-dimensional space, each section line corresponds to one of mutually parallel planes differing only in the parameter d. Here, since the parameter d has not been determined yet, it is assumed that it corresponds to the same plane.

FIGS. 6A to 6C are examples showing which plane corresponds to a wedge-shaped, hat-shaped, and egg-shaped three-dimensional object with cross-sectional lines drawn. In the figure, for example, a cross section line with a horizontal cross section line L _H corresponds to a horizontal plane P _H , and a left vertical cross section line L _L , a right vertical cross section line L _R , and a front cross section line LF are respectively a left vertical cross section P _L and a right cross section line L _F vertical section P _R, which corresponds to the front section P _F.

Next, each sectional line is projected on a corresponding plane in a three-dimensional space with the viewpoint F as a projection center (step 1).
08). As described above, a perspective view is represented by X in coordinates in three-dimensional space.
It is set to match the Y plane. Here, FIG.
The case where projection is performed using a perspective view 30 in which a hat-shaped object is drawn in (B) will be described with reference to FIG.

First, the horizontal sectional line L _H1 on the perspective view 30 is set to 3
Projection is performed on the horizontal plane P _H1 in the dimensional space. at this point,
Since the equation of the horizontal plane P _H1 includes the parameter d, it is actually represented as a group of mutually parallel planes. Therefore, it is necessary to determine the horizontal plane P _H1 decide a point on the horizontal plane P _H1. Consider a vector from the viewpoint F to an arbitrary point a ₁ on the horizontal sectional line L _H1 on the perspective view 30,
The point b ₁ (x ₀ , y ₀ ,
z ₀ ) is set, and this point b ₁ is assumed to be included in the horizontal plane P _H1 . Then, by substituting b ₁ into equation (1),

[0029]

(Equation 5) Thus, the value of the parameter d is determined. Thus, the horizontal plane P _H1 is determined in the three-dimensional space (FIG. 7A).

Next, with the viewpoint F as the projection center, the points a ₂ , a ₃ , a ₄ on the horizontal section line L _H1 are projected onto the horizontal plane P _H1 , respectively, and the projected points b ₂ , b ₃ , b ₄ is obtained (FIG. 7 (B)). Assuming that the coordinates of the point a ₂ are (a _x , a _y , 0) and the coordinates of the corresponding point b ₂ are (b _x , b _y , b _z ), the vector from the viewpoint F to the point a ₂ is ( a _x , a _y , −f), the vector from the viewpoint F to the point b ₂ is n times as large, and

[0031]

(Equation 6) Holds. Substituting equations (5) and (6) into equation (1) and solving for n gives

[0032]

(Equation 7) Becomes When the the obtained n into equation (6), the coordinates of the point b ₂ are determined. Similarly, the points b ₃ and b ₄ are obtained.

By the way in perspective 30, point a ₁ on the horizontal section lines L _H1 is also a point on the front section line L _F1. Therefore, the front plane P _F1 in the three-dimensional space is the point b ₁ (x ₀ ,
y ₀ , z ₀ ). From this and equation (4), the front plane P
The equation for _F1 is

[0034]

(Equation 8) Becomes Projecting front section line point a _5, a _6, a ₇ to the front plane P _F1 respectively, to obtain a b _5, b _6, b ₇ points after projection (Fig. 7 (C)). If the parameter n is used as described above,

[0035]

(Equation 9) , The points b ₅ , b ₆ , b ₇ are obtained.

By the above operation, the point b ₁ in the three-dimensional space
Coordinates of ~b ₇ is that the Motoma' all.

Next, interpolation and correction processing is performed (step 109). Since the above processing is performed projecting the point of the cross-section line (e.g. a ₁ ~a ₇ points in the case described above) as a target, this interpolation, obtaining the line connecting the points of the projected. Also, in the case of a cross-section line drawn by freehand, the obtained object data may be distorted, so that appropriate correction is made. Then, a chamfering process is performed based on the object data thus obtained (step 110). Since the object data obtained from the cross-section line is basically based on a wire frame model, the object data is converted into data based on a surface model by chamfering.

By the above processing, object data for a three-dimensional object drawn on one perspective view has been created.

When the projection plane is a left vertical plane,
The equation corresponding to equation (7) is

[0040]

(Equation 10) When the projection plane is a right vertical plane, the equation corresponding to equation (7) is

[0041]

[Equation 11] It is.

Next, an example in which object data is actually obtained based on a perspective view drawn by a designer will be described. FIG. 8 is a sketch of a compact camera drawn by a designer in a perspective view. In this sketch, a plurality of left vertical section lines L _L , right vertical section lines L _R , and horizontal section lines L _H are respectively drawn. It is not difficult for industrial designers and architects to draw a sectional line in a state close to freehand.

Then, the processing of steps 101 to 109 in the flowchart of FIG. 2 was executed to calculate the object data of each section line in the three-dimensional space. If the object data is obtained for the section line, the graphic represented by the object data can be freely rotated or analogously deformed by CAD. FIG. 10 to FIG. 12 show the result of such rotation in the CAD. In these figures, the reason why there is a section line cut off in the middle is that the section line was not drawn in the sketch based on, for example, the shadow of the lens portion. Further, the result obtained by performing the chamfering process in step 110 is shown in FIG.
Is shown in As is apparent from this figure, sufficiently satisfactory object data of a three-dimensional object was created from one sketch, and modeling of the three-dimensional object could be performed.

The embodiments of the present invention have been described above.
In the present invention, one or more arbitrary points can be selected as the number of vanishing points. In addition, the plane is not limited to the left vertical plane, the right vertical plane, the front plane, and the horizontal plane, and any number of planes in any directions can be used freely. Further, when there are a plurality of cross-section lines and these cross-section lines do not intersect, if the distance between the cross-section lines is obtained by some method, it is possible to correctly obtain the positional relationship between the cross-section lines in the three-dimensional space. It is possible.

[0045]

As described above, according to the present invention, an equation in a three-dimensional space of a plane corresponding to a cross section line is obtained from a vanishing point and viewpoint position data using a perspective view in which the cross section line is drawn. By projecting the sectional line on the plane represented by this equation with the viewpoint as the projection center, the object data of a three-dimensional object of an arbitrary shape can be easily and quickly obtained from only one perspective view. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an object data creation device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of the apparatus of FIG.

FIG. 3 is a diagram showing an arrangement of each vanishing point and each plane in a perspective view of a cube.

FIG. 4 is a side view of a space including the perspective view and the cube of FIG. 3;

FIG. 5 is a top view of a space including the perspective view and the cube of FIG. 3;

FIGS. 6A to 6C are two-dimensional perspective views of a wedge-shaped object, a hat-shaped object, and an egg-shaped object, respectively.

FIGS. 7A to 7C are diagrams each showing a process of creating three-dimensional object data from a perspective view in which a hat-shaped object is drawn.

FIG. 8 is a sketch with a section line based on a perspective view of a compact camera.

FIG. 9 is a front view in which object data is acquired by the method of the present invention based on the sketch of FIG. 8 and CAD is created based on the acquired data.

FIG. 10 is a perspective view of object data acquired by the method of the present invention based on the sketch of FIG. 8 and created by CAD based on the acquired data.

FIG. 11 is a side view of object data acquired by the method of the present invention based on the sketch of FIG. 8 and created by CAD based on the acquired data.

FIG. 12 is a diagram showing an example in which object data is acquired by the method of the present invention based on the sketch of FIG. 8 and chamfering processing is performed based on the acquired data.

[Explanation of symbols]

11 input unit 12 plane expression calculation section 13 projection calculation unit 14 outputs 20 and 30 perspective views 21 cubic 101-110 Step F viewpoint L _F front sectional line L _H horizontal section line L _L Left vertical section line L _R right vertical section line P _F front plan P _H horizontal plane P _L left vertical plane P _R right vertical plane LV left vanishing point MV in vanishing point RV right vanishing point

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-154972 (JP, A) IPSJ IPSJ Graphics and CAD Symposium, pp. 43-52, Shusaku Furushima et al. “3D Sketch System” Development of IEICE Transactions, vol. J 72-DII, no. 4, 517-525, Toshie Tanaka, et al., "3D Shape Reconstruction of Polyhedron by Parallelism Hypothesis" Transactions of the Information Processing Society of Japan 29, pp. 686-693, Kunio Kondo et al. Application ”(58) Fields surveyed (Int. Cl. ⁷ , DB name) G06F 17/50 624 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. An object data creating apparatus for creating object data of a three-dimensional object from a single perspective view on which a projected image of a three-dimensional object having an arbitrary shape is displayed, wherein the three-dimensional object is cut by a plane. A perspective view in which a cross-sectional line when the projection image is drawn in the projected image, position data of a vanishing point corresponding to the plane, and input means for inputting position data of a viewpoint in the perspective view, Plane expression calculation means for obtaining an equation representing the plane in a three-dimensional space including the perspective view from the position data and the position data of the viewpoint; and Projection data calculating means for calculating a projected image of a section line and obtaining the object data from the coordinates of the calculated projected image. 2. The plane is one of a plane parallel to a front view, a plane parallel to a left side view, a plane parallel to a right side view, and a plane parallel to a plan view when orthographically projecting a three-dimensional object. 2. The object data creation device according to claim 1, wherein: