JPH06149943A - Device and method for preparing object data from perspective drawing - Google Patents

Abstract

PURPOSE:To easily and speedily prepare the object data of a three-dimensional object in any arbitrary shape by projecting a cross-sectional line onto a plane with a visual point as the center and acquiring the object data from the projected image. CONSTITUTION:As a perspective drawing, a drawing displaying the cross-sectional line at the time of cutting the three-dimensional object with the plane is used. Then, an input part 11 inputs the perspective drawing, the position data of erased points on the perspective drawing and an instruction from the outside and calculates the position data of the visual point. Next, a plane expression calculation part 12 calculates an equation inside the three-dimensional space of the plane corresponding to the cross- sectional line by utilizing the position data of the viewpoint and the position data of erased points. Further, a projection calculation part 13 calculates the projected image by projecting the cross-sectional line onto the plane (inside the three-dimensional space) expressed by the calculated equation and acquired the position data or coordinate data of the cross-sectional line from the calculated projected image. Then, the result provided by the projection calculation part 13 is outputted by an output part 14 as the object data of the three-dimensional object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for creating object data from a perspective view showing a three-dimensional object of an arbitrary shape, and more particularly to a single image on which a three-dimensional object is projected or drawn. The present invention relates to an apparatus and method for creating object data of an original three-dimensional object using a computer from a photograph, an electronic image, a sketch, a picture, a perspective drawing (perspective) of a building, and the like.

[0002]

2. Description of the Related Art It is often desired to obtain object data of an original three-dimensional object (coordinates of each point forming the three-dimensional object) from a perspective view obtained by projecting a three-dimensional object on a two-dimensional plane. For example, there is a case where a three-dimensional object model is created based on a sketch or perspective drawn by the industrial designer for designing the appearance of a product. In such a case, since the three-dimensional object itself is in the middle of design and does not yet exist in the actual three-dimensional space, the original three-dimensional object cannot be directly measured to obtain the object data. .

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

As a method for obtaining the object data of the original three-dimensional object from one object drawn by a two-point or three-point perspective view, there is a method disclosed in Japanese Patent Laid-Open No. 154972/1993. Since this method determines the vanishing point from the straight line bundle connecting the symmetric points and obtains the symmetry plane from the symmetric points to determine the three-dimensional coordinates, it can be applied only to a bilaterally 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 obtaining computer input data for CAD processing from a sketch drawn on the designer, actually create a mockup model with paper or viscosity according to the sketch,
Object data is obtained by actually measuring the created mockup. These operations are very labor intensive.

An object of the present invention is to provide a device and method for creating object data from a perspective view that can easily and quickly create object data of a three-dimensional object having an arbitrary shape drawn in only one perspective view. is there.

[0007]

An object data creating apparatus for a perspective view of the present invention creates 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. A perspective view in which a cross-sectional line when the three-dimensional object is cut along a plane is drawn in the projection image, position data of a vanishing point corresponding to the plane, and the perspective view. Inputting means for inputting position data of the viewpoint, and plane formula calculating means for obtaining an equation expressing the plane in the 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 the plane represented by the equation calculated by the plane expression calculation means and acquiring the object data from the coordinates of the calculated projection image.

A method of creating object data from a perspective view of the present invention is a method of creating object data of the three-dimensional object from one perspective view on which a projected image of a three-dimensional object having an arbitrary shape is displayed. The perspective view is used from the positional relationship between the vanishing point corresponding to the plane and the viewpoint of the perspective view, using the perspective view in which the cross-sectional line when the three-dimensional object is cut on the plane is drawn in the projection image. A first step of obtaining an equation expressing the plane in a three-dimensional space including the object data, and the object data from the image projected by projecting the sectional line with the viewpoint as the projection center on the plane represented by the equation. And a second step of acquiring.

[0009]

In a three-dimensional space (real space), a straight line (segment) perpendicular to one plane is generally projected on a perspective view as
All converge to the same vanishing point. When this plane and the perspective view are both arranged in a three-dimensional space, the normal vector of this plane and the vector from the vanishing point corresponding to this plane to 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 the equation in the three-dimensional space of the 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 plane section line is added to the projection image of the three-dimensional object on the perspective view. As described above, since the plane in the three-dimensional space corresponding to this cross section line is obtained, if the cross section line on the perspective view is projected onto the plane in this three-dimensional space with the viewpoint as the projection center, When the three-dimensional object is arranged in the three-dimensional space, the line coincides with the section line. Since the plane equation in the three-dimensional space is also known, it means that the coordinate data in the three-dimensional space for the cross-section line is obtained. Needless to say, the cross-sectional line constitutes a part of the three-dimensional object, and thus the object data of this three-dimensional object is obtained by the above. Although there is one parameter left in the equation of the plane, this parameter only determines the scaling factor, and does not cause distortion in the projection on the plane.

Further, the present invention is particularly effective when there are a plurality of sectional lines and these sectional lines intersect each other. In such a case, first, the first cross-section line is projected into the three-dimensional space as described above (at this time, the equation of the plane is displayed by one parameter). Then, the same processing is performed for the second cross section line, but 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 it is described by the parameter of the plane corresponding to the section line of, the intersection point also belongs to the plane corresponding to the second section line. Therefore, the parameter of the plane corresponding to the second section line is set to the first parameter. It can be described by the parameter corresponding to the cross section line, and the positional relationship between the first and second cross section lines can be obtained correctly in the three-dimensional space.

When there are many cross-section lines, the above 2
By repeating the process of connecting two cross-section lines, the relative positional relationship between all cross-section lines can be obtained correctly in the three-dimensional space, and the object data of all cross-section lines at this time correspond to the first cross-section line. It will be described by only one parameter (similarity ratio). If there are many cross-section lines, it is considered that the original three-dimensional object is expressed to a satisfactory degree by these cross-section lines.
Apart from the scaling factor, correct and substantially complete object data will be obtained for a three-dimensional object.

[0013]

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

This object data creating device creates object data of this three-dimensional object from a perspective view in which the three-dimensional object is displayed. As the perspective view, one in which a cross-sectional line when a three-dimensional object is cut by a plane is displayed is used. The object data creation apparatus includes an input unit 11 for calculating viewpoint position data by inputting a perspective view, position data of vanishing points on the perspective view, and an instruction from the outside, and position data of viewpoints and vanishing points. A plane equation calculation unit 12 that calculates an equation in a three-dimensional space of a plane corresponding to the sectional line using the position data, projects the sectional line on the 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 the cross-section line from the calculated projection image, and an output unit that outputs the result obtained by the projection calculation unit 13 as object data of a three-dimensional object. 14 and.

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 of the present invention.

First, a two-dimensional perspective view is input to the input unit 11 (step 101). Next, if necessary, image processing such as a differential filter is performed on the perspective view (step 102), and a line segment is extracted from the perspective view (step 103). The reason why the line segment is extracted here is to handle the projected image of the three-dimensional object and the cross-sectional line as a set of line segments.

Next, the position data of the vanishing point 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 for the position of the vanishing point. The vanishing point is, of course, in the plane containing the perspective. Subsequently, the input unit 11 calculates the position of the viewpoint of the perspective view (step 105). Of course, the position of the viewpoint may be input from the outside, but it is difficult to intuitively determine the position of the viewpoint from the perspective view unlike the vanishing point. It is desirable to find the position. Then, each position data or perspective view input to the input unit 11 or calculated by the input unit 11 is sent to the plane-type calculation unit 12.

For each vanishing point, the plane equation calculating unit 12 calculates an equation in the three-dimensional space of the plane corresponding to the vanishing point (step 106). Here, the calculation procedure of this plane equation will be described in detail. Here, as shown in FIG.
It is assumed that the perspective view 20 in which 1 is projected is input. Here, as the coordinates of the three-dimensional space, consider a coordinate system in which the XY plane coincides with the perspective view 20 and the viewpoint F is represented by (0,0, f). Each ridge of the cube 21 is a section line because it can be regarded as a cut of each face (a plane) of the cube.
The 12 edges of the cube are parallel to each other, and when projected on the perspective view 20, the left vanishing point LV (lv _x ,
lv _y , 0), right vanishing point RV (rv _x , rv _y , 0), and medium vanishing point MV (mv _x , mv _y , 0) as vanishing lines. Here, the planes of the cube corresponding to the vanishing points LV, RV, and MV are the left vertical plane P _L , the right vertical plane P _R , and the horizontal plane P _{H, respectively.}
And Also, seeing from the viewpoint F, the perspective view 20 and the cube 21
A plane that is on the other side of and is parallel to the perspective view 20 is referred to as a front plane P _F. The normal vectors of the left and right vertical planes P _L and P _R point toward the left vanishing point and the right vanishing point, respectively. The normal vector of the horizontal plane P _H is directed toward the middle vanishing point. The normal to the front plane P _F is parallel to the line of sight.

FIG. 4 is a side view of the three-dimensional space in which the perspective view 20 and the cube 21 are arranged as described above, and FIG. 5 is a view from directly above (these views are based on the orthogonal projection method). Drawn). As is clear from these figures, the normal vector of the horizontal plane P _H and the vector (−mv _x , −mv _y , f) directed from the middle vanishing point MV to the viewpoint are parallel. Therefore, if the horizontal plane P _H is expressed by an equation in a three-dimensional space,

[0020]

[Equation 1] Becomes

The normal vector of the left vertical plane P _L and the vector (-lv _x , -lv _y , f) directed from the left vanishing point LV to the viewpoint are parallel. 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 the front plane P _F is perpendicular to the viewpoint, the equation of the front plane _F is

[0024]

[Equation 4] Becomes Here, d is a parameter. As described above, the equation of each plane is calculated, and the equation thus calculated is sent to the projection calculation unit 13.

Next, the plane and the section line are associated with each other. Since a plurality of cross-section lines are generally drawn in the image of the three-dimensional object projected on the perspective view, how the individual cross-section lines and the plane correspond to the projection calculation unit 13 via the input unit 11. It is instructed and input whether or not (step 107). It should be noted that it may be automatically determined which of the left, right, horizontal, and front planes the input section line corresponds to.
In this case, since the corresponding vanishing points are the same for a plurality of cross-section lines formed by a plurality of mutually parallel planes,
It is possible to correspond the same plane to each section line,
In reality, each section line in the three-dimensional space corresponds to one of mutually parallel planes that differ only in the parameter d. Since the parameter d has not yet been determined here, it is assumed to correspond to the same plane.

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

Next, each sectional line is projected onto the corresponding plane in the three-dimensional space with the viewpoint F as the projection center (step 1).
08). As mentioned above, the perspective view is X in coordinates in three-dimensional space.
It is set to coincide with the Y plane. Here, FIG.
A case where projection is performed using the perspective view 30 in which the hat-shaped object of (B) is drawn will be described with reference to FIG. 7.

First, the horizontal sectional line L _H1 on the perspective view 30 is set to 3
_Project onto a 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 planes parallel to each other. 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 section line L _H1 on the perspective view 30,
At any position of the extension of this vector, the point b ₁ (x ₀ , y ₀ ,
z ₀ ), and this point b ₁ is included in the horizontal plane P _H1 . Then, by substituting b ₁ into equation (1),

[0029]

[Equation 5] As described above, the value of the parameter d is determined. As a result, the horizontal plane P _H1 is fixed in the three-dimensional space (FIG. 7 (A)).

Next, with the viewpoint F as the center of projection, the points a ₂ , a ₃ and 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 and b ₄ is obtained (FIG. 7 (B)). The coordinate point _{a 2 (a x, a y} , 0), which the corresponding point b a _second coordinate (b _x, b _y, b _z) When, the vector directed from the point of view F to point a ₂ ( a _x , a _y , −f), the vector from the viewpoint F to the point b ₂ is n times that.

[0031]

[Equation 6] Is established. Substituting equations (5) and (6) into equation (1) and solving for n,

[0032]

[Equation 7] Becomes By substituting the obtained n into the equation (6), the coordinates of the point b ₂ can be obtained. Similarly, the points b ₃ and b ₄ are obtained.

Incidentally, in the perspective view 30, the point a ₁ on the horizontal section line L _H1 is also the 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 the formula (4), the front plane P
The equation of _F1 is

[0034]

[Equation 8] Becomes The points a ₅ , a ₆ , a ₇ on the front sectional line are projected on the front plane P _F1 to obtain the projected points b ₅ , b ₆ , b ₇ (FIG. 7 (C)). Using the parameter n as above,

[0035]

[Equation 9] Since n is determined by the above, points b ₅ , b ₆ and 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). In the above processing, since the projection is performed with respect to the points on the cross-section line (for example, the points a _{1 to} a _{7 in} the above case), the line connecting the projected points is obtained by this interpolation. Further, in the case of a cross-section line drawn by freehand, the obtained object data may be distorted, so 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 the wire frame model, the object data is converted into the surface model based on the chamfering process.

By the above processing, it is possible to create the object data for the three-dimensional object drawn on one perspective view.

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

[0040]

[Equation 10] And when the projection plane is the right vertical plane, the equation corresponding to equation (7) is

[0041]

[Equation 11] Is.

Next, an example in which the object data is actually obtained based on the perspective view drawn by the designer will be described. FIG. 8 is a sketch of a compact camera drawn by the designer in perspective projection. 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 drawn. It is not difficult for industrial designers and architects to draw cross-section lines in such a freehand state.

Then, the processing from step 101 to step 109 in the flowchart of FIG. 2 was executed to calculate the object data of each cross section line in the three-dimensional space. Once the object data is obtained for the cross-section line, the figure represented by the object data can be freely rotated or similarly 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 cross-section line in the middle is that, for example, the cross-section line of that part is not drawn in the sketch because it is behind the lens part. The result obtained by performing the chamfering process in step 110 is shown in FIG.
Is shown in. As is clear from this figure, sufficiently satisfactory three-dimensional object data was created from one sketch, and modeling of the three-dimensional object was possible.

The embodiment of the present invention has been described above.
In the present invention, the number of vanishing points can be selected arbitrarily as one or more. The planes are 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 orientation can be freely used. 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, the positional relationship between the cross-section lines in the three-dimensional space can be correctly obtained. It is possible.

[0045]

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

[Brief description of drawings]

FIG. 1 is a block diagram showing 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 device of FIG.

FIG. 3 is a diagram showing an arrangement of vanishing points and planes in a perspective view of a cube.

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

5 is a view of the space including the perspective view and the cube of FIG. 3 as seen from above.

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

7A to 7C are diagrams 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 the perspective view of a compact camera.

9 is a front view of the 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. 10 is a perspective view of the 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 the 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 Part 12 Plane Calculation Part 13 Projection Calculation Part 14 Output Part 20,30 Perspective View 21 Cube 101-110 Step F Viewpoint L _F Front Section Line L _H Horizontal Section Line L _L Left Vertical Section Line L _R Right Vertical Section Line P _F Front plane P _H Horizontal plane P _L Left vertical plane P _R Right vertical plane LV Left vanishing point MV Middle vanishing point RV Right vanishing point

Claims (4)

[Claims] 1. An object data creating device for creating object data of a three-dimensional object from a perspective view of a projected image of a three-dimensional object having an arbitrary shape, wherein the three-dimensional object is cut in a plane. A perspective view in which the cross-section line when drawn is in the projection image, position data of vanishing points corresponding to the plane, and input means for inputting position data of viewpoints of the perspective views, and of the vanishing points Plane equation calculating means for obtaining an equation expressing the plane in the three-dimensional space including the perspective view from the position data and the position data of the viewpoint; and the plane equation on the plane represented by the equation obtained by the plane equation calculating means. An apparatus for creating object data from a perspective view, which comprises a projection calculation means for calculating a projection image of a cross-section line and acquiring the object data from the coordinates of the calculated projection image. 2. 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 a three-dimensional object is orthographically projected. The object data creation device according to claim 1, which is as described above. 3. A method of creating object data of a three-dimensional object from a perspective view showing a projected image of a three-dimensional object of an arbitrary shape, the method comprising: The perspective view in which the cross-section line is drawn in the projection image is used, and the plane is expressed in the three-dimensional space including the perspective view from the positional relationship between the vanishing point corresponding to the plane and the viewpoint of the perspective view. And a second step of obtaining the object data from the projected image by projecting the cross-section line with the viewpoint as the projection center on the plane represented by the equation. Method for creating object data from the. 4. The object data creating method according to claim 3, wherein at least two cross-section lines sharing an intersection with each other are used in a perspective view, and a plane corresponding to one of the cross-section lines is used. The first and second steps are carried out with respect to the one section line, and subsequently, the intersection point in the projected image in the second step is formed on the plane corresponding to the other section line. A method of creating object data from a perspective view, wherein the first and second steps are performed on a plane corresponding to the other section line and the other section line as a reference position in a three-dimensional space.