JP2011232798A - Graphic processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a graphic processor which controls an occurrence of operation error in a graphic Boolean operation and can accurately extract a shape of polygon constituting visible parts of object in the three-dimensional shape.SOLUTION: When a shielding determination processing unit 6 determines that a surface of polygon is not shielded by a contour shape, a polygon shape output unit 7 outputs a shape of the polygon, and when the shielding determination processing unit 6 determines that the surface of polygon is partially shielded by the contour shape, the polygon shape output unit 7 generates a polygon excluding a surface shielded by the contour shape upon implementing a graphic Boolean operation between the surface of the polygon and the contour shape, and outputs a shape of the polygon.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a graphic processing apparatus that extracts the shape of a polygon that constitutes a visible portion of an object when a three-dimensional object composed of a plurality of polygons is viewed from a viewpoint in a three-dimensional space. Is.

In a general graphic processing apparatus that draws a three-dimensional object composed of a plurality of polygons, the three-dimensional object is viewed from a viewpoint in the three-dimensional space (for example, a position specified by the user). In some cases, a function of performing a process of extracting the shape of a polygon constituting the visible portion of the object is provided.
In such polygon shape extraction processing, for example, when the polygons constituting the three-dimensional object are polygon A and polygon B, it is necessary to determine the shielding relationship between polygon A and polygon B.

When a three-dimensional object is viewed from the viewpoint, if polygon A is completely occluded by polygon B, polygon B is the only polygon that makes up the visible part of the object, and polygon A does not correspond. .
On the other hand, when the polygon B is completely shielded by the polygon A, the polygon that constitutes the visible portion of the object is only the polygon A, and the polygon B does not correspond.

When a part of the polygon A is shielded by the polygon B when the object having a three-dimensional shape is viewed from the viewpoint, it is necessary to calculate the shape of the polygon A that is not shielded by the polygon B.
On the other hand, when a part of the polygon B is shielded by the polygon A, it is necessary to calculate the shape of the polygon B which is not shielded by the polygon A.
For example, figure boolean operation (polygon A-polygon B) or the like can be used to calculate the shape of the polygon A that is not shielded by the polygon B.

Here, the case where the three-dimensional object is composed of polygons A and B has been shown, but when the three-dimensional object is composed of N polygons, the shielding relationship between the polygons is determined. If the processing is performed N × (N−1) times and it is found that a part is shielded, it is necessary to perform a graphic boolean calculation to calculate the shape of the polygon that is not shielded.
Hereinafter, a specific example of processing for calculating the shape of a part of a polygon that is not shielded by another polygon when a part of the polygon is shielded by another polygon will be described.

FIG. 10 is an explanatory diagram showing the extraction process of the polygon A that is partially blocked by the polygons C1, C2, C3, and C4.
In this case, the graphic Boolean calculation is performed between the polygon A and the polygon C1, and the graphic Boolean calculation is performed between the calculation result (the polygon A that is not shielded by the polygon C1) and the polygon C2.
Further, a graphic boolean calculation is performed between the calculation result (polygon A of the portion not shielded by the polygons C1 and C2) and the polygon C3, and the calculation result (polygon of the portion not shielded by the polygons C1, C2, and C3). A graphic boolean operation is performed between A) and the polygon C4.
Thereby, the polygon A of the part which is not shielded by the polygons C1, C2, C3 and C4 is generated.
In this way, the calculation result of the previous graphic Boolean calculation is used for the next graphic Boolean calculation.

In the course of this calculation, polygon and polygon figure boolean operations may be performed, resulting in the generation of extremely small or extremely elongated polygons (polygons that are not shielded by other polygons).
At this time, when a figure Boolean calculation is performed between a very small shape or an extremely long and narrow polygon and another polygon, a polygon having a correct shape may not be generated due to a calculation error.
For example, polygon vertex data is often expressed in floating-point numbers, but information may be generated when a small polygon or extremely long and thin polygon (for example, when the distance between the vertexes of the polygon is very small) is subject to graphic boolean operations. An error such as a drop may occur, and the geometric state may collapse.

Specifically, for example, as shown in FIG. 11, when a very elongated triangle B is shielded by a triangle A, two parts surrounded by a dotted circle are represented by a graphic Boolean operation (triangle B−triangle A). ).
However, in the triangle C composed of vertex 1, vertex 2 and vertex 3, when the positions of vertex 1 and vertex 2 are very close, the calculation of the process of calculating vertex 1 and vertex 2 is a floating point operation. Error occurs. For example, in Ax + By, an error occurs when the values of A and B are large and x and y are very small values.

If this calculation error results in a calculation result in which the positions of the vertex 1 and the vertex 2 of the triangle C are reversed, the shape of the triangle C collapses.
In this case, the shape in which vertex 1, vertex 2 and vertex 3 are originally counterclockwise becomes a clockwise shape due to a calculation error.
Due to such a phenomenon, the relation between the front and back of the polygon and the inside / outside determination of the polygon are mistaken.

  The following Patent Document 1 discloses a technique for extracting a contour shape of a three-dimensional shape object by deleting a side shared by a plurality of polygons. The technology to suppress is not disclosed.

JP-A-6-266819 (paragraph numbers [0006] to [0011], FIG. 1)

  Since the conventional graphic processing apparatus is configured as described above, when a graphic Boolean operation is repeatedly performed for each polygon constituting a three-dimensional shape object, a small polygon or When an extremely long and narrow polygon is generated and the polygon becomes the target of the next figure boolean operation, a calculation error occurs, and the shape of the polygon constituting the visible portion of the three-dimensional object is accurately extracted. There was a problem that made it impossible.

  The present invention has been made to solve the above-described problems, and suppresses the occurrence of calculation errors in figure Boolean operations, so that the shapes of polygons constituting the visible portion of a three-dimensional object can be accurately determined. It is an object of the present invention to obtain a graphic processing apparatus that can be extracted.

  When the graphics processing apparatus according to the present invention sees a three-dimensional object composed of a plurality of polygons from a viewpoint in a three-dimensional space, one or more polygons constituting the surface of the object are displayed. A surface polygon extracting means for extracting, a projection converting means for projecting and converting one or more polygons extracted by the surface polygon extracting means on a two-dimensional plane; The contour shape extracting means for extracting the continuous surface as the contour shape of the object among the surfaces of the object that the polygons constitute, and the surface of the polygon is contoured for each polygon extracted by the surface polygon extracting means. A shielding determination means for determining whether or not the contour shape extracted by the shape extraction means is shielded, and a polygon shape output means, When the occluding determination means determines that the polygon surface is not shielded by the contour shape, the polygon shape is output, and the shielding determining means determines that a part of the polygon surface is shielded by the contour shape. In such a case, by performing a graphic boolean operation between the surface of the polygon and the contour shape, a polygon from which the surface shielded by the contour shape is removed is generated and the shape of the polygon is output. It is a thing.

  According to the present invention, when a three-dimensional object composed of a plurality of polygons is viewed from a viewpoint in a three-dimensional space, a surface from which one or more polygons constituting the surface of the object are extracted. A polygon extraction unit, a projection conversion unit that projects and converts one or more polygons extracted by the surface polygon extraction unit onto a two-dimensional plane, and one or more polygons that are projected and converted onto a two-dimensional plane by the projection conversion unit A contour shape extracting means for extracting a continuous surface as the contour shape of the object, and a surface of the polygon for each polygon extracted by the surface polygon extracting means. And a shielding determining means for determining whether or not the contour shape extracted by the polygon is output by the polygon shape output means. When it is determined that the polygon surface is not shielded by the contour shape, the polygon shape is output, and when it is determined by the shielding determination means that a part of the polygon surface is shielded by the contour shape, Since the figure Boolean operation is performed between the polygon surface and the contour shape, a polygon from which the surface shielded by the contour shape is removed is generated, and the polygon shape is output. There is an effect that it is possible to accurately extract the shape of the polygon constituting the visible portion of the three-dimensional shape object while suppressing the occurrence of calculation errors in the graphic boolean calculation.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the figure processing apparatus by Embodiment 1 of this invention. It is a block diagram which shows the computer which comprises the graphics processing apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the graphics processing apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows an example of the object of the three-dimensional shape comprised by the some polygon. It is explanatory drawing which shows the example by which the polygon was projected and converted on the two-dimensional plane by carrying out parallel projection conversion of the polygon. It is explanatory drawing which shows the shape of the polygon output from the polygon shape output part 7. FIG. It is explanatory drawing which shows the example of extraction of the outline shape of an object. It is a block diagram which shows the figure processing apparatus by Embodiment 3 of this invention. It is explanatory drawing which shows the example of extraction of the outline shape of an object. It is explanatory drawing which shows the extraction process of the polygon A in which one part is shielded by polygon C1, C2, C3, C4. It is explanatory drawing which shows an example of the triangle calculated | required by figure Boolean calculation.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a graphic processing apparatus according to Embodiment 1 of the present invention.
In FIG. 1, a viewpoint accepting unit 1 is composed of a man-machine interface such as a keyboard and a mouse, for example, and accepts the position of the viewpoint in a three-dimensional space for viewing a three-dimensional object composed of a plurality of polygons. Perform the process.
The data storage unit 2 is a memory that stores data of a plurality of polygons constituting an object having a three-dimensional shape.

The surface polygon extraction unit 3 extracts one or more polygons constituting the surface of the object when a three-dimensional object is viewed from the viewpoint in the three-dimensional space where the position is received by the viewpoint reception unit 1 Perform the process. The surface polygon extraction unit 3 constitutes surface polygon extraction means.
The projection conversion processing unit 4 performs a process of projecting and converting one or more polygons extracted by the surface polygon extraction unit 3 onto a two-dimensional plane. Note that the projection conversion processing unit 4 constitutes a projection conversion means.

The contour shape extraction unit 5 extracts a continuous surface as the contour shape of the object among the surfaces of the objects formed by one or more polygons projected and converted onto a two-dimensional plane by the projection conversion processing unit 4. Perform the process. Note that the contour shape extraction unit 5 constitutes a contour shape extraction means.
For each polygon extracted by the surface polygon extraction unit 3, the shielding determination processing unit 6 performs a process for determining whether or not the surface of the polygon is shielded by the contour shape extracted by the contour shape extraction unit 5. The shielding determination processing unit 6 constitutes a shielding determination unit.

  When the shielding determination processing unit 6 determines that the polygon surface is not blocked by the contour shape, the polygon shape output unit 7 outputs the polygon shape, and the shielding determination processing unit 6 outputs a part of the polygon surface. If it is determined that the shape is occluded by the contour shape, a polygon is calculated between the surface of the polygon and the contour shape to generate a polygon that excludes the surface shielded by the contour shape. Then, a process for outputting the shape of the polygon is performed. The polygon shape output unit 7 constitutes a polygon shape output means.

  In the example of FIG. 1, a viewpoint receiving unit 1, a data storage unit 2, a surface polygon extraction unit 3, a projection conversion processing unit 4, a contour shape extraction unit 5, an occlusion determination processing unit 6, and a polygon shape, which are components of the graphic processing device. Although each of the output units 7 is assumed to be configured with dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted or a one-chip microcomputer), the graphic processing device is configured with a computer. When processing, the processing contents of the viewpoint receiving unit 1, the data storage unit 2, the surface polygon extraction unit 3, the projection conversion processing unit 4, the contour shape extraction unit 5, the occlusion determination processing unit 6 and the polygon shape output unit 7 are described. May be stored in the memory of a computer, and the CPU of the computer may execute the program stored in the memory.

2 is a block diagram showing a computer constituting the graphic processing apparatus according to Embodiment 1 of the present invention.
In FIG. 2, an application memory 11 is a recording medium such as a RAM or a hard disk built in the computer, and includes a viewpoint receiving unit 1, a data storage unit 2, a surface polygon extraction unit 3, a projection conversion, which are components of the graphic processing apparatus. An application which is a program describing the processing contents of the processing unit 4, the contour shape extraction unit 5, the shielding determination processing unit 6, and the polygon shape output unit 7 is stored.
The system memory 12 is a recording medium such as a RAM or a hard disk that holds instruction codes executed by the arithmetic processor 13 and data of a plurality of polygons constituting a three-dimensional object.

The arithmetic processor 13 is composed of a CPU, for example, and executes an application stored in the application memory 11 while referring to an instruction code held in the system memory 12.
Note that an OS or the like is mounted on the arithmetic processor 13, and an application or task stored in the application memory 11 operates on the OS to configure a portion where the three-dimensional shape object can be seen. A process for accurately extracting only polygons is performed.
FIG. 3 is a flowchart showing the processing contents of the graphic processing apparatus according to Embodiment 1 of the present invention.

Next, the operation will be described.
Here, for convenience of explanation, an object having a three-dimensional shape composed of a plurality of polygons is represented by vertices A, B, C, D, E, F, G, H, I, J, It is assumed that the object A has K.
This three-dimensional object has a cross section in the XZ plane as shown in FIG.
The Y axis of this three-dimensional object is in the depth direction of FIG. 4. If the position of the circle in FIG. 4 is the viewpoint, when the three-dimensional object is viewed from that viewpoint, the thick line in FIG. The surface represented is visible and the surface represented by the thin line is invisible.

The viewpoint receiving unit 1 receives the position of the viewpoint for viewing the three-dimensional object, and outputs position information indicating the position of the viewpoint to the surface polygon extraction unit 3.
When the surface polygon extraction unit 3 receives the position information from the viewpoint reception unit 1, the surface polygon extraction unit 3 acquires data of a plurality of polygons constituting the three-dimensional shape object stored in the data storage unit 2.
The surface polygon extraction unit 3 extracts one or more polygons constituting the surface of the object when the object of the three-dimensional shape is viewed from the viewpoint position indicated by the position information output from the viewpoint reception unit 1 (Step ST1).

The following method can be used as a method for extracting the polygon constituting the surface.
When the normal of the polygonal surface is defined (for example, when the normal vector is in the direction parallel to the Z-axis starting from the X-axis), the normal vector does not collide with other surfaces. If the surface is the surface of a 3D shape object and hits another surface, then the surface hit by the normal vector is determined to be the back surface of the 3D shape object, the surface of the 3D shape object is Constructing polygons can be extracted.
On the other hand, when the normal of the polygonal surface is not defined, the surface of the 3D-shaped object is the surface in consideration of the relationship between the top and bottom of the vertex order determined when the 3D-shaped object is formed If it is determined whether or not, the polygons constituting the surface of the three-dimensional object can be extracted.

In the example of FIG. 4, the surface of the polygon between vertex F-vertex G, vertex H-vertex I, vertex J-vertex K, vertex K-vertex A is determined to be the back surface of the three-dimensional object, and is deleted. The surface of the polygon between the other vertices is extracted as the surface of the three-dimensional object.
That is, the surface of the polygon between vertex A-vertex B-vertex C-vertex D-vertex E-vertex F, vertex G-vertex H, vertex I-vertex J is extracted as the surface of the three-dimensional object.

When the surface polygon extraction unit 3 extracts one or more polygons constituting the surface of the object having a three-dimensional shape, the projection conversion processing unit 4 projects and converts these polygons onto a two-dimensional plane (step ST2).
As a method of projecting and converting a polygon onto a two-dimensional plane, generally, a method of performing parallel projection conversion of a polygon, a method of performing perspective projection conversion of a polygon, or the like can be considered.
In the case of parallel projection conversion of a polygon, an operation of truncating the depth information of the polygon data is performed. For example, when viewing the Z-axis direction from the viewpoint shown in FIG. 4, if the projection is on a plane perpendicular to the Z-axis, information on the Z coordinate is discarded.
On the other hand, when performing perspective projection conversion of a polygon, the polygon can be converted by dividing the X coordinate and Y coordinate of the polygon by the Z coordinate.

Here, FIG. 5 is an explanatory diagram showing an example in which a polygon is projected and converted onto a two-dimensional plane by performing parallel projection conversion on the polygon.
When polygons are subjected to parallel projection conversion, the depth information of the polygon data is lost, but in the example of FIG. 5, they are virtually arranged in the depth order.

When the projection conversion processing unit 4 projects and converts one or more polygons onto a two-dimensional plane, the contour shape extraction unit 5 converts the continuous surfaces of the objects formed by those polygons to the object's surface. Extract as a contour shape (step ST3).
For example, if one or more polygon surfaces projected and converted by the projection conversion processing unit 4 are polygon surfaces between the vertex A, the vertex B, the vertex C, the vertex D, the vertex E, and the vertex F, first, By examining the polygon of vertex A-vertex B and the polygon of vertex B-vertex C, which is an adjacent polygon sharing the side of the position of vertex B, the surface consisting of vertex A-vertex B-vertex C is Recognize that the surface is continuous.
Next, by checking the polygon of vertex B-vertex C and the polygon of vertex C-vertex D, which is an adjacent polygon sharing the side of the position of vertex C, vertex A-vertex B-vertex C-vertex The surface consisting of D is recognized as a continuous surface.
Next, by examining the polygon of vertex C-vertex D and the polygon of vertex D-vertex E, which is an adjacent polygon sharing the side of the position of vertex D, vertex A-vertex B-vertex C-vertex The surface formed by D-vertex E is recognized as a continuous surface.
Finally, by examining the polygon of vertex D-vertex E and the polygon of vertex E-vertex F, which is an adjacent polygon sharing the side of the position of vertex E, vertex A-vertex B-vertex C-vertex The surface formed by D-vertex E-vertex F is recognized as a continuous surface.
Thereby, in the example of FIG. 5, the surface which consists of the vertex A-vertex B-vertex C-vertex D-vertex E-vertex F is extracted as outline shape (1).

  If the polygon plane projected and converted by the projection conversion processing unit 4 is a polygon plane between the vertex G and the vertex H, the side of the vertex H is shared with the polygon of the vertex G and the vertex H. There is no polygon that is the surface of the three-dimensional object (the vertex H-vertex I polygon shares the side at the position of the vertex H, but is excluded because it is the back surface of the three-dimensional object) Further, since there is no polygon which is the surface of the object of the three-dimensional shape sharing the side of the position of the vertex G with the polygon of the vertex G-vertex H (the polygon of the vertex F-vertex G is the position of the vertex G In the example of FIG. 5, the surface composed of the vertex G and the vertex H is extracted as the contour shape (2).

  If the polygon plane projected and converted by the projection conversion processing unit 4 is a polygon plane between the vertex I and the vertex J, the polygon at the vertex I and the vertex I share the side of the vertex I. There is no polygon that is the surface of the object (the polygon of vertex H-vertex I shares the edge at the position of vertex I, but is excluded because it is the back side of the object), and the vertex I-vertex J Since there is no polygon that is the surface of the object sharing the side of the position of the vertex J with the polygon (the vertex K-the polygon of the vertex J shares the side of the position of the vertex J, In the example of FIG. 5, the surface composed of vertex I-vertex J is extracted as the contour shape (3).

When the contour shape extraction unit 5 extracts the contour shapes (1), (2), and (3) of the object, the occlusion determination processing unit 6 extracts the surface of the polygon and the contour shape for each polygon extracted by the surface polygon extraction unit 3. The shielding relationship between the contour shapes (1), (2), and (3) extracted by the extraction unit 5 is verified (step ST4).
The shielding determination processing unit 6 verifies the shielding relationship between the polygon surface and the contour shapes (1), (2), and (3), so that a part of the polygon surface is the contour shape (1) (2) ( 3) or whether the polygon surface is not shielded by the contour shapes (1), (2), and (3) (or the polygon surfaces are contour shapes (1), (2), and (3)). It is determined whether the surfaces of the polygons are completely shielded by the contour shapes (1), (2), and (3) (steps ST5 and ST6).

Specifically, first, the occlusion determination processing unit 6 includes the surface of the polygon of vertex A-vertex B and the contour shape (1) among the polygons constituting the surface of the object. The shielding relationship between them is verified (step ST4).
Since the vertex A-vertex B polygon surface and the contour shape (1) are the same surface, it is determined that the vertex A-vertex B polygon surface is not shielded by the contour shape (1) (steps ST5, ST6). ) The verification target of the shielding relationship is changed to the contour shape (2) (steps ST8 and ST9).

Thereby, the shielding determination processing unit 6 verifies the shielding relationship between the surface of the polygon of vertex A-vertex B and the contour shape (2) (step ST4).
Since the contour shape (2) exists on the far side of the polygonal surface of vertex A-vertex B, it is determined that the polygonal surface of vertex A-vertex B is not shielded by the contour shape (2) ( In steps ST5 and ST6), the verification target of the shielding relationship is changed to the contour shape (3) (steps ST8 and ST9).
Thereby, the shielding determination processing unit 6 verifies the shielding relationship between the polygonal surface of vertex A-vertex B and the contour shape (3) (step ST4).
Since the contour shape (3) exists on the far side of the polygonal surface of vertex A-vertex B, it is determined that the polygonal surface of vertex A-vertex B is not shielded by the contour shape (3). (Steps ST5 and ST6).

In the example of FIG. 5, at this stage, all the contour shapes have been subjected to the shielding relation verification target (steps ST8 and ST9), and thus the shielding relation verification processing for the polygonal surfaces of vertex A-vertex B is completed. .
As described above, since the shielding determination processing unit 6 determines that the polygonal surfaces of the vertex A and the vertex B are not shielded by the contour shapes (1), (2), and (3), the polygon shape output unit 7 Then, the polygon shape of vertex A-vertex B is output (step ST10).

Next, the occlusion determination processing unit 6 selects the surface of the vertex B-vertex C polygon as the occlusion relation verification target among the polygons constituting the surface of the object (steps ST11 and ST12). -The shielding relation between the polygonal surface of the vertex C and the contour shape (1) is verified (step ST4).
Since the polygonal surface of vertex B-vertex C and the contour shape (1) are the same surface, it is determined that the polygonal surface of vertex B-vertex C is not shielded by the contour shape (1) (steps ST5, ST6). ) The verification target of the shielding relationship is changed to the contour shape (2) (steps ST8 and ST9).

Thereby, the shielding determination processing unit 6 verifies the shielding relationship between the polygonal surface of vertex B-vertex C and the contour shape (2) (step ST4).
Since the contour shape (2) exists on the back side of the polygonal surface of vertex B-vertex C, it is determined that the polygonal surface of vertex B-vertex C is not shielded by the contour shape (2) ( In steps ST5 and ST6), the verification target of the shielding relationship is changed to the contour shape (3) (steps ST8 and ST9).
Thereby, the shielding determination processing unit 6 verifies the shielding relationship between the polygonal surface of vertex B-vertex C and the contour shape (3) (step ST4).
Since the contour shape (3) exists behind the polygonal surface of vertex B-vertex C, it is determined that the polygonal surface of vertex B-vertex C is not shielded by the contour shape (3). (Steps ST5 and ST6).

In the example of FIG. 5, at this stage, all the contour shapes are targeted for the shielding relation verification (steps ST8 and ST9), and thus the shielding relation verification processing for the polygonal surfaces of vertex B-vertex C is completed. .
As described above, since it is determined by the shielding determination processing unit 6 that the polygonal surface of the vertex B-vertex C is not shielded by the contour shapes (1), (2), and (3), the polygon shape output unit 7 , The polygonal shape of vertex B-vertex C is output (step ST10).

Among the polygons constituting the surface of the three-dimensional shape object, the vertex A-vertex D polygon surface, the vertex D-vertex E polygon surface, and the vertex E-vertex F polygon surface also apply to the vertex A. Verification is performed in the same manner as the polygonal surface of vertex B and the polygonal surface of vertex B-vertex C.
It is determined that the polygonal surface of vertex C-vertex D, the surface of vertex D-polygon of vertex E, and the surface of polygon of vertex E-vertex E are not shielded by the contour shapes (1), (2), and (3). Thus, the polygon shape output unit 7 outputs the shape of the vertex C-vertex D polygon, the shape of the vertex D-vertex E polygon, and the shape of the vertex E-vertex F polygon (step ST10).

Next, the shielding determination processing unit 6 selects the polygonal surface of the vertex G-vertex H among the polygons constituting the surface of the three-dimensional shape object as a shielding relation verification target (steps ST11 and ST12). The shielding relationship between the polygonal surface of vertex G-vertex H and the contour shape (1) is verified (step ST4).
The contour shape (1) exists on the near side of the polygonal surface of the vertex G-vertex H, and it is determined that a part of the polygonal surface of the vertex G-vertex H is shielded by the contour shape (1). (Step ST5).

When the shielding determination processing unit 6 determines that a part of the polygonal surface of the vertex G-vertex H is shielded by the contour shape (1), the polygon shape output unit 7 By performing a graphic boolean operation between the surface and the contour shape (1), a polygon from which the surface shielded by the contour shape (1) is removed is generated (step ST7).
That is, the polygon shape output unit 7 performs a difference calculation between the polygonal surface of the vertex G-vertex H and the contour shape (1) as a graphic boolean operation, thereby creating a new vertex as shown in FIG. GH is calculated and a polygon of vertex GH−vertex H is generated.
An existing Boolean calculation method can be applied as the calculation method of the figure Boolean calculation. For example, a library called “General Polygon Clipper (GPC)” can be used.

After generating the polygon of vertex GH-vertex H, polygon shape output unit 7 outputs the shape of the polygon (step ST10).
However, in the end, since a three-dimensional object is generated from the vertex GH−vertex H polygon, it is necessary to calculate the depth information of the newly calculated vertex GH.
Since the newly calculated vertex GH exists on the vertex G-vertex H polygon, the polygon shape output unit 7 uses the plane equation in the three-dimensional space of the vertex G-vertex H polygon to Depth information in the three-dimensional space in the GH is calculated and restored to data in the three-dimensional space.

When the shielding determination processing unit 6 verifies the shielding relationship between the polygonal surface of the vertex G-vertex H and the contour shape (1) as described above, the shielding relationship verification target is the contour shape (2). (Steps ST8 and ST9), and the shielding relation is verified between the polygonal surface of vertex G-vertex H and the contour shape (2).
At this time, the contour shape (2) shields a part of the polygonal surface of the vertex G-vertex H, but the polygonal surface of the vertex GH-vertex H is not shielded by the contour shape (2). Therefore, the graphic boolean calculation by the polygon shape output unit 7 is not performed.

In addition, the shielding determination processing unit 6 changes the shielding relationship verification target to the contour shape (3) (steps ST8 and ST9) and shields between the polygonal surface of the vertex G-vertex H and the contour shape (3). Verify the relationship.
At this time, since the contour shape (3) is the same surface as the polygonal surface of the vertex G-vertex H, the figure Boolean calculation by the polygon shape output unit 7 is not performed.
Therefore, when the surface of the polygon of vertex G-vertex H is the object to be verified for the shielding relationship, the polygon shape output from the polygon shape output unit 7 is only the shape of the polygon of vertex GH-vertex H.

Next, the shielding determination processing unit 6 selects the polygonal surface of vertex I-vertex J among the polygons constituting the surface of the three-dimensional shape object as a shielding relation verification target (steps ST11 and ST12). The shielding relation between the polygonal surface of vertex I-vertex J and the contour shape (1) is verified (step ST4).
The contour shape (1) exists on the near side of the polygon surface of vertex I-vertex J, and it is determined that a part of the polygon surface of vertex I-vertex J is shielded by the contour shape (1). (Step ST5).

When the shielding determination processing unit 6 determines that a part of the polygonal surface of the vertex I-vertex J is shielded by the contour shape (1), the polygon shape output unit 7 By performing a graphic boolean operation between the surface and the contour shape (1), a polygon from which the surface shielded by the contour shape (1) is removed is generated (step ST7).
That is, the polygon shape output unit 7 performs a difference operation between the polygonal surface of the vertex I-vertex J and the contour shape (1) as a graphic boolean operation, thereby creating a new vertex as shown in FIG. IJ is calculated and a polygon of vertex I-vertex IJ is generated.

After generating the polygon of vertex I-vertex IJ, polygon shape output unit 7 outputs the shape of the polygon (step ST10).
However, finally, since a three-dimensional object is generated from the polygon of vertex I-vertex IJ, it is necessary to calculate the depth information of the newly calculated vertex IJ.
Since the newly calculated vertex IJ exists on the polygon of vertex I-vertex J, the polygon shape output unit 7 uses the plane equation in the three-dimensional space of the polygon of vertex I-vertex J to The depth information in the three-dimensional space in IJ is calculated and restored to the data in the three-dimensional space.

When the shielding determination processing unit 6 verifies the shielding relationship between the polygonal surface of vertex I-vertex J and the contour shape (1) as described above, the shielding relationship verification target is the contour shape (2). (Steps ST8 and ST9), and the shielding relationship is verified between the polygonal surface of vertex I-vertex J and the contour shape (2).
At this time, since the contour shape (2) is the same surface as the polygonal surface of vertex I-vertex J, the graphic Boolean calculation by the polygon shape output unit 7 is not performed.

In addition, the shielding determination processing unit 6 changes the shielding relationship verification target to the contour shape (3) (steps ST8 and ST9), and shields between the polygonal surface of vertex I-vertex J and the contour shape (3). Verify the relationship.
At this time, the contour shape (3) exists on the back side of the polygon surface of vertex I-vertex J and does not shield the polygon surface of vertex I-vertex J. No figure boolean operation is performed.
Therefore, when the surface of the polygon of vertex I-vertex J is the object to be verified for the shielding relationship, the polygon shape output from the polygon shape output unit 7 is only the shape of the polygon of vertex I-vertex IJ.

As a result, the polygon shape output from the polygon shape output unit 7 is as follows, and the series of processing ends (step ST12).
Vertex shape of vertex A-vertex B
↓
Vertex B-Vertex C polygon shape
↓
Vertex C-Polygon D shape
↓
Vertex D-Vertex E polygon shape
↓
Polygon shape of vertex E-vertex F
↓
Vertex GH-Polygon shape of vertex H
↓
Vertex I-Polygon shape of vertex IJ

  As is apparent from the above, according to the first embodiment, when an object having a three-dimensional shape composed of a plurality of polygons is viewed from a viewpoint in the three-dimensional space, the surface of the object is formed. A surface polygon extraction unit 3 that extracts one or more polygons, a projection conversion processing unit 4 that projects and converts one or more polygons extracted by the surface polygon extraction unit 3 on a two-dimensional plane, and a projection conversion processing unit 4 A contour shape extraction unit 5 for extracting a continuous surface as the contour shape of the object among the surfaces of the object formed by one or more polygons projected and converted onto the two-dimensional plane by the surface polygon extraction unit A shielding determination processing unit 6 for determining whether or not the surface of the polygon is shielded by the contour shape extracted by the contour shape extraction unit 5 for each polygon extracted by 3; If the polygon shape output unit 7 determines that the polygon surface is not blocked by the contour shape by the shielding determination processing unit 6, the polygon shape output unit 7 outputs the polygon shape, and the shielding determination processing unit 6 outputs the polygon surface. When it is determined that a part is shielded by the contour shape, a polygon with the surface shielded by the contour shape is removed by performing figure boolean operation between the surface of the polygon and the contour shape. Generated and configured to output the shape of the polygon, suppresses the occurrence of calculation errors in figure Boolean operations, and accurately extracts the shape of the polygon that makes up the visible part of the three-dimensional object The effect which can be done is produced.

  In other words, according to the first embodiment, the object to be shielded is not the polygon surface × polygon surface, but the polygon surface × contour shape. If it is determined that the image is not occluded, there is no need to perform a graphic boolean operation. For this reason, the number of times that the graphic Boolean calculation is performed can be significantly reduced, so that the occurrence of calculation error in the graphic Boolean calculation is suppressed, and the shape of the polygon that forms the visible portion of the three-dimensional object can be reduced. It can be extracted accurately.

Embodiment 2. FIG.
In the first embodiment, the contour shape extracting unit 5 extracts the continuous surface as the contour shape of the object among the surfaces of the objects formed by one or more polygons. If there is a polygon that shares an edge with another polygon among one or more polygons that are projected and converted onto a two-dimensional plane by the projection conversion processor 4, the extraction unit 5 deletes the edge. The contour shape of the object may be extracted by repeating it sequentially.
Specifically, it is as follows.

FIG. 7 is an explanatory diagram showing an example of extracting the contour shape of an object.
When the projection conversion processing unit 4 projects and converts one or more polygons onto a two-dimensional plane, the contour shape extraction unit 5 selects other polygons and sides from the one or more polygons projected and converted onto the two-dimensional plane. A shared polygon is searched, a side shared by two polygons is deleted, and a new polygon is generated.
In the example of FIG. 7, the polygon (1) and the polygon (2) share one side, the side shared by the polygon (1) and the polygon (2) is deleted, and a new polygon (12 ) Is generated.

When the contour shape extraction unit 5 generates a new polygon, it further searches for a polygon that shares a side with another polygon, deletes a side shared by the two polygons, and generates a new polygon. To do.
The process of generating a new polygon is repeated until there is no side shared by the two polygons.
When there is no side shared by the two polygons, the remaining polygon outline shape becomes the object outline shape.

Embodiment 3 FIG.
8 is a block diagram showing a graphic processing apparatus according to Embodiment 3 of the present invention. In the figure, the same reference numerals as those in FIG.
When a three-dimensional object is covered with a closed loop, the contour shape extraction unit 8 searches for a side shared by the front surface and the back surface of the object, and among the sides shared by the front surface and the back surface, The process which extracts the edge | side couple | bonded by (5) as an outline shape is implemented. Note that the contour shape extraction unit 8 constitutes a contour shape extraction means.

  In the example of FIG. 8, each of the viewpoint receiving unit 1, the data storage unit 2, the surface polygon extraction unit 3, the occlusion determination processing unit 6, the polygon shape output unit 7, and the contour shape extraction unit 8 which are components of the graphic processing device. It is assumed that it is configured with dedicated hardware (for example, a semiconductor integrated circuit on which a CPU is mounted, or a one-chip microcomputer). A program describing the processing contents of the unit 1, the data storage unit 2, the surface polygon extraction unit 3, the occlusion determination processing unit 6, the polygon shape output unit 7 and the contour shape extraction unit 8 is stored in the memory of the computer. The CPU may execute a program stored in the memory.

Next, the operation will be described.
In the first embodiment, the contour shape extraction unit 5 has shown a case where a continuous surface is extracted as the contour shape of an object among the surfaces of objects formed by one or more polygons. When the shape object is covered with a closed loop, the contour shape extraction unit 8 searches for a side shared by the front surface and the back surface of the three-dimensional shape object, and among the sides shared by the front surface and the back surface. The sides connected at the vertices may be extracted as the contour shape.
Specifically, it is as follows.

FIG. 9 is an explanatory diagram showing an example of extracting the contour shape of an object.
FIG. 9 shows an example in which a three-dimensional object is a cube as a three-dimensional object covered with a closed loop.
When the 3D object is an object shape covered with a closed loop, all the surfaces of the 3D object are connected, and the outline shape of the 3D object becomes the boundary between the front surface and the back surface. .

In the example of FIG. 9, the polygon (1), the polygon (2), and the polygon (3) are the surfaces of a three-dimensional object.
On the other hand, polygon (4) (polygon on the opposite side of polygon (2)), polygon (5) (polygon on the opposite side of polygon (3)) and polygon (6) (polygon on the opposite side of polygon (1)) This is the back surface of the three-dimensional object.

First, the contour shape extraction unit 8 selects the polygon (1), polygon (3), polygon (5), and polygon (6) sharing the sides of the polygon (4) that is the back surface of the three-dimensional object. A search is performed to determine a polygon that is the surface of a three-dimensional object among the polygon (1), the polygon (3), the polygon (5), and the polygon (6). In this case, polygon (1) and polygon (3) are the surfaces of the object.
When the contour shape extraction unit 8 determines that the polygon (1) and the polygon (3) are the surfaces of an object having a three-dimensional shape, the side (1) shared by the polygon (4) and the polygon (1) is three-dimensional. It is recognized as a side forming the contour shape of the object having a shape.
Further, the side (2) shared by the polygon (4) and the polygon (3) is recognized as the side forming the contour shape of the three-dimensional object.

Next, the contour shape extraction unit 8 has the polygon (5), which is the back surface of the three-dimensional object, sharing the sides with the polygon (1), the polygon (2), the polygon (4), and the polygon (6). And polygons that are the surfaces of the three-dimensional object among the polygon (1), polygon (2), polygon (4), and polygon (6) are determined. In this case, polygon (1) and polygon (2) are the surfaces of the object.
When the contour shape extraction unit 8 determines that the polygon (1) and the polygon (2) are the surfaces of an object having a three-dimensional shape, the side (3) shared by the polygon (5) and the polygon (1) is three-dimensional. It is recognized as a side forming the contour shape of the object having a shape.
Further, the side (4) shared by the polygon (5) and the polygon (2) is recognized as the side forming the contour shape of the three-dimensional object.

Next, the contour shape extraction unit 8 has the polygon (6) which is the back surface of the object having the three-dimensional shape sharing the sides with the polygon (2), the polygon (3), the polygon (4), and the polygon (5). To determine the polygon which is the surface of the object having a three-dimensional shape among the polygon (2), polygon (3), polygon (4) and polygon (5). In this case, polygon (2) and polygon (3) are the surfaces of the object.
When the contour shape extraction unit 8 determines that the polygon (2) and the polygon (3) are the surfaces of an object having a three-dimensional shape, the side (5) shared by the polygon (6) and the polygon (2) is three-dimensional. It is recognized as a side forming the contour shape of the object having a shape.
Further, the side (6) shared by the polygon (6) and the polygon (3) is recognized as the side forming the outline shape of the three-dimensional object.
As described above, the contour shape extraction unit 8 extracts the side (1), the side (2), the side (3), the side (4), the side (5), and the side (6) as the contour shape of the three-dimensional shape object. .

  DESCRIPTION OF SYMBOLS 1 Viewpoint reception part, 2 Data storage part, 3 Surface polygon extraction part (surface polygon extraction means), 4 Projection conversion process part (projection conversion means), 5, 8 Contour shape extraction part (contour shape extraction means), 6 Shielding determination Processing unit (shielding determination unit), 7 Polygon shape output unit (polygon shape output unit), 11 Application memory, 12 System memory, 13 Arithmetic processor.

Claims (3)

  A surface polygon extracting means for extracting one or more polygons constituting the surface of the object when a three-dimensional object composed of a plurality of polygons is viewed from a viewpoint in the three-dimensional space; Projection converting means for projecting and converting one or more polygons extracted by the surface polygon extracting means onto a two-dimensional plane, and an object comprising one or more polygons projected and converted onto the two-dimensional plane by the projection converting means For each polygon extracted by the surface polygon extraction means, the surface of the polygon is extracted by the contour shape extraction means. Shielding determining means for determining whether or not the extracted contour shape is shielded, and the polygonal surface is contoured by the shielding determining means. When it is determined that the polygon is not shielded by the shape, the polygon shape is output. When the shielding determination unit determines that a part of the polygon surface is shielded by the contour shape, A figure provided with polygon shape output means for generating a polygon from which the surface shielded by the outline shape is removed by performing figure boolean operation between the outline shapes and outputting the shape of the polygon Processing equipment.   The contour shape extraction unit performs processing for deleting the side when there is a polygon that shares a side with another polygon among one or more polygons projected and converted onto the two-dimensional plane by the projection conversion unit. The graphic processing apparatus according to claim 1, wherein the contour shape of the object is extracted by repeating sequentially.   A surface polygon extracting means for extracting one or more polygons constituting the surface of the object when a three-dimensional object composed of a plurality of polygons is viewed from a viewpoint in the three-dimensional space; When the object is covered with a closed loop, the side that the front and back sides of the object are shared is searched, and the side that is connected at the vertex among the sides that the front and back sides are shared is used as the outline shape. Contour shape extracting means for extracting, and shielding determination means for determining whether the surface of the polygon is shielded by the contour shape extracted by the contour shape extracting means for each polygon extracted by the surface polygon extracting means And when the shielding determining means determines that the polygon surface is not shielded by the contour shape, the polygon shape is output and the shielding determination is performed. When it is determined that a part of the polygonal surface is shielded by the contour shape by the step, a surface that is shielded by the contour shape by performing a graphic boolean operation between the polygonal surface and the contour shape And a polygon shape output means for generating a polygon from which the polygon is removed and outputting the shape of the polygon.

Images