JPH03100885A - Three-dimensional graphic display device - Google Patents

Abstract

PURPOSE:To accelerate the display processing of a three-dimensional graphic by cutting data in the unrequired part of a graphic displayed on a plotting part at early stages by arranging a clipping part prior to a visual field conversion part. CONSTITUTION:The clipping part 3 of an image processing part 20 is equipped with a clipping boundary plane reverse conversion part 32 to perform the reverse conversion of each clipping boundary plane which forms the boundary of an area set in the coordinate system of a display plane to a fundamental coordinate system, and a cutting part 33 to cut the graphic when it protrudes from each reverse-converted clipping boundary plane, and also, it is arranged prior to the visual field conversion part 5. Thereby, a wasteful processing in a three- dimensional graphic display device which displays the three-dimensional graphic in CG or CAD, etc., can be eliminated, which attains the acceleration of the display processing.

Description

[Detailed Description of the Invention] (Summary) This invention relates to a three-dimensional figure display device, and in particular, to improving the processing speed of a three-dimensional figure display device that displays three-dimensional figures using CG, CAD, etc., by eliminating unnecessary processing and displaying. In order to achieve high-speed processing, there is a data storage section that stores the graphic data to be displayed on the display means based on the basic coordinate system, and a data storage section that stores the graphic data to be displayed on the display means. an image processing unit including a visual field conversion processing unit that converts a figure to be displayed on a display screen into a display surface coordinate system based on a virtual viewpoint and visual field data; and a clip unit that clips image data other than the image data to be displayed; A three-dimensional image display device comprising: a drawing section for displaying image data processed by the section on a display means;
The clip unit of the image processing unit includes a clip boundary plane inverse transformation unit that inversely transforms each clip boundary plane forming the boundary of the area set in the coordinate system of the display surface to the basic coordinate system;
The present invention includes a pruning section that cuts off any graphics that protrude from each of the inversely transformed clip boundary planes, and is arranged prior to the visual field conversion section.

(Industrial Application Field) The present invention relates to a three-dimensional graphic display device, and particularly to a CG (Com
Puter Graphics) and CAD (Comp
The present invention relates to an improvement in the processing speed of a three-dimensional figure display device that displays three-dimensional figures, such as by using ``Uter Aided Design''.

(Prior Art) When displaying a figure on a figure display device, since the display screen is limited, the portions that protrude from the display screen are cropped.

For this reason, in normal graphic display devices, a process called clipping is performed to generate a new graphic by cutting off a portion of the graphic outside of a certain area. By this clipping process, the figures a and s in FIG. 6(a) can be clipped according to the boundary C, and the figures a* and bt in FIG. 6(b) can be output.

Algorithms for clipping figures have already been developed for each target figure. The region to be clipped is generally a convex region whose boundaries are composed of planes, and usually a rectangular parallelepiped is used, each plane of which is perpendicular to the coordinate axis.

The configuration of a graphic display device commonly used in the past is described in the fifth section.
As shown in the figure, (ISO, “Information
processing systems-Com
puter graphics -Pro-gram
er”s Hierarchical Interact
ive Graphics System - (PHIG
According to this example, the graphic display device includes a data management unit IO, a modeling conversion unit 11, a color calculation unit 12, a visual field conversion unit 13, a clip unit 14, and a drawing unit 15. It consists of

Here, the data management section 10 is a section that stores and manages shape data of figures representing objects to be displayed, and boundary information for clipping processing is also managed here. Usually, objects are
Each component has its own modeling coordinate system (
MC) and refer to them during assembly.

The modeling conversion section 11 is a section that converts graphic data stored in the data management section 10 into a common world coordinate system (WC). Since each graphic data is defined by its own MC, each model uses its own modeling conversion matrix for converting to WC. Note that information on the light source and viewpoint for determining the color of the surface is also defined in this WC.

The color calculation unit 12 is a part that calculates the color of the figure converted into WC based on information about the light source and viewpoint.

The visual field conversion unit 13 converts the coordinates of the figure whose color has been calculated into a normalized projected coordinate system (which is a coordinate system parallel to the display surface) from the WC based on the virtual viewpoint or the data of the camera position and viewpoint. This is the part that converts to NPC).

The clip section 14 is a section that cuts off a portion that protrudes from a preset display area. Since the region is convex, clipping for the region is completed by sequentially performing clipping for each boundary plane.

The drawing unit 15 projects the clipped figure onto the display surface of a display means (not shown) and displays it.

In this manner, in conventionally commonly used graphic display devices, the data of figures stored and managed in the data management section 10 is converted from the modeling coordinate system to the world coordinate system in the modeling conversion section 11, and the figure data is converted from the modeling coordinate system to the world coordinate system. After the color calculation unit 12 calculates the color, the visual field conversion unit 13 converts the world coordinate system to the normalized projected coordinate system. Thereafter, the portion protruding from the display area is clipped by the clip section 14 and displayed on the display screen by the drawing section 15.

[Problem to be solved by the invention]

However, in such graphic display devices, all of the graphic data stored and managed in the data management section is subject to conversion and calculation processing up to the clipping section, and it is not necessary for display until it is harvested at the clipping section. Only parts will be processed. Therefore, processing such as color calculation and visual field conversion is also performed on the data that would be cropped in the clipping process, which causes an increase in processing time.

An object of the present invention is to eliminate the above-mentioned wasteful processing and achieve high-speed display processing.

(Means for Solving the Problems) Means for solving the above problems in the present invention are as shown in FIG. The data storage unit 21 that stores data based on the data storage unit 21
A visual field conversion processing unit 5 converts the graphic data stored in the display device into a display surface coordinate system based on the virtual viewpoint and visual field data of the graphic to be displayed on the display surface of the display means, and a clip that clips image data other than the image data to be displayed. In the three-dimensional image display device, the clipping section 3 of the image processing section has an image processing section 20 that includes an image processing section 3, and a drawing section 6 that displays the image data processed by the image processing section 20 on a display means. A clip boundary plane inverse transformation unit 32 that inversely transforms each clip boundary plane forming the boundary of an area set in the coordinate system to the basic coordinate system; and a pruning section 33 for reaping.1. This is because it is arranged prior to the visual field converting section 5 described above.

(Function) In the present invention, since the clipping section is arranged in advance of the visual field conversion section, data of unnecessary portions of the figure displayed in the drawing section can be clipped at an early stage.

Therefore, visual field conversion, which takes time to process, is performed only on the minimum necessary data, and three-dimensional figure display processing can be performed at high speed.

(Examples) Hereinafter, the present invention will be described in detail based on examples shown in the accompanying drawings.

FIG. 2 is a block diagram showing an embodiment of a three-dimensional graphic display device according to the present invention. In this embodiment, the data management section 11 excluding the clipping section 3, the modeling conversion section 2,
The color calculation section 4, visual field conversion section 5, and drawing section 6 are the same as those used in the conventional device, and a new lip section 3 is arranged between the modeling conversion section 2 and the color calculation section 4. There is.

Here, the data management section 1 and the modeling conversion section 2 function as a data storage section whose basic coordinate system is WC, and the clip section 3, color calculation section 4, and visual field conversion section 5 function as an image processing section.

The configuration of the clip section 3 described above is shown in FIG. 3.

This clip part 3 is 1. It consists of a command interpretation section 31, a clip boundary plane inverse transformation section 32, and a pruning section 33.

Here, the command interpreter 31 analyzes the command header attached to the beginning of the data flowing from the modeling converter 2, determines the type of data, and identifies those related to the clipping process. Data related to clipping processing include a visual field transformation matrix, clipping boundary values, and graphic data.

The clipping boundary plane inverse transformation unit 32 inversely transforms the WC into a clipping boundary plane WC defined as a boundary value in NPC. This inverse transformation can be performed as follows.

The conversion formula to coordinate coordinate transform the point P of WC to the point P' of NPC is: The formula to convert this to the plane of NPC is: PY', PZ', PW'l are homogeneous of P and p' Homogeneous Coordinate
The relationship between the expression 0 normal coordinate [px*pyspzl and homogeneous coordinates is px=PX/PW prPY/PW
pz=PZ/PW. (1)X
The same applies to spy 19Z'l. In a homogeneous coordinate system, there is a property that even if the term W is multiplied by any numerical value other than O, it corresponds to a point with the same normal coordinates.

Here, take the point [LLZ] and create the vector [a, b, c]
When the equation of the plane perpendicular to , ax+by+cz+dmO(2), is expressed using the point [x*y#Z#W] expressed in homogeneous coordinates, it becomes ax+by+cz+dwmO(3). If this plane is the plane of WC, then (4). (James F, B111nn, “A H
omogeneous Formula for
Lines in 3Space,”Compute
rGraphics, Vol. 11. No, 2.
pp, 237-241. (1977).

Reference) The equation of the plane after conversion is a” x” + b” y’ + d” w’ mO (5)
Rewriting equation (4), the plane of NPC is WC
The formula for inverse transformation to the plane of is (6).

Therefore, equation (6) can be used to inversely transform the plane forming the clip-wrapping boundary from NPC to WC.

That is, when the conditional expression for a certain boundary surface to be inside the clip area is a'x'+b'', e◆cIzI◆d''W°≧0, this can be expressed as [a'sb',C'', dol The clip boundary plane of the corresponding WC is ax+b
Let y+cz+dw≧0(7) be a conditional expression for the WC clip boundary plane.

Therefore, when one side of the clip boundary plane is X°≧xmin, this parameter is [a' * b' * c' * d' ] - [1eOm
O# −xmtnl (8), so the clipping plane of the corresponding WC can be calculated as (9).

The pruning unit 33 pruns the figure using the parameters of the clipping boundary plane converted to WC. This pruning can be performed as follows.

Normally, a clipping boundary is composed of a plane perpendicular to the coordinate axes, but the boundary surface converted back to WC using equation (9) is not necessarily perpendicular to the coordinate axes. Therefore, in the present invention, it is necessary to use clipping on an arbitrary plane. Clipping on this arbitrary plane is an extension of clipping on a plane perpendicular to the normal coordinate axes.

Normal clipping consists of (a) determining whether a point used to define the shape of a figure, such as a vertex of a polygon or an end point of a line, is inside or outside the area; (b) determining the intersection of a figure and a boundary surface; It consists of the desired parts.

For example, when clipping a line segment, (a) the part that determines whether or not the end points of the line are inside or outside the area; and (b) the part that determines the intersection point if the line segment intersects with the boundary, but in this case ( (b-1) Find the internal division ratio of the intersection on the line segment (b-2)
Calculate the coordinates of the intersection according to the ratio.

It can be separated into two parts. Since the part (b-2) does not depend on the direction of the boundary plane, the present invention is also the same as the conventional one. Therefore, (a) and (b-1) will be explained in more detail.

Regarding the inside/outside determination of the area regarding both endpoints Pi and P2 of the line segment in (a), use the calculation result of the conditional expression for the clip boundary plane in WC in (7) to calculate Dmax+by+cz
A discriminant expressed as +dw≧0 is calculated, and an inside/outside determination is made based on the sign or negative of the value of D.

Regarding the calculation of the internal division ratio of the intersection point pt on the line segment in (b-1), using the fact that the value of the discriminant calculated above is proportional to the distance from the boundary plane, 1 to snow 1 - The intersection ratio k can be calculated by 02. here,
DI and D2 are the values of the discriminant for the end points Pi and P2 of the line segment, respectively.

When the internal division ratio of the intersection point pt is obtained in this way, the coordinates p t (x, y, z) of the intersection point pt become Pt (x, y, z
) ■ (1-k) Pi (x, y, z) + kP2 (x, y,
z) can be calculated.

FIG. 4 shows the relationship between pt, Pi, and P2.

Although the above is a case of line segments, a similar method can be used for other figures such as polygons, and clipping of any plane can be realized.

Furthermore, for polygons, data other than coordinate values may be attached to each vertex, such as data related to color such as a normal vector. It can be calculated by linear interpolation from the internal division ratio.

Note that although clipping is performed in the WC in this embodiment, it is also possible to perform the clipping in a coordinate system different from the WC.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of the present invention, Fig. 2 is a block diagram showing an embodiment of the three-dimensional graphic display device according to the invention, Fig. 3 is a block diagram showing the specific configuration of the clip section, and Fig. 4 5 is an explanatory diagram showing the relationship between intersection points and end points, FIG. 5 is a block diagram showing the configuration of a conventional three-dimensional graphic display device, and FIGS. 6(a) and (b)
) is an explanatory diagram of clipping processing. [Effects of the Invention] As described above, according to the three-dimensional display device of the present invention, it is possible to perform clipping processing prior to color calculation and visual field conversion, so that it is possible to perform clipping processing prior to color calculation and visual field conversion. There is no need to perform processing such as color calculation or visual field conversion on the part. Therefore, the amount of processing can be reduced, and three-dimensional display can be performed at higher speed. 6...Drawing section 20...Image processing section 21...Data storage section 32...Clip boundary plane inverse transformation section 33...Pruning section

Claims (1)

[Claims] A data storage section (21) that stores graphic data to be displayed on a display means based on a basic coordinate system; A visual field conversion processing unit that converts the figure to the display surface coordinate system based on the virtual viewpoint and visual field data of the figure to be displayed on the display surface (
5) and a clipping section (3) that clips image data other than the image data to be displayed; and a drawing section (20) that displays the image data processed by the image processing section (20) on a display means. 6) In the three-dimensional image display device, the clipping unit (3) of the image processing unit converts each clip boundary plane forming the boundary of the area set in the coordinate system of the display surface back to the basic coordinate system. It includes a clip boundary plane inverse conversion unit (32), a pruning unit (33) that cuts off the figure if it protrudes from each of the inversely converted clip boundary planes, and a pruning unit (33) which precedes the field of view conversion unit (5). A three-dimensional graphic display device characterized in that the three-dimensional graphic display device is arranged as follows.