JP2951666B2 - Clipping method, graphic system and workstation - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clipping method and a graphic system having high drawing performance and a workstation provided with the graphic system, and is particularly suitable when a multi-window system is adopted. The present invention relates to a clipping method, a graphic system, and a workstation.

[Conventional technology]

When a graphic is displayed in a window opened on the screen and the graphic protrudes from the window, it is necessary to prevent the protruding portion from being displayed. In the conventional clipping method, a portion to be displayed in a window of a display target graphic is determined based on a window boundary line, only that portion is displayed in the window, and other portions are not displayed.

Incidentally, as related to the prior art, for example,
-117661 and JP-A-62-69372.

[Problems to be solved by the invention]

For example, as shown in FIG. 7, when a thick line 7 is displayed in a window B on a screen A, usually, auxiliary lines 2 and 3 parallel to the basic line 1 are calculated on both sides of the basic line 1 and the bit data is calculated. (FIG. 7 shows a gap between the lines 1 and 2 and between the lines 1 and 3 for convenience of explanation.
Actually, these gaps are not visible and are recognized as one thick line 7. ). For example, when the marker 4 is displayed, a marker display command is input and only the center point 5 is designated, so that a marker figure (x mark in this example) as shown in FIG. 7 is displayed. It has become so. In this way, when a marker or a thick line is displayed in the window B and another window C is opened as shown in FIG.
If a part of the marker 4 and a part of the thick line 7 that are not hidden in the window C are not displayed, an unnatural feeling is given. However, in the case shown in FIG. 8, since the center point 5 of the marker 4 is within the window C, the marker 4 is hidden in the drawing area (the window C of the window B in FIG. 8) in the conventional clipping method. Is determined to be out of the area (not shown), and no image is displayed. That is, instead of displaying a part as shown in FIG. 8, the whole is not displayed. Also, in the case of the thick line 7, when the entire center line 1 is hidden by the window C, the calculation of the auxiliary lines 2 and 3 is not performed, and only a part of the auxiliary line 2 is displayed in the drawing area of the window B as illustrated. Is not displayed.

Conventionally, in order to eliminate the above-mentioned inconveniences, a range in which a marker exists (a range including the entire X mark in the illustrated case) is conventionally used.
Is calculated one by one to determine whether or not this range is within the drawing area, and in the case of a thick line, check whether or not the auxiliary line is also within the drawing area, Is an algorithm that executes processing for displaying and does not give an unnatural feeling to an operator who views the screen. However, such a process, on the other hand, requires a long processing time, and thus has the problem of significantly lowering the drawing performance.

A first object of the present invention is to provide a clipping method capable of performing high-speed display processing of a graphic such as a marker or a thick line in a boundary area of a drawing area and having high drawing performance.

A second and third object of the present invention is to provide a graphic system and a workstation which can perform high-speed display processing of a graphic such as a marker or a thick line at a boundary portion of a drawing area and have high drawing performance. is there.

[Means for solving the problem]

The first object is to determine whether or not image data enters a clipping determination area provided corresponding to a drawing area of a display screen, and display the image data falling within the clipping determination area in the drawing area. In the method, an area including the drawing area as the clipping determination area and being wider than the drawing area by a predetermined amount is set, and it is determined whether or not the image data falls within the clipping determination area for each image data. Only the image data that enters the area is passed to the rendering processor to expand the pixels,
By prohibiting the display of the pixels outside the drawing area by displaying only the pixels inside the drawing area among the expanded pixels,
Achieved.

The second object is to provide a frame memory corresponding to a drawing area, display means for displaying pixel data developed and stored on the frame memory in the drawing area on a display screen, Determining whether or not the image data enters a clipping area wider than the drawing area by a predetermined amount; a rendering processor that expands pixels by passing only image data determined to be included by the determining means; This is achieved by providing means for storing only the pixels within the drawing area in the frame memory, and prohibiting the pixels outside the drawing area from being stored in the frame memory.

The third object is achieved by incorporating a graphic system that achieves the second object in a workstation.

[Action]

The conventional problem arises because the clipping determination area is the same as the actual drawing area. In the present invention, the clipping determination area for determining whether or not to perform rendering is performed in an area wider than the actual rendering area, and only the image data determined to be within the clipping determination area is passed to the rendering processor. In other words, since image data outside the clipping determination area is not subjected to pixel expansion by the rendering processor, processing time is not required. Then, image data that is not included in the drawing area in the pixel developed by the rendering processor is not stored in the frame memory, or even if stored, the stored data is not actually displayed. Processing becomes possible. Further, since the image at the boundary of the drawing area has continuity with an image that is not actually displayed outside the drawing area, an unnatural point does not occur in the displayed image.

〔Example〕

Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a diagram illustrating the principle of the present invention. For example, drawing A
When the window B is opened above and the window C is further opened, the drawing area of the window B becomes the shaded area 8. When window processing is performed on the image data to be displayed in the area 8 by the clipping method, first, in the present invention, an area including the drawing area 8 and being wider by ΔX and ΔY than the drawing area 8 (see FIG. 5). The area enclosed by the dotted line,
Hereinafter, the clipping area 9 will be referred to as a clipping area 9. ) Is performed to obtain image data that is within the clipping area 9 (determined to be drawn). Then, of the image data determined to be drawn, the image data in a range outside the clipping area 9 and outside the drawing area 8 is prohibited from being displayed when displayed. As a result, a display figure or the like in the boundary area of the drawing area 8 is not displayed unnaturally.

FIG. 2 is a configuration diagram of a portion related to a graphic system in a workstation according to an embodiment of the present invention. A graphic system according to an embodiment of the present invention includes:
A main processor 10, a shared memory 11, a graphics processor 12, a plurality of rendering processors 13, a bus 14 for interconnecting them, and a rendering processor 13.
A plurality of frame memories 16 connected by a dedicated bus 15 to
CRT 17 displaying information stored in these frame memories 16
And a dedicated bus 18 for connecting the shared memory 11 and the graphic processor 12, and a dedicated bus 19 for connecting the graphic processor 12 and the rendering processor 13.

Next, the basic operation of the graphic system having the above configuration will be described.

For example, to display the straight line drawing region of a window opened on the screen, the main processor 10, coordinates of both end points indicating that the command and the straight line that displays the coordinates and the straight line shown in the drawing area (x _i, y _i) and (X _{i + 1} , y _{i + 1} ) is written to the shared memory 11. Then, it instructs the graphic processor 12 to start up via the bus 14. The above coordinates are coordinates in a modeling coordinate system.

The activated graphic processor 12 has the shared memory 11
Then, the coordinates indicating the drawing area, the command, and the coordinates of the both end points are read out, the command is interpreted, and the coordinates indicating the drawing area and the coordinates of the both end points of the straight line are converted into the coordinates of the device coordinate system. The coordinates of the lower left corner of the converted drawing area are (X ₀ , Y ₀ ), the coordinates of the upper right corner are (X ₁ , Y ₁ ), and the coordinates of both ends of the straight line are (X _i , Y _i ) and (X _{i + 1).} , Y _{i + 1} ). And furthermore
The graphic processor 12 sets a clipping area for the drawing area, compares the boundary of the clipping area with device coordinates indicating both ends of the straight line, and determines whether the straight line is inside or outside the clipping area.

If it is determined that all the straight lines are inside the clipping area, the coordinates of both end points are passed to the rendering processor 13 via the dedicated bus 19. If it is determined that only a part of the straight line is inside the clipping area, the coordinates of the intersection of the straight line and the boundary of the clipping area are obtained, and the coordinates of the coordinates and the coordinates of the end point of the straight line in the clipping area are determined. Pass to 13. If it is determined that all the straight lines are outside the clipping area, there is no need to display this straight line, and the process ends.

The rendering processor 13 develops a pixel of a straight line connecting the two coordinate points based on the two coordinate points of the straight line passed from the graphic processor 12, and writes data to a memory cell in the frame memory 16 corresponding to the developed pixel. . At this time, pixel data of the developed pixels that are outside the drawing area are not written to the frame memory 16 as described later in detail.

By displaying the pixel data written in the frame memory 16 on the CRT 17 as described above, a straight line is displayed in the drawing area of the window. Further, even when only the auxiliary line enters the drawing area when displaying a thick line, the basic line enters the clipping area, so that the pixel data of the auxiliary line is written in the drawing area.

When displaying the marker in the drawing area, the coordinates indicating the drawing area, the display command of the marker, and the coordinates of the center point thereof are written in the shared memory 11. Graphic processor
The command interpreter 12 interprets this command and converts the coordinates of the center point and the coordinates indicating the drawing area into the coordinates of the device coordinate system. Then, it is determined whether or not the center point of the marker is in the clipping area. If so, the converted coordinates are passed to the rendering processor 13. The rendering processor 13 expands the pixel data forming the figure of the marker based on the passed coordinates of the center point, and stores the expanded pixel data in the corresponding memory cell of the frame memory 16. At this time, of the expanded pixels, pixel data outside the drawing area is not written into the frame memory 16 as described later in detail.

By displaying the pixel data written in the frame memory 16 on the CRT 17 as described above, a marker is displayed in the drawing area of the window. Even when the center point of the marker does not fall within the drawing area, the center point falls within the clipping area. Therefore, part of the pixel data that constitutes the figure of the marker and falls within the drawing area is also developed by the rendering processor 13 and the frame memory. Stored in 16. That is, only a part of the marker is displayed.

FIG. 1 is a detailed block diagram of the graphic processor 12 and the rendering processor 13 shown in FIG. 2 for implementing the above-described clipping method.

The graphic processor 12 includes registers 21 to 24 and registers 27 and 28, a selector 25 for selecting data from the shared memory 11 read through the dedicated bus 18 and data from the registers 21 to 24, and a processing device 26. .

The rendering processor 13 includes a processing unit 35 and boundary registers 31 to 34.

The processing device 26 of the graphic processor 12 reads and interprets the command from the shared memory 11, and if the command is a drawing command for a window, first reads the modeling coordinates of the lower left corner and the upper right corner of the drawing area via the selector 25. , Are converted into coordinates in the device coordinate system. The converted coordinates (X ₀ , Y ₀ ) and (X ₁ , Y ₁ ) are defined (see FIG. 5). Then, these coordinate values are sent to the rendering processor 13 and X ₀ −ΔX, Y ₀ −ΔY, X ₁ + ΔX, Y ₁ +
ΔY is calculated (these define the clipping area), and the calculation results are stored in registers 21 to 24, respectively. The processing procedure at this time is shown in the flowchart of FIG.
When the coordinates indicating the drawing area are directly written to the shared memory 11 as the device coordinate values (X ₀ , Y ₀ ) and (X ₁ , Y ₁ ), the main processor 10 performs a coordinate conversion process of the coordinate values. Is omitted.

Next, when drawing a straight line, the modeling coordinates at one end are read from the shared memory 11 and converted into device coordinates, and the converted coordinate values (X _i , Y _i ) are stored in the registers 27 and. Then, the data stored in the registers 27 and 28 and the register 21
Comparing the 24 stored data, it determines whether the end point (X _i, Y _i) enters the clipping region 9. When entering the clipping area 9, the coordinates of the end point are passed to the rendering processor 13. Next, the coordinates of the other end point of the straight line are read and the same processing as above is performed. If the end point does not fall within the clipping area 9, an intersection between the boundary of the clipping area 9 and the straight line to be drawn is obtained, and the coordinate value of the intersection is passed to the rendering processor 13. When a marker is drawn, the coordinates of the center point are converted into device coordinates and stored in registers 27 and 28, and it is determined whether or not the center point falls within the clipping region 9. To pass the coordinates of the center point.

In the rendering processor 13, coordinate values X ₀ , Y ₀ , X ₁ , and Y indicating the drawing area sent from the graphic processor 12.
₁ is stored in registers 31 to 34, respectively. If the object to be drawn is a straight line, pixel data forming a line connecting both points from the coordinate values of both end points or the coordinate values of the intersection and the end point is developed. If the drawing target is a marker, the center point of the marker develops the pixel data forming the marker graphic. Then, the address of the developed pixel data is compared with the values stored in the registers 31 to 34, and only the pixel data that falls within the drawing area 8 is written to the frame memory 16. Thus, the frame memory 16
Is displayed on the CRT 17, the image of the boundary area of the drawing area 8 is displayed in a natural state, and the operator does not feel unnatural.

The values of ΔX and ΔY that define the range extended from the drawing area are
It depends on the target image to be drawn. In the above-described embodiment, clipping is performed in the device coordinate system. To explain in this case, when the maximum size of the marker is 23 × 23 pixels on the device coordinates, half of this value, that is, 12 pixels is ΔX, ΔY, so that the purpose can be achieved. Further, even in the case of a thick line, the object can be achieved by setting the number of pixels to half the thickness. Therefore, this ΔX, Δ
The value of Y may be set in advance according to the type of image to be drawn by the graphic system or the like, or a means that can be designated from the outside may be provided so that the value can be arbitrarily set by an operator's instruction. When clipping is performed in a normalized device coordinate system, it is needless to say that the value needs to be converted into a value in the coordinate system.

Drawing is performed in pixel units, and screen scrolling
If it is performed in pixel units, it takes too much display time to give a troublesome feeling. Therefore, usually, a plurality of pixels, for example, 16 pixels or
32 pixels are displayed as one unit, and the screen is scrolled. When the clipping method of the present invention is applied to a graphic system employing such a method, pixel data outside the drawing area is not displayed, for example, of 16 pixels displayed near the boundary of the drawing area. You need to do that.

FIG. 3 is a detailed configuration diagram of a rendering processor in a graphic system that performs memory access between a rendering processor and a frame memory in units of 16 pixels. This rendering processor has coordinate values X ₀ , Y ₀ ,
In addition to the registers 31 to 34 for storing X ₁ and Y ₁ respectively, a pixel address generation unit 40 for expanding the pixels of the image to be displayed in 16-pixel units and generating an address for each unit, a register 41, and a comparator
42, 43, mask generation circuits 44 to 46, and an OR circuit 47.

The pixel address generator 40 converts the image data to be drawn into 16 based on the information sent from the graphic processor.
The data is developed as write data in which a pixel forms one raster, and the data is transmitted to the frame memory 16.
The address (Xl, Yl) is generated with 16 pixels as one unit and stored in the register 41. For example, X-direction address
Both the Xl and Y direction addresses Yl are 10-bit two-dimensional addresses. This address is also sent to the frame memory 16.

Comparator 42 is used to determine the address Xl in register 41 and the boundary register.
The comparator 43 compares the upper bits of the stored data of the 31, 33 with the exception of the lower bits, and the comparator 43 compares the address Yl in the register 41 with the stored data of the boundary registers 32, 34, and It is determined whether or not the data of 16 pixels enters the drawing area 8.

When 16 pixels at the address (Xl, Yl) enter the drawing area 8, all the write signals from the mask generation circuits 44 to 45 are ORed.
The data of 16 pixels output to the circuit 47 and output from the pixel address generation unit 40 to the frame memory 16 by the output signal of the OR circuit 47 is written to the memory cell at the address (Xl, Yl).

When it is determined that 16 pixels at the address (Xl, Yl) are outside the drawing area 8, a write inhibit signal is output from the mask generation circuit 46.
The write inhibition signal is output to the OR circuit 47 and is output from the OR circuit 47 to the frame memory 16. As a result, writing of 16-pixel data output from the pixel address generation unit 40 to the frame memory 16 is prohibited.

When the upper bits excluding the lower 4 bits of the address Xl and the upper bits excluding the lower 4 bits of the data stored in the boundary registers 31 and 33 are equal, that is, 16 pixels are applied to the boundary of the drawing area 8. If any of the pixels fall outside the drawing area 8, the comparison results are output from the mask generation circuits 44 to 46.
Is output to A write signal is output from the mask generation circuit 46.
It is output to the OR circuit 47, and a partial write inhibit signal is output to the OR circuit 47 from the mask generation circuit 44 or 45. For example, when there is a pixel out of the 16 pixels to the left of the left end (coordinate X ₀ ) of the drawing area 8, the mask generation circuit 44
A partial write inhibit signal for masking the protruding pixels is output to the OR circuit 47 from each bit information of the lower 4 bits of the address indicating 16 pixels. With the partial write inhibit signal output to the frame memory 16 through the OR circuit 47, the writing of pixel data that extends beyond the drawing area is inhibited.

In the same manner as described above, a partial write prohibition signal is generated by the mask generation circuit 45 for a pixel protruding to the right end (coordinate X ₁ ) 9 of the drawing area 8.

In each of the above-described embodiments, of the image data determined to be drawn in the clipping region 9, the image data serving as the actual drawing region is not written in the frame memory 16, and the image of that portion is not displayed. However, instead of this method, it is also possible to prohibit display of image data outside the drawing area by the following method. As shown in FIG. 6, all the image data 51 developed by the rendering processor are stored in a plane 50 having a frame memory, and another plane 52 is provided at a position (hatched region) corresponding to the drawing region 53. Store "0" in the data corresponding to "1" in the area corresponding to the other area, and take the logical product of the data stored in the corresponding pixel positions of both planes 50 and 52 when displaying on the CRT. However, display of image data outside the drawing area and inside the clipping area can be prohibited.

〔The invention's effect〕

According to the present invention, there is an effect that an unnatural point is eliminated in a display image in a boundary area of a drawing area and pixel data outside the clipping determination area is not passed to the rendering processor, so that an image display processing time is shortened.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a graphic processor and a rendering processor constituting a graphic system according to an embodiment of the present invention. FIG. 2 is a configuration diagram of a graphic system incorporated in a workstation according to an embodiment of the present invention. The figure shows a configuration example of a rendering processor, FIG. 4 is a flowchart showing one processing procedure in a graphic processor, FIG. 5 is a diagram for explaining the principle of the present invention, and FIG. 6 is an image in a clipping area outside a drawing area. FIG. 7 and FIG. 8 are explanatory diagrams of an embodiment for prohibiting data display, and FIG. 7 and FIG. A: display screen, B, C ... window, 1 ... center line,
2,3 ... Auxiliary line, 4,51 ... Marker, 5 ... Center point, 7 ...
... thick line, 8,53 ... drawing area, 9 ... clipping area,
10: Main processor, 11: Shared memory, 12: Graphic processor, 13: Rendering processor, 14
… Bus, 15, 18, 19… Dedicated bus, 16… Frame memory, 17… CRT, 21 to 24, 27, 28… Register, 25, 35…
Processing device, 31-34 Boundary register, 40 Pixel address generator 41, Register 42, 43 Comparator 44-46
…… Mask generation circuit, 50,52 …… Plane.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuyoshi Koga 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory, Ltd. (72) Inventor Hideyuki Hara 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Co., Ltd. Inside the Hitachi, Ltd. Omika Plant (56) References JP-A-63-175982 (JP, A)

Claims (7)

(57) [Claims] 1. A method for determining whether image data for drawing a straight line is included in a clipping determination area provided corresponding to a drawing area of a display screen, and determining whether or not image data falling within the clipping determination area is included in the drawing area. In the clipping method of displaying only a portion, the graphic processor sets an area that includes the drawing area as a clipping determination area and is wider by a predetermined amount than the drawing area, and image data for drawing a straight line is included in the clipping determination area. It is determined from the coordinate information of the end point of the straight line whether or not the image data is included. When entering the judgment area, the coordinate information of the end point in the clipping judgment area and the image data for drawing a straight line are The coordinate information of the intersection with the boundary line of the clipping determination area is passed to the rendering processor, and the rendering processor expands the pixel based on the coordinate information, and among the expanded pixels, the pixels that are in the rendering area And prohibiting the display of pixels outside the drawing area. 2. A clipping method according to claim 1, wherein said predetermined amount is set according to a graphic constituted by image data to be displayed. 3. A frame memory corresponding to a drawing area, display means for displaying pixel data developed and stored on the frame memory in the drawing area on a display screen, and including the drawing area as a clipping determination area. An area wider than the drawing area by a predetermined amount is set, and it is determined whether or not image data for drawing a straight line falls within the clipping determination area from the coordinate information of the end point of the straight line. Draws the coordinate information of both end points when entering the clipping judgment area, and draws the coordinate information and the straight line of the end point within the clipping judgment area when only one end point of the image data enters the clipping judgment area. A graphics processor that outputs coordinate information of an intersection of the image data and a boundary line of the clipping determination area, A pixel is developed based on the coordinate information of the end point entering the clipping determination area or the coordinate information of the end point and the coordinate information of the intersection with the boundary line of the clipping determination area output from the processor. A graphics system, comprising: a rendering processor that stores pixels inside the drawing area in the frame memory and prohibits pixels outside the drawing area from being stored in the frame memory. 4. The graphic system according to claim 3, further comprising means for designating the predetermined amount. 5. The apparatus according to claim 3, wherein said means for prohibiting the rendering processor from storing pixels outside the drawing area in the frame memory includes: a boundary register storing boundary data of the drawing area; A pixel address generation unit that divides the data into a plurality of pixel units in the direction and generates an address for each unit; a comparator that compares upper bit data of the data stored in the boundary register with an address from the address generation unit; According to the comparison result, when one unit of the plurality of pixel data indicated by the address exists outside the boundary of the drawing area, the pixel data outside the drawing area is masked based on the lower bit data of the data stored in the boundary register. A graphic system comprising mask means for preventing the image data from being stored in a frame memory. 6. A frame memory, display means for displaying pixel data developed and stored on the frame memory in a drawing area on a display screen, and including the drawing area as a clipping area by a predetermined amount from the drawing area. When a wide area is set and it is determined from the coordinate information of the end point of the straight line whether or not image data for drawing a straight line falls within the clipping determination area, and both end points of the image data fall in the clipping determination area. In the case where only one end point of the image data falls within the clipping determination area, the coordinate information of both end points and the coordinate information of the end point within the clipping determination area and the image data for drawing a straight line. A graphic processor that outputs coordinate information of an intersection with a boundary line of the clipping determination area; A rendering processor that expands pixels based on coordinate information of an end point entering the clipping determination area or coordinate information of the end point and an intersection with a boundary line of the clipping determination area, and stores the expanded pixels in the frame memory. And a mask means for displaying pixels in the drawing area among the pixels developed on the frame memory and prohibiting display of pixels outside the drawing area. 7. A workstation incorporating the graphics system according to claim 3. Description: