JPH07210707A - Method and device for plotting edge figure - Google Patents

Abstract

PURPOSE:To distinctively paint a figure even if pixels corresponding to the edge and pixels corresponding to the inside of the figure overlap with each other when the edge and inside of the figure are plotted while a hidden surface process and a hidden line process are performed in consideration of the depth of each pixel of the figure. CONSTITUTION:A specific value S is written in a depth buffer memory instead of depth data on the respective pixels corresponding to the edge of the figure step 3. Only unless depth data on the respective pixels corresponding to the inside of the figure which are stored in the depth buffer show the specific value S, the color data of the pixels are written in a frame buffer and the depth data of the pixels are written in the depth buffer memory (step 8). Then the respective pixels corresponding to the edge of the figure are retrieved again and when the data stored corresponding to the pixels show the specific value S, the contents of the depth buffer memory are rewritten into the depth data of the pixels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION When drawing a three-dimensional figure in computer graphics, a method of dividing the figure into polygons (polygons) and drawing each polygon is used. Further, depending on the content of drawing, it may be necessary to emphasize and display the edge of the polygon.

The present invention relates to a method and apparatus for drawing a graphic with an edge for drawing the edge and the inside of such a polygon.

[0003]

2. Description of the Related Art When carrying out the above-mentioned drawing method, two-dimensional coordinate data (hereinafter simply referred to as "coordinate data") of the vertices of the polygon, and depth data are provided along with color data for painting the edges and interiors of the polygon. Needs to be given to the drawing processor. When drawing a polygon having such a depth, the drawing processor linearly interpolates the coordinate data and depth data of each point on the edge of the polygon using the coordinate data and depth data of the vertex of the polygon, The coordinate data and depth data of each point inside the polygon are obtained by surface interpolation using the coordinate data and depth data of the vertices of the polygon. Draw a polycon so that it is hidden.

However, in the polygon drawing process,
The points on the edge may be points inside the polygon at the same time, but there is generally no guarantee that the depth data on the edge at the same point and the depth data inside the polygon are the same. Therefore, for example, if you draw the edge first and then draw the inside of the polygon later, if the depth data inside the polygon is the closest value, the edge is erased at that point, the edge is displayed as a dotted line, and the edge is displayed. There is an inconvenience that the purpose of highlighting is not achieved.

Therefore, a mask buffer is prepared,
A drawing method has been proposed in which a pixel in a mask buffer corresponding to an edge is masked to draw a pixel corresponding to the edge, and then a pixel corresponding to the inside of the polygon is drawn by referring to the contents of the mask buffer ( See JP-A-3-139781). According to this proposal, there is no need to draw edges in an overlapping manner, so that the above-mentioned inconvenience can be solved.

[0006]

However, according to the technique disclosed in Japanese Patent Laid-Open No. 3-139781, an additional mask buffer is required in addition to the color buffer and the depth buffer, which complicates the configuration. There's a problem. Therefore, the present invention solves the above-mentioned technical problem, and provides a drawing method and apparatus for an edged figure that can draw the edges and the inside of a polygon without using a mask buffer while emphasizing the edges. .

[0007]

According to a first aspect of the present invention, there is provided a method of drawing a graphic with an edge, wherein each pixel corresponding to an edge of the graphic is searched for and replaced with depth data of the pixel. Write a specific value S to the depth buffer memory, search for each pixel corresponding to the inside of the figure,
Only when the depth data stored in the depth buffer memory corresponding to the pixel does not represent a specific value S, the color data of the pixel is written in the frame buffer memory, and the depth data of the pixel is depth-coded. Write to the buffer memory, search again each pixel corresponding to the edge of the figure, and if the data stored corresponding to the pixel represents a specific value S, the depth buffer memory is set to the depth data of the pixel. Rewriting to, the operation of writing the color data of each pixel corresponding to the edge of the figure to the frame buffer memory is performed during any of the above steps,
This is a method of drawing the edge and the inside of a figure based on the written data of the frame buffer memory and the depth buffer memory.

An edged figure drawing apparatus according to a second aspect is an apparatus according to the same invention for realizing the method according to the first aspect. The drawing method of the figure with an edge according to claim 3 is
Compared with the drawing method of an edged figure according to claim 1, a specific value S is written in a frame buffer memory.

According to a fourth aspect of the present invention, there is provided an apparatus for drawing a graphic with edges, which is an apparatus according to the same invention for realizing the method according to the third aspect. The edge of the figure may be a solid line, or may be a broken line or a dotted line consisting of an on portion and an off portion (claim 5).

[0010]

According to the first or second aspect of the present invention, first, the specific value S is written in the depth buffer memory in place of the depth data of each pixel corresponding to the edge of the figure.
Then, the depth data stored in the depth buffer memory of each pixel corresponding to the inside of the figure is a specific value S.
The color data of the pixel is written in the frame buffer memory and the depth data of the pixel is written in the depth buffer memory only when it does not represent the pixel.

As a result, when a pixel forming a graphic overlaps with a pixel corresponding to the edge of the graphic, each pixel corresponding to the inside of the graphic can be filled without painting the pixel corresponding to the edge. it can. Next, each pixel corresponding to the edge of the figure is searched again, and if the data stored corresponding to the pixel indicates the specific value S, the depth buffer memory is rewritten with the depth data of the pixel. It As a result, the original depth data of the pixel can be given to the pixel corresponding to the edge.

The operation of writing the color data of each pixel corresponding to the edge of the figure in the frame buffer memory is as follows.
It may be performed during any of the above procedures. In this way, the edge and the inside of the figure can be drawn based on the written data in the frame buffer memory and the depth buffer memory. According to the third or fourth aspect of the invention, instead of the color data of each pixel corresponding to the edge of the figure, a specific value S is written in the frame buffer memory, which corresponds to the inside of the figure. Only when the color data stored in the frame buffer memory of each pixel does not represent the specific value S, the color data of the pixel is written in the frame buffer memory, and the depth data of the pixel is stored in the depth buffer memory. Write. Therefore, when a pixel forming a graphic overlaps with a pixel corresponding to the edge of the graphic, each pixel corresponding to the inside of the graphic can be filled without painting the pixel corresponding to the edge. It is possible to obtain the same effect as that of the invention of Item 1 or 2.

According to the fifth aspect of the present invention, if at least the on-part of the edge is processed according to the first or third part, the on-part of the edge and the inside are drawn without overlapping.

[0014]

Embodiments will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 3 is a block diagram showing the arrangement of a drawing apparatus for drawing an edged polygon. The drawing device
A graphics controller 1 that functions as a "drawing processor" connected to a host computer, a frame buffer (hereinafter referred to as "color buffer") 2 that stores color values corresponding to each figure, and the depth of pixels that make up each figure. It has a depth buffer (hereinafter referred to as “Z buffer”) 3 for storing data (hereinafter referred to as “Z value”) and a raster scan drawing monitor display device 4. The pixel size of each of the color buffer 2 and the Z buffer 3 is M × N according to the pixel size of the screen, and the depth data size of the Z buffer 3 is usually about 8 bits to 32 bits. The color values are the three primary colors R, G,
In the case of monochrome display, only the brightness may be used, and the index may be a color value.
In the case of an index, a means for converting the index into data of the three primary colors R, G, B by a look-up table or the like is required between the color buffer 2 and the drawing monitor display device 4.

FIG. 4 is a block diagram for explaining the inside of the graphics controller 1. The graphics controller 1 is based on a drawing command signal including a vertex coordinate value, a Z value and a color value of a polygon received from a host computer. , An edge processor 11 for obtaining the coordinate values, color values and Z values of polygon end points located on the same scan line while performing a planar interpolation operation, and the coordinates of the two end points or the two vertices of the edge given from the host computer. A span filler 12 that receives values, color values and Z values and linearly interpolates between two points to generate coordinate values, color values and Z values on a line segment.
And the color values inside edges and polygons are stored in color buffer 2
And a buffer controller 13 for writing and updating the Z value inside the edge and the polygon inside the Z buffer 3.

In the following, for example, when the edges and the inside of a triangular polygonal figure as shown in FIG. 5 are drawn in a specific color, the data is color buffer 2 and Z buffer 3
The procedure to be stored in will be described in detail with reference to the flowchart (FIGS. 1 and 2). Incidentally, the polygon figure may be an arbitrary polygon such as a quadrangle other than the triangle. This procedure is roughly divided into a process of assigning a specific value S to an address corresponding to an edge pixel of the Z buffer 3, and a process of assigning a color value C to an address corresponding to a pixel inside a polygon of the color buffer 2. It is composed of a process of assigning an original Z value to an edge pixel to which the specific value S is assigned.

Here, the specific value S is set to the deepest value, for example, all bits of the Z buffer 3 are "1" or all bits are "0". However, the present invention is not limited to this, and one intermediate value may be determined and set. In this case, the value interpolated in the edge processor 11 or the span filler 12 needs to exclude the specific value S. Process of assigning a specific value S to an address corresponding to an edge pixel of the Z buffer 3 (step (1) -step (4)
): First, the host computer gives an edge drawing command to the span filler 12 and gives an S set signal to the buffer controller 13. In the span filler 12, the edge processor 11 performs interpolation calculation to find each pixel at the edge, and obtains the coordinate value, Z value and color value C of the pixel (step (1)). And buffer controller 1
3 refers to the Z value of that pixel and compares it with the old Z value previously stored in the Z buffer 3. If the Z value is data that is before the old Z value (step (2)), the color of the pixel at the edge is written in the color buffer 2 and the specific value S is written in the Z buffer 3 (that is, the Z buffer is Update, step (3)). If not, skip step (3). The above processing is performed for all edge pixels (step (4)). Process of assigning the color value C to the address corresponding to the pixel inside the color buffer 2 polygon (step (5) -step (9)): Next, the host computer gives a polygon drawing command signal to the edge processor 11, and the buffer controller Thirteen
To the S skip signal. The edge processor 11 uses the coordinate values of both end points of polygons on the same scan line,
The color value and the Z value are obtained by sequentially scanning the scan line from the top to the bottom (or from the bottom to the top), and passed to the span filler 12 each time they are obtained. The span filler 12 regards the distance between the end points as a straight line, and obtains the coordinate value, color value and Z value on the line segment (step
(Five) ).

Then, the buffer controller 13 refers to the old Z value of the pixel inside the polygon previously stored in the Z buffer 3 and checks whether it is equal to the specific value S (step (6)). If it is not the specific value S, the Z value of the point inside the polygon is compared with the old Z value. If the Z value is data that is before the old Z value (step (7)), the color value of the pixel inside the Z value is written in the color buffer 2 and the Z value of the pixel inside the Z value is written in the Z buffer 3 ( Step
(8)). However, when the old Z value is equal to the specific value S in step (6), step (7), step
Skip (8). That is, the color buffer 2 is not written. Among the pixels inside the polygon, the pixel having the specific value S as the Z value is also the edge pixel, and thus it is possible to prevent the color of the edge pixel from being applied twice. The above processing is performed for all pixels inside the polygon (step (9)). However, when the specific value S is assigned to the shallowest value, the specific value S
There is no need for step (6) to check if the value is equal to, and writing to pixels whose old Z value is S (steps (7), (8)) is skipped by comparison with the normal Z value. Therefore, in this case, steps (5)-(9) are the same as the normal polygon drawing procedure, and it is not necessary to give the S skip signal to the buffer controller 13. The original Z is assigned to the edge pixel to which the specific value S is assigned.
Value assigning process (step (11) -step (14)): In this process, the pixel at the edge to which the specific value S is assigned as the Z value is searched again and the original Z value is assigned.

First, the host computer gives an edge drawing command signal to the span filler 12 and an S clear signal to the buffer controller 13. The span filler 12 performs interpolation calculation to find each edge pixel, and obtains the coordinate value, color value and Z value of the pixel (step (11)). The buffer controller 13 then determines whether the old Z value previously stored in the Z buffer 3 for that pixel is equal to the S value. If they are equal (step (1
2)), write the original Z value to the Z buffer 3 (step
(13)). If the old Z value is not equal to the S value, step (13)
Skip. The above processing is performed for all edge pixels (step (14)).

As described above, the color value, the coordinate value, and the Z value of the edge and the inside of the polygon are stored in the color buffer 2 and the Z buffer 3 for each polygon. After that, as usual, the color buffer 2 and the Z buffer 3
Drawing of polygons is performed while erasing hidden surfaces and hidden lines based on the data stored in. As described above, according to the embodiment, the pixel corresponding to the edge is given the specific value S instead of the depth data. Therefore, the pixels forming the inside of the polygon are the pixels corresponding to the edge of the polygon. This can be detected in advance if it overlaps with. Therefore, the pixel corresponding to the edge and each pixel corresponding to the inside of the polygon can be painted in a predetermined color without overlapping each other.

In the embodiment, since the specific value S is assigned inside the Z buffer, the original data for displaying the depth is reduced by one. However, since the Z buffer itself normally has 8-bit-32-bit data (the number of data is 2 ⁸ -2 ³² ) as depth data, even if one of these cannot be used, no inconvenience occurs. Considered to be few.

Further, in comparison with the normal processing, in the embodiment, each pixel corresponding to the edge of step (11) -step (14) is searched again, and the data stored corresponding to the pixel is specified. If it represents the value S of, the process of rewriting the Z buffer memory to the original Z value of the pixel is required, which causes an increase in processing time. However, the number of pixels corresponding to an edge is Since it is much smaller than the number, the ratio of the increasing processing time to the total processing time is extremely small.

The present invention is not limited to the above embodiment. In the embodiment, the specific value S is written in the Z buffer memory for each pixel corresponding to the edge of the polygon, but the specific value S is written in the color buffer memory for each pixel corresponding to the edge of the polygon. , A similar effect can be obtained. In this case, in the “edge processing” in the flowcharts of FIGS. 1 and 2, the specific value S is written in the color buffer as the color value of the edge, and in the “internal processing”, the internal color value is compared with the specific value S, In the "edge reprocessing", the true color value of the edge is written in the Z buffer. In particular,
It becomes like FIG. 6-FIG. In this case, since there is a period in which the specific value S is displayed as a color value, it is safe to give black (no brightness) as the specific value.

Further, in the above embodiments, the shape of the edge is assumed to be a solid line as shown in FIG. 5, but it is not limited to this, and the edge is a broken line or a dotted line consisting of an ON part and an OFF part. Good. For example, if it is an on-off dash (a broken line that draws an on portion but does not draw an off portion), only the on portion is processed in the “edge processing” and “edge reprocessing” in FIGS. The part of can be treated as an inside instead of an edge and processed. By doing this, the color inside the polygon is added to the off part.

In addition to the above, the "off edge processing" and "edge reprocessing" may be performed by regarding both the on portion and the off portion as edges. In this case, the steps in Figure 1
In (3) “Write edge color to color buffer” process, the color value of the off part is not written, and in “(Write true color value to color buffer)” process of step (13) in FIG. The value C is returned to the original color value. This way
It cuts into the part where the background color is off.

If it is a double dash (a broken line for drawing an on portion and an off portion in different colors), the on portion as well as the off portion are regarded as edges, and "edge processing" is performed.
Or "edge reprocessing". And the steps of FIG.
In the process of "writing the edge color to the color buffer" in (3) and the process of "writing the true color value in the color buffer" in step (13) of FIG. 7, the on part and the off part are separated. Write on the color. This makes it possible to draw the broken lines in different colors.

[0027]

As described above, according to the drawing method or apparatus of the figure with an edge of the present invention, a specific value S is given to the pixel corresponding to the edge, so that a special buffer memory such as a mask buffer is provided. Even if the pixel is not provided, it can be detected in advance when the pixel forming the inside of the graphic overlaps with the pixel corresponding to the edge of the graphic. Therefore, the pixel corresponding to the edge and each pixel corresponding to the inside of the figure can be painted in a predetermined color without overlapping each other, and the edge of the polygon can be emphasized and displayed.

In particular, when the edge of the figure is a broken line or a dotted line consisting of an ON part and an OFF part, at least the ON part of the edge can be drawn without overlapping with the inside, and as a result, Edges can be emphasized and displayed.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating a procedure for storing various data in a color buffer 2 and a Z buffer 3.

FIG. 2 is a flowchart (continuation of FIG. 1) illustrating a procedure for storing various data in a color buffer 2 and a Z buffer 3.

FIG. 3 is a block diagram showing a configuration of a drawing device for drawing a polygon with edges.

FIG. 4 is a block diagram illustrating an internal configuration of a graphics controller.

FIG. 5 is a diagram showing polygons whose edges and inside are drawn in specific colors.

FIG. 6 is a flowchart according to another embodiment for explaining a procedure for storing various data in the color buffer 2 and the Z buffer 3.

FIG. 7 is a flowchart (continuation of FIG. 6) according to another embodiment illustrating a procedure for storing various data in the color buffer 2 and the Z buffer 3.

[Explanation of symbols]

 1 Graphic Controller 2 Color Buffer 3 Z Buffer 4 Monitor Display Device 11 Edge Processor 12 Span Filler 13 Buffer Controller

Claims (5)

[Claims] 1. A method of drawing an edge and an inside of a figure while considering the depth of each pixel of the figure, comprising:
Each pixel corresponding to the edge of the figure is searched, a specific value S is written in the depth buffer memory in place of the depth data of the pixel, (b) Each pixel corresponding to the inside of the figure is searched, and the pixel Only when the depth data stored in the depth buffer memory corresponding to does not represent the specific value S, the color data of the pixel is written in the frame buffer memory, and the depth data of the pixel is written in the depth buffer memory. And (c) search each pixel corresponding to the edge of the figure again, and if the data stored corresponding to the pixel represents a specific value S, the depth buffer memory is set to the depth of the pixel. Rewrite to data,
(d) The operation of writing the color data of each pixel corresponding to the edge of the figure in the frame buffer memory is the same as in (a) or
Perform during any of the steps in (c), (e) above (a)-(d)
A method of drawing a figure with an edge, characterized in that the edge and the inside of the figure are drawn based on the data of the frame buffer memory and the depth buffer memory written by the procedure of. 2. A drawing monitor device, a frame buffer memory for storing color data for each pixel forming a screen displayed on the drawing monitor device, and depth data for each pixel corresponding to a figure to be drawn. In a drawing device including a depth buffer memory that draws data, and a drawing processor that draws the edge and the inside of a figure based on the data in the frame buffer memory and the depth buffer memory, the drawing processor determines each pixel corresponding to the edge of the figure. A means for searching and writing a specific value S in the depth buffer memory instead of the depth data of the pixel, and each pixel corresponding to the inside of the figure are searched and stored in the depth buffer memory corresponding to the pixel. Determining means for determining whether or not the depth data that is present represents a specific value S; If it is determined that the depth data stored in the depth buffer memory corresponding to the pixel does not represent the specific value S, the color data of the pixel is written in the frame buffer memory and A means for writing the depth data in the depth buffer memory, and searching again each pixel corresponding to the edge of the figure, and if the data stored corresponding to the pixel indicates a specific value S, the depth buffer A drawing device for an edged graphic, comprising means for rewriting the memory to the depth data of the pixel and means for writing color data of each pixel corresponding to the edge of the graphic to the frame buffer memory. 3. A method of drawing an edge and the inside of a graphic while considering the depth of each pixel of the graphic, comprising:
Each pixel corresponding to the edge of the figure is searched, a specific value S is written in the frame buffer memory instead of the color data of the pixel, and (b) each pixel corresponding to the inside of the figure is searched and the pixel Only when the color data stored in the frame buffer memory corresponding to the above does not represent the specific value S, the color data of the pixel is written into the frame buffer memory, and the depth data of the pixel is stored in the depth buffer memory. And (c) each pixel corresponding to the edge of the figure is searched again, and if the color data stored corresponding to the pixel indicates a specific value S, the frame buffer memory of the pixel is stored. Rewriting to the original color data, (d) The operation of writing the depth data of each pixel corresponding to the edge of the figure to the depth buffer memory is the same as in (a) above.
Or during any of the procedures in (c), (e) above (a) −
A drawing method of an edged figure, which is characterized by drawing the edge and the inside of the figure based on the data of the frame buffer memory and the depth buffer memory written by the procedure of (d). 4. A drawing monitor device, a frame buffer memory for storing color data for each pixel forming a screen displayed on the drawing monitor device, and depth data for each pixel corresponding to a figure to be drawn. In a drawing device including a depth buffer memory that draws, and a drawing processor that draws the edge and the inside of a figure based on the data of the frame buffer memory and the depth buffer memory, the drawing processor determines each pixel corresponding to the edge of the figure. A means for retrieving and writing a specific value S in the frame buffer memory instead of the color data of the pixel and each pixel corresponding to the inside of the figure are retrieved and stored in the frame buffer memory corresponding to the pixel. Determining means for determining whether or not the color data that is present represents a specific value S; If it is determined that the color data stored in the frame buffer memory corresponding to the pixel does not represent the specific value S, the color data of the pixel is written in the frame buffer memory and A means for writing the depth data in the depth buffer memory, and a search for each pixel corresponding to the edge of the figure again, and if the data stored corresponding to the pixel indicates a specific value S, the frame buffer An apparatus for drawing a graphic with an edge, comprising means for rewriting the memory with the original color data of the pixel and means for writing the depth data of each pixel corresponding to the edge of the graphic into the depth buffer memory. 5. The drawing method for an edged graphic according to claim 1, wherein the edge of the graphic is a solid line, or a broken line or a dotted line consisting of an ON part and an OFF part.