JPH0740310B2 - Cross-section drawing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sectional view drawing apparatus, and more specifically, for displaying a state in which a desired portion of a three-dimensional figure is cut in a three-dimensional graphic display apparatus. The present invention relates to a cross-sectional drawing device.

<Prior Art> Conventionally, in a three-dimensional graphic display device, since the hidden surface processing function and the cross-section processing function play important roles, it is essential to have both of the above functions.

FIG. 2 is a block diagram showing a conventional example of a three-dimensional graphic display device having a hidden surface processing function and a cross-section processing function, and a coordinate conversion processor (11) to which coordinate data is supplied from a host computer (not shown), A clip processor (12) to which the device coordinate data converted by the coordinate conversion processor (11) is supplied,
The drawing processor (1) to which the primitive data clipped by the clip processor (12) is supplied.
3), the drawing memory (14) to which the pixel data output from the drawing processor (13) is supplied, and the pixel data output from the drawing processor (13) are supplied so that they have been set previously. A Z buffer (15) for supplying a write enable signal to the drawing memory (14) based on the coordinate data, and a monitor (16) for performing visual display based on the pixel data stored in the drawing memory (14).
It has and. In the description of FIG. 2, the Z buffer (15) is used as having a function of holding the z value and a function of performing processing based on the Z buffer algorithm.

Accordingly, the coordinate data supplied from the host computer is converted into device coordinate data by the coordinate conversion processor (11), and the primitive data outside the area designated by the user is clipped by the clip processor (12), and the rendering processor ( Supply to 13). Then, the drawing processor (13) supplies (x, y, z) data to the Z buffer (15) while interpolating each point of the primitive data in the designated area in each direction of x, y, z. (X, y) data is supplied to the drawing memory (14).

In the Z buffer (15), the z value for each (x, y) data is stored, and the pixel data (x, y, z1) is compared with the currently stored (x, y, z0), If 0 ≦ z1 ≦ z0, a write enable signal is supplied to the drawing memory (14) to display (x, y, z1), and z1 is set as a new z0. Conversely, when z0 <z1, the write enable signal is not output. Therefore, the hidden surface processing can be performed by sequentially updating the z0 value using the Z buffer (15).

Further, when the cross-section is displayed, the z value of the cross section is supplied to the clip processor (12) in advance, and each primitive data clipped with respect to x and y is supplied to the clip processor (12) again. The primitive data before the z value is eliminated, and when intersecting, the clipping data is clipped, and the obtained limiting data may be supplied to the drawing processor to display the cross section of the three-dimensional figure.

<Problems to be Solved by the Invention> When the cross-section display function of the above configuration is executed, the midpoint division method and the linear equation substitution method are used to obtain the intersection with the cross section. However, there is a problem in that the software and hardware are complicated and the processing time becomes long. That is, in the midpoint division method, the processing is slowed down as a result of slow convergence, and in the linear equation substitution method, since multiplication and division must be performed, the processing becomes complicated and the processing becomes slow. It will be.

Further, since the z value of the cross section is supplied to the clip processor (12), only one cut plane of the plane can be defined, and cross section display based on the free curved surface cannot be performed at all. There is also a problem.

<Objects of the Invention> The present invention has been made in view of the above problems,
An object of the present invention is to provide a cross-section drawing device that can simplify the system configuration and can easily perform cross-section display with a certain degree of accuracy based on various cut surfaces.

<Means for Solving Problems> To achieve the above object, a cross-sectional view drawing apparatus of the present invention includes a Z buffer, az value included in pixel data output from a drawing processor, and a corresponding pixel. Of the z values written to the Z buffer before data processing, the size is compared with the z value corresponding to the x, y value included in the pixel data output from the drawing processor, and included in the pixel data. Z
It is determined whether or not the value is in front, and the z value written in the Z buffer is updated with the z value included in the pixel data, provided that the z value included in the pixel data is in front. Z buffer algorithm processing means, a sectioning buffer that holds a Z value that defines a section, a z value included in pixel data output from the drawing processor, and a section that is written in advance in the sectioning buffer. Of z values, z corresponding to x, y values included in pixel data output from the drawing processor
The z value included in the pixel data is forwarded by the comparison logical operation processing means for comparing the magnitude with the value to determine whether or not the z value included in the pixel data is on the back side. To the drawing memory in response to the comparison result signal indicating that the z value included in the pixel data is on the back side is output from the comparison logic operation processing means. And a writing control means for permitting writing of pixel data.

However, it is written in the sectioning buffer in advance,
The z value that defines the cross section may be a z value that defines a free-form surface.

<Operation> In the case of the cross-section drawing apparatus having the above configuration, the pixel data to be drawn is transmitted from the drawing processor to the drawing memory,
When displaying a three-dimensional figure on the display based on the contents of the drawing memory, the z value included in the pixel data output from the drawing processor and the z value written in the Z buffer before the corresponding pixel data is processed. Of the z values, the z value corresponding to the x and y values included in the pixel data output from the drawing processor is compared by the Z buffer algorithm processing means of the size, and the z value included in the pixel data is in front. Whether to determine whether or not
The z value written in the Z buffer is updated with the z value included in the pixel data on condition that the z value included in the pixel data is in front. Further, among the z value included in the pixel data output from the drawing processor and the z value that is written in the sectioning buffer in advance and defines the cross section, x, y included in the pixel data output from the drawing processor. The magnitude of the z value corresponding to the value is compared by the comparison logical operation processing means to determine whether or not the z value included in the pixel data is on the back side.
Then, the Z-buffer algorithm processing means outputs a discrimination result signal indicating that the z value included in the pixel data is in front, and the comparison logical operation processing means outputs the z value included in the pixel data in the back side. In response to the output of the comparison result signal indicating, the writing control unit permits writing of the pixel data in the drawing memory. Therefore, it is possible to write the pixel data from the drawing processor to the drawing memory.

That is, the Z-buffer algorithm processing means defines a section which is determined to be located on the front side of the z-value written in the Z-buffer and which is previously written in the sectioning buffer by the comparison logical operation means. z
Only the pixel data determined to be located deeper than the value can be written in the drawing memory, and the hidden surface treatment is performed only by displaying the three-dimensional figure on the display based on the contents of the drawing memory. It is possible to display a sectional view with a certain degree of accuracy.

It is also pre-written in the sectioning buffer,
Even when the z value defining the cross section is the z value defining the free-form surface, the comparison result signal can be generated by performing the comparison logic operation by the comparison logic operation processing means, and the comparison result signal can be displayed in the drawing memory. Only the corresponding pixel data is stored.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 1 is a block diagram showing an embodiment of a graphic display device including a sectional view display device of the present invention.
A coordinate conversion processor (1) to which coordinate data is supplied from a host computer (not shown), a clip processor (2) to which device coordinate data converted by the coordinate conversion processor (1) is supplied, and a clip processor (2) The drawing processor (3) to which the primitive data clipped by is supplied, the drawing memory (4) to which the pixel data output from the drawing processor (3) is supplied, and the drawing processor (3) are output. By supplying the pixel data, a process based on the Z buffer algorithm is performed based on the z value included in the pixel data and the z value already stored in the Z buffer, and the z value included in the pixel data is calculated. Outputs a write enable signal to the drawing memory (4) in response to being on the front side Rutotomoni, Z-buffer algorithm processor for updating the z value z values contained in the pixel data is written to the Z buffer on condition that in front with z values contained in the pixel data (5)
And the pixel data output from the drawing processor (3) are supplied to compare the z value included in the pixel data with the preset z value that defines the cross section, A comparison logic operation processing unit (6) that outputs a write enable signal to the drawing memory (4) in response to the z value included in the data being on the back side, and pixel data stored in the drawing memory (4). And a monitor (7) for making a visual display based on the above. Then, the Z buffer algorithm processing unit (5)
AND the write enable signal output from the comparison logic operation processing unit (6)
It is supplied to the control terminal of the drawing memory (4) through the gate (8).

The operation of the graphic display device having the above configuration is as follows.

The coordinate data supplied from a host computer (not shown) is converted into device coordinate data by the coordinate conversion processor (1) and then supplied to the clip processor (2), so that the primitive outside the area designated by the user. The data is eliminated or clipped and supplied to the drawing processor (3). Then, in the drawing processor (3), the Z buffer algorithm processing unit (5) or the comparison logical operation processing unit (5) while interpolating each point of the primitive data in the designated area in each direction of x, y, z 6) is supplied with (x, y, z) data, and the drawing memory (4) is supplied with (x, y) data.

In the Z buffer algorithm processing section (5),
Since the Z value for each (x, y) data is stored in the Z buffer, the pixel data (x, y, z1) is compared with (x, y, z0) currently stored in the Z buffer. , 0 ≦ z1 ≦ z0
In the state of, the write enable signal is output to display (x, y, z1), and z1 is set in the Z buffer as a new z0. Conversely, when z0 <z1, the write enable signal is not output. Therefore, by sequentially updating the z0 value using the Z buffer algorithm processing unit (5),
Hidden surface treatment can be performed.

Further, in the comparison logical operation processing section (6), since the section data (x, y, z0) defining the section is stored in advance in the sectioning buffer, the pixel data (x, y, z1) is stored. Compare with cross-section data (x, y, z0) and
In the case of ≤z0≤z1, the write enable signal is output to display (x, y, z1), and conversely, in the case of z1 <z0, the write enable signal is not output. Therefore, the cross-section processing can be performed using the comparison logical operation processing unit (6).

The AND gate (8) writes only when the write enable signal output from the Z buffer algorithm processing unit (5) and the write enable signal output from the comparison logic operation processing unit (6) are both output. Since the permission signal is supplied to the drawing memory (4), the drawing processor (3)
The pixel data output from is written in the drawing memory (4).

After that, by supplying the pixel data stored in the drawing memory (4) to the monitor (7), it is possible to display a cross-sectional view which has been subjected to the hidden surface treatment and the cross-section treatment with a certain degree of accuracy.

The cross-section data stored in advance in the sectioning buffer is not limited to single plane data, and may be any free-form surface, and regardless of the cross-section data. Since it is only necessary to perform the same comparison logic operation, cross-section processing can be easily performed. That is, in the conventional cross-section processing,
Since the clipping process needs to be performed by the clip processor, the process can be easily performed in the case of a single plane where the z value is constant, but the process becomes significantly complicated in the case of a free-form surface or the like. Compared with the above, there is an advantage that the processing can be greatly simplified and the cross-section processing having a significantly high degree of freedom can be performed.

Further, since the cross-section processing can be performed in parallel with the drawing process, it is possible to completely eliminate the processing of feeding back the clipped data to the clip processor, and the z values of all pixel data are positive. If you know, z and
By diversion to direction clipping, the load on the clip processor can be reduced only in the x and y directions.

<Effects of the Invention> As described above, according to the present invention, cross-section processing with a certain degree of accuracy is possible only by performing a simple comparison logical operation using a sectioning buffer, and the system configuration can be simplified and various The unique effect that the cross-section display with a certain degree of accuracy based on the cut surface can be easily performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a sectional view drawing apparatus of the present invention, and FIG. 2 is a block diagram showing a conventional example. (3) …… Drawing processor, (4) …… Drawing memory, (5) …… Z buffer algorithm processing section, (6) ……
Comparison logic operation processing unit, (8) ... AND gate

Claims (2)

[Claims] 1. A three-dimensional graphic display device for transmitting pixel data to be drawn from a drawing processor to a drawing memory and displaying a three-dimensional figure on a display based on the contents of the drawing memory. Corresponds to the z value included in the output pixel data and the x and y values included in the pixel data output from the drawing processor, of the z values written to the Z buffer before the processing of the corresponding pixel data. Z value included in the pixel data
It is determined whether or not the value is in front, and the z value written in the Z buffer is updated with the z value included in the pixel data, provided that the z value included in the pixel data is in front. Z buffer algorithm processing means, a sectioning buffer that holds a Z value that defines a section, a z value included in pixel data output from the drawing processor, and a section that is written in advance in the sectioning buffer. Of z values, z corresponding to x, y values included in pixel data output from the drawing processor
The z value included in the pixel data is forwarded by the comparison logical operation processing means for comparing the magnitude with the value to determine whether or not the z value included in the pixel data is on the back side. To the drawing memory in response to the comparison result signal indicating that the z value included in the pixel data is on the back side is output from the comparison logic operation processing means. And a writing control unit for permitting writing of pixel data. 2. The cross sectional drawing drawing apparatus according to claim 1, wherein the z value preliminarily written in the sectioning buffer and defining the cross section is the z value defining the free-form surface.