JPH0683972A - Curve generating device - Google Patents

Abstract

PURPOSE:To speed up the geometrical processing in a three dimensional Bezier curve interpolating control points with a smooth curve for four control pints given on the curve. CONSTITUTION:The distance discrimination between the control point and the calculated point is performed in a comparator 7 every time when the point on the three-dimensional Bezier curve is calculated for the given four control points. During the discrimination by the comparator 7, an arithmetic unit 4 starts recursive processing in advance without waiting for the discrimination result. It continues the processing as it is when the discrimination by the comparator 7 does not meet the condition, and if it meets the condition, the arithmetic units 4 and a shifter 5 are cleared and a pointer control circuit 8 restarts the processing for the control point of a pointer 3 which is newly set. Thus, the waiting time of the arithmetic unit 4 is reduced and the generation of the free curve is speeded up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curve generating device for generating a free curve from a given control point sequence in a graphics related device for outputting characters or figures to a display or a printer.

[0002]

2. Description of the Related Art In recent years, Japanese word processors and DTR (Des
With the commercialization of k Top Publishing, there is an increasing demand for character print quality.
In particular, in the DTP field, it is needless to say that the character quality is highly demanded, but there are also many demands for the character size and the type of the font, so that the outline font has been attracting attention in place of the bit map font. Also in the field of personal computers, WYSIWYG (What You See) allows you to match the characters displayed / printed on the display and the printer so that the printed image can be checked on the screen as it is.
Outline font technology is also drawing attention toward the realization of Is What You Get).

The outline font, which is also called "contour vector font", is a mathematical expression of the contour of a character pattern and paints between the contour lines (or in a closed loop) to generate a character. The mathematical formula used to express a curved portion by the outline of a character is generally a curve called a Bezier curve.

This Bezier curve is a curve that can be interpolated by a smooth curve between these control points when several control points are given, and the most widely used is the cubic Bezier curve. If a cubic Bezier curve is given four arbitrary control points, curve interpolation between the control points is possible. As described above, the free-form curve has an advantage that the amount of information defining the shape is very small and the character quality does not deteriorate even when the character is enlarged / reduced.

Next, a conventional Bezier curve algorithm will be described. Generally, an algorithm that obtains from the starting point of a curve is well known, but since division and multiplication need to be executed frequently, an algorithm using geometric processing is often used for speeding up. .

FIG. 3 shows a block diagram of a conventional curve generating device which is realized by dedicated hardware, and FIG. 4 shows a geometrical coordinate diagram for generating a cubic Bezier curve. In FIG.
Reference numerals 1 and 2 are RAMs for storing coordinate points, 3 is a pointer for storing the RAM address, and 4 is an R set by the pointer 3.
An arithmetic unit 5 for adding two pieces of AM data, and an arithmetic unit 4
The shifter that shifts the result of addition by 1 bit, 9 is the sequencer that controls the RAM, pointer, arithmetic unit, and shifter, 6 is the distance register that stores the distance value, and 7 is the shifter output value and four controls It is a comparator that compares the distance between the start point of the point and the value stored in the distance register 6. Each of the four control points A to D provided is a RAM.
It is stored in.

First, the midpoints E, F and G of the line segments AB, BC and CD formed by the four points in FIG. 4 are obtained. As for the middle point, the coordinate points stored in the RAMs 1 and 2 are transferred to the arithmetic unit 4 by the operation of the pointer 3, and the arithmetic unit 4 adds the coordinate values of the two control points. This operation result is the shifter 5
Input it to and halve it. The calculation result is stored in the RAMs 1 and 2 according to the sequencer 9.

Similarly, the midpoints H and I of the line segments EF and FG are obtained, and the midpoint J of the line segments H and I is obtained. This point J is 3
The next point is on the Bezier curve. Next, the points A, E, H, and J are set as control points, and the above-described processing is performed in the same manner to obtain a point Q on the next curve. After the points on the curve are obtained in this manner, the points on the Bezier curve can be obtained by repeatedly performing the recursive processing on the four new control points.

Another consideration in the generation of this Bezier curve is the replacement of control points. When the above process is repeated, the obtained point on the Bezier curve approaches the point A as much as possible. Therefore, it is necessary to terminate the processing when the distance to the point A is approached to a certain extent and change the processing to calculate the point at another location. That is, the distance value serving as the criterion is stored in the distance register 6, and the distance between the output value from the shifter 5 and the point A is compared with the value stored in the distance register 6. If the distance between the point A in FIG. 4 and the obtained point Q on the curve is smaller than the preset value of the distance register 6, the four target control points are set to the points J, I, and
The same process is repeated for G and D.

[0010]

As described above, the conventional free-form curve is generated by the dedicated hardware every time the point on the cubic Bezier curve obtained from the four control points is determined.
The distance between this point and the start points of the four control points is compared with the value stored in the distance register 6. As a result of the comparison, if it is larger than the distance register value, the point on the cubic Bezier curve is recursively obtained from the four control points given next. That is, in order to obtain the point on the cubic Bezier curve, the recursive process is repeatedly performed until the distance between the obtained point on the cubic Bezier curve and the start point becomes smaller than the value of the distance register 6. While the value in the distance register is being compared with the calculated distance between the point on the curve and the start point, the adder (4) is in a state of waiting for determination of the comparison result. That is, since the comparison operation is performed until the points on the curve converge to a certain value, the more the comparison operation is, the longer the waiting time of the arithmetic unit 4 is.

The object of the present invention is to solve these problems,
It is an object of the present invention to provide a curve generator that speeds up arithmetic processing.

[0012]

According to the structure of the present invention, the coordinates of the midpoint between control points are calculated from the coordinate values of a plurality of designated control points to perform curve interpolation in the vicinity of the control points. In a curve generating device for generating a plurality of storage points, a plurality of storage means for storing the plurality of control points and the plurality of the middle points by dividing them into some groups, pointers for storing addresses of these storage means, and each storage An arithmetic unit for adding the coordinate values of two predetermined points stored in the means, a shifter for storing the output value of the arithmetic unit in one of the storage means after 1-bit shift, and a predetermined distance value , A comparator for comparing the value of this register with the output value of the shifter, a pointer control circuit for controlling the operation of the pointer according to the comparison result of this comparator, and an output of the comparator. Characterized in that it comprises a sequencer for controlling the comparator and the shifter and the operation unit in accordance with the signal.

[0013]

The curve generator of the present invention is mainly used for the operation of the arithmetic unit during the period in which the distance between the calculated point on the curve and the start points of the four control points is compared with the value of the distance register. There is a difference. That is, at the same time as the comparison is performed by the comparator, the computing unit starts the computation of the four control points given next as the forward processing. The algorithm of the geometrical cubic Bezier curve divides the trapezoid given by the four control points at first every time one point on the curve is calculated, and divides the trapezoid into two, and divides the trapezoid into two. Repeat the recursive process for the trapezoid. Then, the above-described processing is repeated until the calculated point on the curve approaches a certain distance from the start points of the first four control points. Therefore, the pointers of the four control points are not largely changed until the value of the distance register becomes larger as a result of the comparison, and the comparison operation and the operation of the operation unit can be processed in parallel and high-speed processing can be performed.

[0014]

1 is a block diagram of a first embodiment of the present invention. In this embodiment, a pointer control circuit 8 is added to the conventional example shown in FIG. As in FIG. 3, the addresses of the two RAMs 1 and 2 that store the plurality of control points and the plurality of midpoints in two groups are stored in the pointer 3. The coordinate values of two predetermined points stored in the two RAMs 1 and 2 are added by the calculator 4. The output value of the arithmetic unit 4 is shifted by 1 bit by the shifter and stored in one of the two RAMs 1 and 2. The distance register 6 stores a preset distance value, and the comparator 7 compares the output value of the shifter 5 with the value of the register 6. The pointer control circuit 8 controls the pointer operation according to the comparison result of the comparator 7. Further, according to the output signal of the comparator 7, the arithmetic unit 5, the shifter 6 and the comparator 7
And the sequencer 9 controls.

In this embodiment, coordinate values of four points are input and points on the cubic Bezier curve are generated from the side closer to the starting point. Sampling of a straight line is performed until the distance between adjacent points becomes smaller than the predetermined distance in both the X coordinate and the Y coordinate. The coordinate value representation is a 16-bit fixed point, and the X-coordinate value and the Y-coordinate value have the hardware configuration shown in FIG. However, since the processing sequence is the same, the sequencer 9, the pointer control circuit 8, and the pointer 3 can be shared.

First, as shown in FIG. 4, the respective midpoints of line segments AB, BC and CD which are composed of four control points A, B, C and D stored in the RAM are obtained. The pointer 3 points to the coordinate points A and B according to the pointer control circuit 8, reads these coordinate points from the RAMs 1 and 2, transfers them to the arithmetic unit 4, and adds two coordinates by a control signal from the sequencer 9. Next, according to the control signal from the sequencer 9, the shifter 5 performs a 1-bit shift operation on the result in the arithmetic unit 4, and the pointer 3 points the coordinate point B and the coordinate point C according to the pointer control circuit 8. Then, the coordinates are read from the RAM and transferred to the arithmetic unit 4, and the two coordinates are added by the control signal from the sequencer 9.

By repeating such processing, the midpoints E, F and G of the line segments AB, BC and CD are obtained, the end points H and I of the line segments EF and FG are then obtained, and the line segment HI is further obtained. Midpoint J
And the point J becomes a point on the cubic curve. When this point J is calculated, the output of the shifter 5 is stored in the RAM, and the output point J of the shifter 5 is generated by the control signal of the sequencer 9.
The coordinates are stored in the comparator 7.

In parallel with this operation, the first four control points A, B, C, D are formed into two trapezoids of points A, E, H, J and points J, I, G, D around the point J. Divide and similarly determine the midpoints for the four control points A, E, H, and J, and start the arithmetic processing in parallel to obtain the point Q shown in FIG. Calculate points).

The comparator 7 compares the distance between the points A and J with the preset value of the distance register 6. In this case, since the distance between the points A and J is still larger than the value of the distance register 6, the control signal is sent to the pointer control circuit 8 so that the recursive process is repeated as it is. Also, the comparator 7
The result in step 1 is also sent to the sequencer 9, and control is performed so that recursive processing is repeated.

During this time, the arithmetic unit 4 and the shifter 5 simultaneously determine the midpoint of the line segment AE. When the point Q on the cubic Bezier curve is obtained from the trapezoids A, E, H, and J, the comparison is performed by the comparator 7 similarly to the point J, and the following four control points A,
The recursive process for finding the middle point for K, O and Q is performed by the arithmetic unit 4
Start with. In the comparator 7, if the value is smaller than the preset value of the distance register 6, the control points A, K, O, Q
It is not necessary to obtain the midpoints for, and next, it is necessary to obtain the midpoints for the four control points J, I, G, and D.

Therefore, from the comparator 7, the arithmetic unit 4 and the shifter 5
Is sent to the sequencer 9, and a control signal is sent to the pointer control circuit 8 so that the pointer 3 points the coordinate values of the four new control points J, I, G and D. By repeating the above operation, it is possible to interpolate between the points A and D at the first four control points A, B, C, and D according to a cubic Bezier curve.

FIG. 2 is a block diagram of the second embodiment of the present invention. In this embodiment, four RAMs, two arithmetic units and two shifters are prepared for the first embodiment to further increase the speed. In contrast to FIG. 1, RAMs 10 and 11 and arithmetic units are provided. 12 and a shifter 13 are added. In order to obtain one point on the cubic Bezier curve from four control points and perform interpolation processing, it is necessary to obtain the middle point seven times, and the waiting time of the computing unit is reduced with one computing unit and one shifter. It will be faster. Other processes are the same as those in the first embodiment.

Four RAMs 1, 2, 10, 1 for storing a plurality of control points and a plurality of midpoints by dividing them into four groups
One address is stored in the pointer 3. These four R
The coordinate values of the predetermined two points stored in the AM are calculated by the arithmetic units 4 and 12
Are added, and the output values of the arithmetic units 4 and 12 are shifted by 1 bit by the shifters 5 and 13, and the four RAMs 1, 2, 1
It is stored in either 0 or 11. The comparator 7 compares the output values of the shifters 5 and 13 with the register 6 and the value, and the pointer control circuit 8 controls the pointer operation according to the comparison result of the comparator 7.

[0024]

As described above, according to the present invention, 4
The point on the cubic Bezier curve is calculated from the three control points and compared with the value in the distance register.
By starting the calculation of the points on the next Bezier curve in parallel, the waiting time in the arithmetic unit is reduced and the speed can be increased as compared with the conventional example. Further, by increasing the number of arithmetic units and shifters, it is possible to further increase the speed. Further, according to the present invention, since the distance between the four control points increases when the character is enlarged, the number of times of recursive processing for obtaining a point on the cubic Bezier curve increases, and the larger the character, the considerably larger than the conventional example. It becomes possible to realize high-speed processing.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional curve generator.

FIG. 4 is a coordinate diagram illustrating a geometric algorithm of a cubic Bezier curve.

[Explanation of symbols]

 1,2,10,11 RAM for storing coordinates and midpoint 3 Pointer for pointing to RAM address 4,12 Arithmetic unit 5,13 Shifter 6 Register for storing value to be compared 7 Comparator 8 Pointer control circuit 9 Sequencer

Claims (1)

[Claims] 1. A curve generator for generating a curve by interpolating a curve in the vicinity of the control points by calculating coordinates of a midpoint between the control points from coordinate values of a plurality of designated control points. A plurality of storage means for storing the control points and the plurality of the midpoints by dividing them into several groups;
A pointer for storing the address of these storage means, an arithmetic unit for adding the coordinate values of the predetermined two points stored in each of the storage means, and an output value of this arithmetic unit after shifting one bit by some of the storage means. , A register for storing a predetermined distance value, a comparator for comparing the value of this register with the output value of the shifter, and the operation of the pointer according to the comparison result of this comparator. And a sequencer for controlling the arithmetic unit, the shifter, and the comparator according to an output signal of the comparator.