JPS63143675A - Picking system for straight line - Google Patents

Abstract

PURPOSE:To remove dividing operation from picking processing by deciding final pick by means of four corner points obtained by a four-corner point forming means and a discriminant for deciding whether four corner points are divided into two parts by a straight line passing both the end points of a straight line to be picked up. CONSTITUTION:A detailed pick inspecting part 120 is provided with a four- corner point forming means 121 for finding out four corners of a picking frame, a decision forming means 122 for forming the discriminant whether the four corner points are divided into two parts by a straight line passing both the end points of the straight line to be picked up and a final decision means 123 for deciding 136 the final pick by means of the obtained four corner points and the decision formula 135. Namely, the inspection part 120 uses the straight line to be picked up as a reference and decides the final pick by the means 123 by means of the four corner points of the picking frame obtained by the means 121 and the decision formula 135 obtained by the means 122. Consequently, the calculation of an intersecting point, i.e., dividing operation, can be omitted and the number of times of operation can be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a straight line picking process in the field of computer graphics, that is, a straight line picking method in which straight lines within a certain frame are extracted by calculation. be.

[Conventional technology]

In conventional pick processing, drawing processing techniques are applied to draw the shapes to be picked in order of priority, and when the first shape to be drawn within the pick frame is found, this shape is selected as the picked shape. Extracted and finished the pick process. However, for pick processing that requires interactive responses, a method that requires processing time equivalent to drawing numerous figures is not appropriate, and a faster pick processing method has been desired.

On the other hand, picking processing is required for drawing in the graphics field, where most figures are usually drawn by linear approximation.

Therefore, regarding the straight line picking method, for example, a calculation based picking method using the straight line clipping method (PP, 138-145) described in [Graphic processing engineering using computer displays (Nikkan Koshinkaisha) J] written by Fujio Yamaguchi. Since this can be easily inferred, this straight line clipping method will be cited as a conventional technique.

FIG. 4 is a clipping flowchart showing the flow of this linear clipping method. In the figure, 100 is an input data section necessary for clipping processing by calculation, 110 is a pick preliminary inspection section that performs a rough pick inspection based on data input manually from this input data section 100, and 12
0 is a pick detailed inspection section that performs a more detailed inspection on straight lines that cannot be determined by the pick preliminary inspection section 110 alone. This will be explained in detail below.

Both end points 101 of the straight line (L) to be clipped inputted from the input data section 100 are (x6.yo) and (X+
, 3'+), and the four straight lines 102 of the clip frame that are also input from the input data section 100 are x-XL, X=Xa,
)'=)'a+3'=3'y. In order to easily determine to which region the end point (x, y) of the straight line (I7) belongs among the nine regions divided by the four straight lines 102 of the clipping frame, the following vector is obtained.

(yT 'j23' Vs, x* x, x x
t) --(1) As a result of calculation of equation (1), if the sign of each term is positive, it is set to 0, and if it is negative, it is set to 1, and a 4-bit code is generated. The means for performing this operation is the code generation means 111.

FIG. 5 is a list of codes showing codes in nine areas divided by four straight lines 102 of the clipping frame.

Here, both end points 101 of the straight line (L) not shown
If the signs of (Xo, yo) and (X+, y+) are C6 and C5, the following is clear from FIG.

(+) If Go =C+ =0000, then (x,,y
a) and (xt, y+) both exist within the frame of the clip.

Therefore, the straight line (L) exists completely within the frame of the clip.

(II) If Go AND C1≠0000, then (X
O, )'O) and (xt, y+) are both clip frame 4
Regarding at least one of the straight lines 102, it exists in an area outside the clipping frame of the two areas divided by the straight line. Therefore, the straight line (L) exists completely outside the clip frame.

For a straight line that falls under either of the two-line properties (i) and (ii), it can be determined whether or not the target straight line will be clipped just by this series of processing. The means for performing this operation is the code verification means 112, and the code verification means 112 and the code generation means 111
The determined straight line 132 is a straight line that can be determined only by the following steps.

The operations up to this point are the operations of each means in the pick preliminary inspection section 110, and then the pick detailed inspection section 120
The operation will be explained below.

Since at least one end point of a straight line that does not fall under either of the two-line properties (i) and (ii) must exist outside the clip frame, the end point outside the clip frame must be (x@,
yo). For this purpose, the following process may be performed.

If falcO-0000, (Xo, yo) and (xl
.

y+).

(blco　”　If it is not OOOO, do nothing.

Naturally, when (x6.yo) and (X+, y+) are exchanged, the code C6 and CI are also exchanged.

Next, based on 00, it is determined in which region the end point (xo, yo) exists with respect to each of the four straight lines 102 of the clipping frame. The following things are clear from Figure 5.

(i) If 'Co AND OOO1≠0000,
Xo<xL.

(ii) If 'Co AND OO10≠0000, then XH<Xo.

(iii)'CoAND If 0100≠0000, then yo<yB.

(iv) 'Above three conditions (i)', (ii)' and (ii)
i) If it is other than ', yTkuyo.

In each of the four conditions (i), (ii)', (iii)' and (iv)', the target straight line (for example, x=x in the case of condition (i)) and the straight line ( Find the intersection point with L) and the sign of that intersection point and newly calculate (Xo, yo
) and C8. The new point (xo, yo) is calculated as follows.

(i)'''In the case of the above condition (i)°, (xo, yo)=(xt, yo+(y+-yo)*(X
L -xo)/(x+-Xo))(ii)''In the case of the above condition (ii)', (xo, Vo); (xi, yo+(
y+-yo)* (xll-xo)/(X+-xo)
) (iii) In the case of ``the above condition (iii)',
(xo, yo)−(χo+(x+−xo)*(ye
-yo)/(y+-yo)+yg)(iv)l
+ In the case of the above condition (iv)'', (xo, yo) - (
xo+ (ni+-Xo) * (VT -yo)/(y
+-yo)+yt) The straight line (L
) and the new endpoints (xo, yo) and (X+, y+) of The target straight line can be clipped only by multiplication and division, and several additions, subtractions, and comparisons.

[Problem that the invention seeks to solve]

When considering a straight line picking method using this straight line clipping method, for a straight line that falls under either of the two-line properties (i) or (ii) above, the target straight line may or may not be picked. It can be easily determined whether However, for a straight line that does not fall under either of the above-mentioned two-line properties (i) or (ii), at least one multiplication and division and several additions and subtractions are required for one intersection calculation.

In the worst case, as many as four multiplications and divisions are required.

In particular, division operations require an enormous amount of calculation time, and generally, the result of division is an infinite decimal number, which cannot be accommodated within a finite number of digits, and accuracy cannot be guaranteed.

This invention has been made to solve this problem, and eliminates the division operation from the pick process by eliminating the need for division operations for straight lines that cannot be easily determined by the pick pre-inspection section alone. The purpose is to obtain a high-speed and highly accurate straight line picking method by reducing the .

[Means for solving problems]

The pick detail inspection unit in the straight line pick method according to the present invention includes four corner point generation means for calculating four corner points of the pick frame;
A discriminant generating means for generating a discriminant for determining whether or not the four corner points are bisected by a straight line passing through both end points of the straight line to be picked; and final determination means for making a final pick determination.

[Effect]

The pick detail inspection section of this invention, like the pick preliminary inspection section, makes judgments based on the four straight lines of the pick frame in the conventional method, so intersection calculations are essential and division operations are required. The final discriminator uses the four corner points of the pick frame obtained by the four corner point generating means and the discriminant obtained by the discriminant generating means to make a discrimination using the straight line as a reference, so the intersection point calculation, that is, the division operation is performed. This is not necessary and the number of calculations is reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 100 is an input data section necessary for pick processing by calculation, and 110 is a rough calculation based on the data input from this input data section 100. A pick preliminary inspection section 120 inspects the pick, a pick detailed inspection section 120 performs a more detailed inspection on straight lines that cannot be determined by the pick preliminary inspection section 110 alone, and 130 indicates the pick detailed inspection section 120 and the pick. This is an output data section obtained by the preliminary inspection section 110. 101 are both end points of a straight line to be picked, and 102 are four straight lines of the pick frame. 111 is a code generating means for generating a code necessary for performing a big preliminary inspection based on both end points 101 of the straight line to be picked and the four straight lines 102 of the big frame, and 131 is a code generated by this code generating means 111. The code is 11
Reference numeral 2 denotes a sign testing means for testing the code 131 in order to perform a BIC preliminary test, 132 a straight line determined by the sign testing means 112, and 133 the sign testing means 11.
It is a straight line that cannot be determined with only 2. 121 is a four corner point generating means for generating four corner points of a pick frame necessary for performing a pick detailed inspection on this undeterminable straight line 133;
134 are the four corner points of the pick frame generated by the four corner point generating means 121; 122 is a discriminant generating means for generating a discriminant necessary for performing a big detailed inspection;
5 is a discriminant generated by this discriminant generating means 122, 123 is a final determining means for making a final big judgment based on this discriminant 135 and the four corner points 134 of the pick frame, and 136 is a final determining means This is the final big decision made by this final decision means 123.

Next, the operation will be explained. Data 101 and 102 in the input data section 100, means 111 and 112 in the pick preliminary inspection section 110, and further the reference numeral 1
319 determined straight line 132, undetermined straight line 133
is exactly the same as the prior art. The pick preliminary inspection section 1
The operation of the big detail inspection unit 120 regarding the straight line 133, which cannot be determined using only the line 10, will be explained.

4 straight lines 10 of the pick frame for detailed pick inspection
Find the following four points from 2.

(XL, yt)l(XR,VT)l(XL, y
The four points given by the formula (2) are the four corner points 134 of the pick frame, and the means for performing this operation is the four corner point generating means 121. Also,
Considering a straight line passing through both end points (Xo, yo) and (xl, yt) of the undeterminable straight line 133, the following discriminant is introduced.

F(x,y)=(y-yo)*(xt-xo)-(yt
-yo)*(x-xo) ---(31 The discriminant F (x, y) given by equation (3) is the discriminant 135
The means for performing this operation is the discriminant generating means 122. Four corner points 134 of the pick frame (four points in equation (2))
The final determination means 123 determines whether or not is divided into two by the discriminant 135 ((31)), thereby executing the big processing.

To do this, it is sufficient to substitute each point in (2) 2 into equation (3) and check the sign in each equation. By substituting each point of equation (2) into equation (3), the following equation is obtained.

F(XL-yt)-(VT-yo)*(xl-xo)
-(yt-yo) umbrella (xt-xo)・-(4) FCx*, y7)=(yt-yo)*(xt-xo
)-(yt-yo)* (XR-xo)--(5) F(XLI VB)-(Vs-Vo)"(xt-xo
)−(yt−Vo)” (XL −Xo)−・−(6) P(XRI yll)=(yn −yo)*(xt−x
o)-(yt-yo)* (XR-3[0) Figure 2 is
It is a discriminant and four corner point relationship diagram showing the relationship between the discriminant 135 and the four corner points 134 of the pick frame. From Figure 2,
The following is clear:

(1) (41-(71) If even one of the formulas becomes zero, the straight line will be surprised.

(n) If at least one of the equations (41 to (7)) has an opposite sign, a straight line is picked.

(III) If all of equations (41 to (7)) have the same sign, no straight line will be picked.

If the conditions of the three-stripe properties (I), (ff), and (Ill) are determined, and the final pick is determined for the undeterminable straight line 133, four multiplications, several subtractions, and Pick processing can be performed by comparison operations. This is because equations (4) to (7) each contain two identical terms.

With the method described above, the pick detail inspection section 120 does not need a division operation, and can realize a high-speed and highly accurate straight line picking method. When the pick processing is implemented in hardware, the hardware configuration becomes simple and a product can be obtained at a low price.

However, since multiplication generally requires more calculation time than addition/subtraction and comparison operations, we will consider ways to further reduce the number of multiplications. FIG. 3 is a final judgment flowchart showing the detailed operation of the final judgment means 123, and 301 is a parallel line judgment unit that makes a judgment when the straight line to be cut is parallel to the X-axis or the y-axis. , 302 is a non-parallel line determining unit that determines when a straight line to be picked is not parallel to either the X axis or the y axis. Both end points (x 6. y o) and (x
l, yt), the following is clear.

If (r)'xl = Xo, the straight line to be picked is a straight line parallel to the y-axis, and if xL≦xo≦xR is satisfied, the straight line is picked; otherwise, the straight line is not picked.

(II)'y+ -y. Then, the straight line to be picked is a straight line parallel to the X axis, and if yB≦y0≦yT is satisfied, the straight line is picked; otherwise, the straight line is not picked.

The parallel line determining unit 30 is a block that performs conditional determination of the two-line property (T) and (■)′ and determines the final pick.
It is 1. Said two-row (I)'' and (old).

For straight lines that do not fall under any of the following, the final pick determination process differs depending on the slope of the straight line, so the following process is applied to make the determination easy.

(A) If XO<XI, do nothing.

(B) If Xo < xl, then (Xo, yo) and (X
I, Y+).

As a result of this processing, the following equation always holds.

X + X o > 0
-(81) A straight line that does not meet either of the two conditions (I) and (old) has a certain non-zero finite slope, and the pick determination process differs depending on whether this slope is positive or negative. The sign of the slope is (XI Xo) and (yt
Although it is determined by determining the sign of (yt yo), since (XI xo>o) always holds true from equation (8), the sign of the slope is determined by the sign of (yt yo).

Next, a pick determination process for a straight line with a positive slope will be described, but a pick determination process for a straight line with a negative slope can be performed in the same manner. The following points are clear from Figure 2.

[For straight lines with positive slope]

(1) If F (XL, yB) = O, the straight line is picked.

(II)” F (XL, yn) > O and F
If (xR, ytr)≦0, the straight line is picked.

(Iff)” If F (XL, yll) < 0 and F (XL, yT) ≧0, the straight line is picked.

(IV) “Said three-stage (I)”, (II)” and (II)
Straight lines other than "I)" are not picked.

The above four conditions (1)”, (■)゛, (■)°” and (■
The non-parallel line determining unit 302 is a block that performs conditional determination of ) and final pick determination.

Further, the process in the non-parallel line determining unit 302 and the parallel line determining unit 301 is executed, and the undeterminable straight line 1
The means for making the final judgment regarding 33 is the final judgment means 1.
23, resulting in a final pick decision 136.

Next, consider the number of multiplications. The parallel line determination section 3
01 does not require multiplication, so the calculation including multiplication for a straight line with a positive slope in the non-parallel line determining section 302 will be shown below.

(I)''In the case of the above condition (■)'', P(XL, ytr)=(yi -yo)*(x+-
xo)-(yt-yo)*(xt-xo)(II)
In the case of ``'condition (II)'', F(Niri, 31f
)=(yll −Vo)*(I−Xo)−(yt−
yo) * (xt - xo) - α [ F (XR, ym ) = (ym - yo) * (x+ - xo
)−(yt−yo)*(xll−xo)−(rsu(■)゛゛For the above condition (III),
yn )=(yll −yo)”(x+−xo)−(
yt-yo)*(xt-xo)-, (JF(XL, yt)=(yt-yo)*(x+-x
o)-(yt-yo)* (xt-xo)--tt3
In the case of “the above condition (IV)”, the above condition (IV)
II)'' or (III) Same as ''.

In the four conditions (1)'' to (IV)'', the number of multiplications is three in all cases except for the two in condition (1)''.This is because 00) and equation (B) Or (7Q and (I
This is because the equation 3) contains one identical term.

Finally, we will summarize the amount of calculations required throughout the straight line pick process. The amount of calculations required by the pick pre-inspection unit 110 is exactly the same as in the prior art, only a few subtraction and comparison operations. Meanwhile, the amount of calculations required by the pick detail inspection unit 120 is at most three multiplications, several subtractions, and comparison operations. In the conventional method, the pick detail inspection unit 120 requires at least one multiplication and division, and in the worst case, as many as four multiplications and divisions, but the present method eliminates the need for division operations. Become. Also, regarding the calculation time required for straight line pick processing, assuming that the calculation time for division is approximately twice the calculation time for multiplication, and the total calculation time required for pick processing is approximately equal to the calculation time for multiplication and division. , while the conventional method required calculation time equivalent to at least 3 multiplications, 7.5 times on average, and as many as 12 times in the worst case, the present method requires calculation time equivalent to at most 3 multiplications. Straight line pick processing can be performed using only calculation time.

(Effects of the Invention) As described above, according to the present invention, the pick detail inspection section includes the four corner point generation means for calculating the four corner points of the pick frame, and the four corner point generation means for calculating the four corner points of the pick frame.
A discriminant generation means that generates a discriminant for determining whether a corner point is parted by a straight line passing through both end points of the straight line to be picked, and a final By having a final judgment means for making a pick judgment, it is possible to eliminate the need for division operations, which were necessary in the conventional technology for detailed pick inspection, and to reduce the number of operations, resulting in high speed and accuracy. It is possible to pick high straight lines. Further, since the division operation is not required, when the straight line pick processing is implemented in hardware, the hardware configuration becomes simpler and the cost can be lowered.

[Brief explanation of the drawing]

Fig. 1 is a straight line picking procedure diagram showing an embodiment of the present invention, Fig. 2 is a discriminant and four corner point relationship diagram showing the relationship between the discriminant and the four corner points of the pick frame, and Fig. 3 is a diagram showing the relationship between the discriminant and the four corner points of the pick frame. Final judgment flowchart showing detailed operation in final judgment means of other embodiments, No. 4
Figure 5 is a clipping flowchart showing the method of the prior art.
The figure is a list of codes showing codes in nine areas divided by four straight lines of the crimp frame. In the figure, 100 is the input data section, 101 is both end points of the straight line to be picked, 102 is the 4 straight lines of the pick frame, 1
10 is a pick preliminary inspection section; 111 is a code generation means; 11
2 is a sign verification means, 120 is a pick detailed inspection unit, 121
are four corner point generation means, 122 is a discriminant generation means, 123 is a final judgment means, 130 is an output data section, 131 is a code,
132 is a determined straight line, 133 is a straight line that cannot be determined,
134 is the four corner points of the pick frame, 135 is a discriminant, and 136 is the final pick determination. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masu Oiwa M (and 2 others) = 21- Procedural amendment (voluntary) 1. Indication of the incident: Patent Application No. 61-289800 2,
Name of the invention Straight line pick method 3, Representative Moriya Shiki 5, Claims to be amended, Detailed description of the invention, Drawings column. 6. Contents of amendment (1) The scope of claims will be amended as shown in the attached sheet. (2) Specification page 12, line 11 r (XR, YT)-
-----(21J) [(X R, Y a )
−−−−−(2) Correct as J. (3) Correct the drawings, Figures 3 and 4 as shown in the attached sheet. Above 2, Claims (1) Both end points of the straight line to be picked and 4 of the pick frame
There is a pick preliminary inspection section that performs a pick preliminary inspection of the target straight line based on the straight line, and a pick detailed inspection section that performs a final pick detailed inspection on straight lines that cannot be determined by this preliminary inspection section alone. In the straight line pick method in which straight line pick processing is performed by Sf calculation, the pick detail inspection section includes four corner point generation means for determining four corner points of the pick frame. A discriminant generating means for generating a discriminant for determining whether or not the four corner points are parted by a straight line passing through both end points of the straight line to be picked; and final determination means for making a final pick determination. +21 The final determination means determines the pick by substituting each of the four corner points into a discriminant and checking the sign of each obtained discriminant. Straight pick method. (3) The final determination means includes a parallel line determination unit that examines the inclination of the straight line to be picked and determines if the straight line is parallel to the X axis or y axis corresponding to the four straight lines of the big frame;
2. The method for picking a straight line according to claim 1, further comprising a straight line pick plate that determines when the straight line is not parallel to either the axis or the y-axis.

Claims (3)

[Claims] (1) Both end points of the straight line to be picked and 4 of the pick frame
There is a pick preliminary inspection section that performs a pick preliminary inspection of the target straight line based on the straight line, and a pick detailed inspection section that performs a final pick detailed inspection on straight lines that cannot be determined by this preliminary inspection section alone. In the straight line picking method in which the straight line picking process is performed by calculation, the pick detail inspection section includes a four corner point generation means for calculating four corner points of the pick frame, and a four corner point generation means for determining the four corner points to be picked. A discriminant generating means that generates a discriminant to determine whether the straight line is bisected by a straight line passing through both end points, and a final pick determination using the four corner points and the discriminant obtained above. A straight line picking method characterized by comprising: a final determination means for performing a straight line pick method. (2) The final determination means determines the pick by substituting each of the four corner points into a discriminant and checking the sign of each obtained discriminant. Straight line pick method as described. (3) The final determination means includes a parallel line determination unit that examines the inclination of the straight line to be picked and determines if the straight line is parallel to the x-axis or y-axis corresponding to the four straight lines of the pick frame;
2. The straight line picking method according to claim 1, further comprising a parallel line determining unit that determines if the straight line is not parallel to either the axis or the y axis.