Question

我正在尝试实现这一点：来自https://docs.google.com/viewer?url=http://www.tinaja.com/glib/bezdist.pdf&pli=1

以下BASIC程序使用查找距离的方法。该程序还搜索点和之间的最小平方距离曲线。

REM BEZIER.BAS JIM 20DEC92 12:37
DATA 2,3,5,8,8,14,11,17,14,17,16,15,18,11,-1
DATA 2,10,5,12,8,11,11,8,14,6,17,5,19,10,-1
DATA 2,5,5,7,8,8,12,12,13,14,12,17,10,18,8,17,7,14,8,12,12,8,15,7,18,5,-1
OPEN "BEZIER.OUT" FOR OUTPUT AS #1
OPEN "BEZ.ps" FOR OUTPUT AS #2
CLS
psscale = 20
FOR example% = 1 TO 3
REDIM rawdata(32)
FOR I% = 0 TO 32
READ rawdata(I%)
IF rawdata(I%) < 0! THEN EXIT FOR
NEXT I%
n% = I% - 1
PRINT "Example "; example%; (n% + 1) \ 2; " points"
PRINT #1, ""
PRINT #1, "Example "; example%; (n% + 1) \ 2; " points"
PRINT #1, " #
x
y"
J% = 0
FOR I% = 0 TO n% STEP 2
J% = J% + 1
PRINT #1, USING "### ####.### ####.###"; J%; rawdata(I%); rawdata(I% + 1)
LPRINT USING "####.### ####.### 3 0 360 arc fill"; rawdata(I%) * psscale; rawdata(I% + 1) * psscale
PRINT #2, USING "####.### ####.### 3 0 360 arc fill"; rawdata(I%) * psscale; rawdata(I% + 1) * psscale
NEXT I%
x0 = rawdata(0)
y0 = rawdata(1)
x1 = rawdata(2)
y1 = rawdata(3)
x2 = rawdata(n% - 3)
y2 = rawdata(n% - 2)
x3 = rawdata(n% - 1)
y3 = rawdata(n%)
IF example% = 3 THEN
’special guess for loop
x1 = 8 * x1 - 7 * x0
y1 = 8 * y1 - 7 * y0
x2 = 8 * x2 - 7 * x3
y2 = 8 * y2 - 7 * y3
ELSE
x1 = 2 * x1 - x0
y1 = 2 * y1 - y0
x2 = 2 * x2 - x3
y2 = 2 * y2 - y3
END IF
GOSUB distance
LPRINT ".1 setlinewidth"
PRINT #2, ".1 setlinewidth"
GOSUB curveto
e1 = totalerror
FOR Retry% = 1 TO 6
PRINT
PRINT "Retry "; Retry%
PRINT #1, "Retry "; Retry%
PRINT #1, " x1
y1
x2
y2
error"
e3 = .5

x1a = x1
DO
x1 = x1 + (x1 - x0) * e3
GOSUB distance
e2 = totalerror
IF e2 = e1 THEN
EXIT DO
ELSEIF e2 > e1 THEN
x1 = x1a
e3 = -e3 / 3
IF ABS(e3) < .001 THEN EXIT DO
ELSE
e1 = e2
x1a = x1
END IF
LOOP
e3 = .5
y1a = y1
DO
y1 = y1 + (y1 - y0) * e3
GOSUB distance
e2 = totalerror
IF e2 = e1 THEN
EXIT DO
ELSEIF e2 > e1 THEN
y1 = y1a
e3 = -e3 / 3
IF ABS(e3) < .01 THEN EXIT DO
ELSE
e1 = e2
y1a = y1
END IF
LOOP
e3 = .5
x2a = x2
DO
x2 = x2 + (x2 - x3) * e3
GOSUB distance
e2 = totalerror
IF e2 = e1 THEN
EXIT DO
ELSEIF e2 > e1 THEN
x2 = x2a
e3 = -e3 / 3
IF ABS(e3) < .01 THEN EXIT DO
ELSE
e1 = e2
x2a = x2
END IF
LOOP
e3 = .5
y2a = y2
DO
y2 = y2 + (y2 - y3) * e3
GOSUB distance
e2 = totalerror
IF e2 = e1 THEN
EXIT DO
ELSEIF e2 > e1 THEN
y2 = y2a
e3 = -e3 / 3
IF ABS(e3) < .01 THEN EXIT DO

ELSE
e1 = e2
y2a = y2
END IF
LOOP
IF Retry% = 6 THEN
LPRINT "1 setlinewidth"
PRINT #2, "1 setlinewidth"
END IF
GOSUB curveto
NEXT Retry%
LPRINT "100 200 translate"
PRINT #2, "100 200 translate"
NEXT example%
LPRINT "showpage"
PRINT #2, "showpage"
CLOSE #1
CLOSE #2
END
’
Bezier:
x = a0 + u * (a1 + u * (a2 + u * a3))
y = b0 + u * (b1 + u * (b2 + u * b3))
dx4 = x - x4: dy4 = y - y4
dx = a1 + u * (2 * a2 + u * 3 * a3)
dy = b1 + u * (2 * b2 + u * 3 * b3)
z = dx * dx4 + dy * dy4
s = dx4 * dx4 + dy4 * dy4
RETURN
’
distance:
totalerror = 0!
a3 = (x3 - x0 + 3 * (x1 - x2)) / 8
b3 = (y3 - y0 + 3 * (y1 - y2)) / 8
a2 = (x3 + x0 - x1 - x2) * 3 / 8
b2 = (y3 + y0 - y1 - y2) * 3 / 8
a1 = (x3 - x0) / 2 - a3
b1 = (y3 - y0) / 2 - b3
a0 = (x3 + x0) / 2 - a2
b0 = (y3 + y0) / 2 - b2
FOR I% = 2 TO n% - 2 STEP 2
x4 = rawdata(I%)
y4 = rawdata(I% + 1)
stepsize = 2 / (n% + 1)
FOR u = -1! TO 1.01 STEP stepsize
GOSUB Bezier
IF s = 0! THEN u1 = u: z1 = z: s1 = s: EXIT FOR
IF u = -1! THEN u1 = u: z1 = z: s1 = s
IF s < s1 THEN u1 = u: z1 = z: s1 = s
NEXT u
IF s1 <> 0! THEN
u = u1 + stepsize
IF u > 1! THEN u = 1! - stepsize
DO
GOSUB Bezier
IF s = 0! THEN EXIT DO
IF z = 0! THEN EXIT DO
u2 = u
z2 = z
temp = z2 - z1
IF temp <> 0! THEN
u = (z2 * u1 - z1 * u2) / temp

ELSE
u = (u1 + u2) / 2!
END IF
IF u > 1! THEN
u = 1!
ELSEIF u < -1! THEN
u = -1!
END IF
IF ABS(u - u2) < .0001 THEN EXIT DO
u1 = u2
z1 = z2
LOOP
END IF
totalerror = totalerror + s
NEXT I%
PRINT totalerror;
PRINT #1, USING "####.### ####.### ####.### ####.### ######.###"; x1; y1; x2; y2; totalerror
RETURN
’
curveto:
LPRINT USING "####.### ####.### moveto"; x0 * psscale; y0 * psscale
PRINT #2, USING "####.### ####.### moveto"; x0 * psscale; y0 * psscale
F$ = "####.### ####.### ####.### ####.### ####.### ####.### curveto stroke"
LPRINT USING F$; x1 * psscale; y1 * psscale; x2 * psscale; y2 * psscale; x3 * psscale; y3 * psscale
PRINT #2, USING F$; x1 * psscale; y1 * psscale; x2 * psscale; y2 * psscale; x3 * psscale; y3 * psscale
RETURN

我想用c ++实现它，因为我试图让我的算法最适合来自点的beziers。

在伪代码或c / c ++中，上述内容会是什么样的？感谢

Answer 1

这里最好的方法是逐位拆分代码并进行轻微的重构，直到它处于可用状态。首先可以将数据更改为全局变量。

然后开始获取代码的小块并将它们转换为函数。起初他们只会使用一堆全局数据。当您将这些部分重写为C ++时，事情会变得更加清晰。

一旦你在功能上构建了大部分代码，那么你就可以开始重构变量了。目标是删除所有全局非常量数据，并使所有工作数据都是本地数据。 const值可以保留命名空间级别的初始化数据。

最后，一旦基于程序，您就可以决定是否值得将工作封装到对象和方法中。根据程序需要维护多长时间，对数据和方法进行分组可能是一个很好的长期步骤。

这看起来像伪代码是什么？

1 个答案: