Description
PS11 Segmentation of line segments
A designer draws cross sections of an instrument panel in automobile interior design. Such drawings
often need to be segmented for further processing.
(1) Download the base code from the Canvas
(2) Fill MeasureCornerAngle function so that it can measure an angle at a corner of line segments.
Line segments is represented as an array of double in this program. X and Y coordinates of ith
point (zero based) is coord[i*2] and coord[i*2+1] This function must return 0.0 if the given
corner index is smaller than 1 or greater than the number of points-2. If you successfully fill this
function, you will see the following output on the console window.
Corner 1 Angle 5.625001
Corner 2 Angle 11.249998
Corner 3 Angle 11.250001
Corner 4 Angle 11.250000
Corner 5 Angle 5.931727
Corner 6 Angle 100.943270
Corner 7 Angle 78.749999
Corner 8 Angle 78.750001
Corner 9 Angle 78.947684
Corner 10 Angle 5.822681
Corner 11 Angle 11.250004
Corner 12 Angle 11.249996
Corner 13 Angle 11.250004
Corner 14 Angle 5.624998
(3) Fill DrawLineSegments function. This function must change the color of lines at every corner
where the corner angle is greater than 60 deg. The color sequence must be black, red, green,
blue, and repeat this sequence after the fourth color. If you implement this function
successfully, your line segments appear to be grouped into sub-groups. Your graphics window
will look like as follows.
7 Extra points: When the user clicks within 5 pixels of a line in the same-color group, draw the clicked
one in thick line. Use glLineWidth(5); When the user clicks on the corner shared by two same-color
groups, highlight either one of them (your program can pick one.)
(Base code available from the blackboard)
#include <stdio.h>
#include <math.h>
#include “fssimplewindow.h”
const double YsPi=3.1415927;
double MeasureCornerAngle(int nCoord,const double coord[],int index)
{
return 0.0;
}
void DrawLineSegments(int nCoord,const double coord[])
{
}
int main(void)
{
const int nCoord=16;
const double coord[nCoord*2]=
{
747.000000, 171.000000,
297.000000, 171.000000,
279.441871, 172.729325,
262.558491, 177.850842,
246.998679, 186.167735,
233.360390, 197.360390,
6.167735, 426.998679,
24.875801, 439.499009,
69.875801, 394.499009,
88.583867, 406.999340,
265.180195, 229.180195,
271.999340, 223.583867,
279.779246, 219.425421,
288.220936, 216.864662,
297.000000, 216.000000,
747.000000, 216.000000
};
for(int i=1; i<nCoord-1; i++)
{
printf(“Corner %d Angle %lf\n”,i,MeasureCornerAngle(nCoord,coord,i)*180.0/YsPi);
}
FsOpenWindow(16,16,800,600,1);
int key=FSKEY_NULL;
while(FSKEY_ESC!=key)
{
FsPollDevice();
key=FsInkey();
glClear(GL_DEPTH_BUFFER_BIT|GL_COLOR_BUFFER_BIT);
DrawLineSegments(nCoord,coord);
FsSwapBuffers();
FsSleep(20);
}
return 0;
}