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December 17, 2020 08:24
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//LIANG BARKSY ALGORITHM | |
#include <GL/glut.h> | |
#include <stdio.h> | |
double xmin = 50, xmax = 100, ymin = 50, ymax = 100; | |
double r[4], p[4], q[4]; | |
void init() { | |
glClearColor(0, 0, 0, 1); | |
glClear(GL_COLOR_BUFFER_BIT); | |
gluOrtho2D(0, 500, 0, 500); | |
} | |
void drawRectangle(float x0, float y0, float x1, float y1) { | |
glColor3f(1.0, 0.0, 0.0); | |
glBegin(GL_LINE_LOOP); | |
glVertex2f(x0, y0); | |
glVertex2f(x1, y0); | |
glVertex2f(x1, y1); | |
glVertex2f(x0, y1); | |
glEnd(); | |
} | |
void drawLine(float x0, float y0, float x1, float y1) { | |
glColor3f(0.0, 1.0, 0.0); | |
glBegin(GL_LINES); | |
glVertex2f(x0, y0); | |
glVertex2f(x1, y1); | |
glEnd(); | |
} | |
double maximum() { | |
int i; | |
double max = 0; | |
for (i = 0; i < 4; i++) { | |
if (p[i] < 0) { | |
if (max < r[i]) { | |
max = r[i]; | |
} | |
} | |
} | |
return max; | |
} | |
double minimum() { | |
int i; | |
double min = 1; | |
for (i = 0; i < 4; i++) { | |
if (p[i] > 0) { | |
if (min > r[i]) { | |
min = r[i]; | |
} | |
} | |
} | |
return min; | |
} | |
void liang_barsky(double x0, double y00, double x1, double y11) { | |
double x = x0, y = y00; | |
double t1 = 0, t2 = 1; | |
double dx = x1 - x0; | |
double dy = y11 - y00; | |
int i; | |
int reject = 0; | |
p[0] = -dx; | |
q[0] = x0 - xmin; | |
p[1] = dx; | |
q[1] = xmax - x0; | |
p[2] = -dy; | |
q[2] = y00 - ymin; | |
p[3] = dy; | |
q[3] = ymax - y00; | |
for (i = 0; i < 4; i++) { | |
if (p[i] == 0 && q[i] < 0) { | |
reject = 1; | |
break; | |
} else { | |
r[i] = q[i] / p[i]; | |
} | |
} | |
t1 = maximum(); | |
t2 = minimum(); | |
drawRectangle(200 + xmin, 200 + ymin, 200 + xmax, 200 + ymax); | |
if (t1 > t2) { | |
} else { | |
if (reject == 1) { | |
} else { | |
x1 = x + (dx * t2); | |
y11 = y + (dy * t2); | |
x0 = x + (dx * t1); | |
y00 = y + (dy * t1); | |
drawLine(x0 + 200, y00 + 200, x1 + 200, y11 + 200); | |
glFlush(); | |
} | |
} | |
} | |
void display() { | |
double x0 = 50, y00 = 110, x1 = 100, y11 = 110; | |
drawRectangle( xmin, ymin, xmax, ymax); | |
drawLine(x0, y00, x1, y11); | |
liang_barsky(x0, y00, x1, y11); | |
glFlush(); | |
} | |
int main(int argc, char * argv[]) { | |
glutInit( & argc, argv); | |
glutInitWindowSize(750, 750); | |
glutCreateWindow("liang barsky algorithm"); | |
init(); | |
glutDisplayFunc(display); | |
glutMainLoop(); | |
return 0; | |
} |
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