// #include loads up library files, the order can matter
// generally load glut.h last
#include <stdio.h> // this library is for standard input and output
#include "glut.h"// this library is for glut the OpenGL Utility Toolkit
#include <math.h>
// this is the initialisation function, called once only
void init() {
glClearColor(0.0, 0.0, 1.0, 0.0); // set what colour you want the background to be
glMatrixMode(GL_PROJECTION); // set the matrix mode, we will look at this later
// set the projection window size in x an y.
gluOrtho2D(0.0, 500, 0.0, 500.0);
}
// this is the display function it is called when ever you want to draw something
// all drawing should be called form here
void circle() {
// draw circle
float theta;
glClear(GL_COLOR_BUFFER_BIT); // clear the screen using the background colour
glBegin(GL_POLYGON);
glColor3f(1.0, 0.0, 0.0); // set colour to red
for (int i = 0; i < 320; i++) {
theta = i * 3.142 / 180;
glVertex2f(190 + 50 * cos(theta), 250 + 70 * sin(theta));
}
glEnd();
glFlush(); // force all drawing to finish
}
// this has the effect of repeatedly calling the display function
void display() {
circle();
}
// as with many programming languages the main() function is the entry point for execution of the program
int main(int argc, char** argv) {
glutInit(&argc, argv); //perform the GLUT initialization
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); // more initialisation
glutInitWindowSize(800, 600); // set window position
glutInitWindowPosition(0, 0); // set window size
glutCreateWindow("Circle"); // create a display with a given caption for the title bar
init(); // call init function defined above
glutDisplayFunc(display); // define what function to call to draw
// the last function in the program puts the program into infinite loop
glutMainLoop();
// this line exits the program
return 0;
}
我添加了注释,以便您可以理解我的代码。该代码创建了一个大的红色圆圈,并切下了该圆圈的右下角,但我只想切下该底侧。我该如何实现?我非常感谢您的帮助。
像这样:
最佳答案
如果要用Secant line切圆,则必须定义起始角和终止角,并指定从起始点到终止角的圆点上的顶点坐标。
Full angle具有360度(2 * PI弧度)。底部(南)的 Angular 为-90度。
如果要在圆的底部切割零件,则可以这样计算起点和终点 Angular :
int cutsegment = 45;
int start = -90 + cutsegment / 2;
int end = 270 - cutsegment / 2;
for (int i = start; i <= end; i++) {
theta = i * 3.142 / 180;
glVertex2f(190 + 50 * cos(theta), 250 + 70 * sin(theta));
}