OpenGL学习笔记（二） 绘制图形

#include <GL/glut.h>

#include <math.h>
const GLfloat Pi = 3.1415926536f;
void myDisplay(void)
{
    GLfloat a = 1 / (2 - 2 * cos(72 * Pi / 180));
    GLfloat bx = a * cos(18 * Pi / 180);
    GLfloat by = a * sin(18 * Pi / 180);
    GLfloat cy = -a * cos(18 * Pi / 180);
    GLfloat
        PointA[2] = { 0, a },
        PointB[2] = { bx, by },
        PointC[2] = { 0.5, cy },
        PointD[2] = { -0.5, cy },
        PointE[2] = { -bx, by };

    glClear(GL_COLOR_BUFFER_BIT);
    // 按照A->C->E->B->D->A的顺序，可以一笔将五角星画出
    glBegin(GL_LINE_LOOP);
    glVertex2fv(PointA);
    glVertex2fv(PointC);
    glVertex2fv(PointE);
    glVertex2fv(PointB);
    glVertex2fv(PointD);
    glEnd();
    glFlush();
}

int main(int argc, char* argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(400, 400);
    glutCreateWindow("第一个OpenGL程序");
    glutDisplayFunc(&myDisplay);
    glutMainLoop();

    return 0;
}

（一）glVertex2i(1, 3);
（二）glVertex2f(1.0f, 3.0f);
（三）glVertex3f(1.0f, 3.0f, 0.0f);
（四）glVertex4f(1.0f, 3.0f, 0.0f, 1.0f);
（五）GLfloat VertexArr3[] = {1.0f, 3.0f, 0.0f};
glVertex3fv(VertexArr3);