每天一个OpenGL程序 第六篇 图形的组合绘制

#include
#include
#include
#include

// 练习6.1 基本图形的组合绘制

void render();
void initGL();

void main(int argc,char** argv)
{
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);
glutInitWindowPosition(100,150);
glutInitWindowSize(320,320);
glutCreateWindow("模拟时钟");
glutDisplayFunc(render);
glutIdleFunc(render);
initGL();
glutMainLoop();
}

void initGL()
{
glViewport(0,0,320,320);
glOrtho(-100,100,-100,100,-100,100);
glClearColor(0,0,0,1);
}

//根据长度创建表针
void createClockPointer(float size)
{
glBegin(GL_LINES);
glVertex2f(0,0);
glVertex2f(size,0);
glEnd();
}

GLfloat hR = 20; //时针长度
GLfloat mR = 30; //分针长度
GLfloat sR = 45; //秒针长度
GLfloat cR = 57; //表盘半径

GLfloat doublePI =  2 * 3.1415936; //2π
GLfloat step = doublePI/24; //绘制圆形的角度切分

GLfloat Hstep = doublePI/12; //小时刻度的角度切分
GLfloat Sstep = doublePI/60; //分秒刻度的角度切分

GLfloat Sangle; //秒针旋转的角度
GLfloat Mangle; //分针旋转的角度
GLfloat Hangle; //时针旋转的角度

void render()
{
glClear(GL_COLOR_BUFFER_BIT);
//绘制外盘
glBegin(GL_POLYGON);
for (GLfloat angle = 0.0; angle < doublePI + step; angle += step)
{
glColor3f(0.6f,0.4f,0.12f);
GLfloat y = cR * sin(angle);
GLfloat x = cR * cos(angle);
glVertex2f(x,y);
}
glEnd();

//绘制内盘
glBegin(GL_POLYGON);
for (angle = 0.0; angle < doublePI + step; angle += step)
{
glColor3f(0,0,0);
GLfloat y = (cR-2) * sin(angle);
GLfloat x = (cR-2) * cos(angle);
glVertex2f(x,y);
}
glEnd();

//绘制秒针刻度
glBegin(GL_LINES);
for (angle = 0.0; angle < doublePI + Sstep; angle += Sstep)
{
glColor3f(0.6f,0.4f,0.12f);
GLfloat y = (cR-2) * sin(angle);
GLfloat x = (cR-2) * cos(angle);

GLfloat y2 = (cR-4) * sin(angle);
GLfloat x2 = (cR-4) * cos(angle);

glVertex2f(x2,y2);
glVertex2f(x,y);
}
glEnd();

//绘制刻度
glBegin(GL_LINES);
for (angle = 0.0; angle < doublePI + Hstep; angle += Hstep)
{
glColor3f(0.6f,0.4f,0.12f);
GLfloat y = (cR-4) * sin(angle);
GLfloat x = (cR-4) * cos(angle);

GLfloat y2 = (cR-7) * sin(angle);
GLfloat x2 = (cR-7) * cos(angle);

glVertex2f(x2,y2);
glVertex2f(x,y);
}
glEnd();

//绘制秒针
glPushMatrix();
glRotatef(Sangle,0,0,1);
glColor3f(1.0f,0.0f,0.0f);
createClockPointer(sR);
glPopMatrix();

//绘制分针
glPushMatrix();
glRotatef(Mangle,0,0,1);
glColor3f(0.0f,1.0f,0.0f);
createClockPointer(mR);
glPopMatrix();

//绘制时针
glPushMatrix();
glRotatef(Hangle,0,0,1);
glColor3f(0.0f,0.0f,1.0f);
createClockPointer(hR);
glPopMatrix();

glutSwapBuffers();
glFlush();

Sangle -= 1.8;
Mangle -= 0.3;
Hangle -= 0.05;
}