每天一个OpenGL程序 第六篇 图形的组合绘制

#include <windows.h>

#include <gl/gl.h>

#include <gl/glut.h>

#include <math.h>

// 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;

}