OpenGL入门笔记（四）

前面一直在画二维图形，其实三维图形的绘制就是以其为基础，可以说二维不过是三维的一种特例（相当与Z=0）。比如说要画一个正方体，它有上下左右前后共六个面组成，也就是要画出六个正方形就可以了，只是要注意绘制时应该按逆时针绘制（好像是进行纹理映射时需要的。。。）

     

      我们必须将OpenGL屏幕想象成一张很大的画纸，后面还带着许多透明的层。差不多就是个由大量的点组成的立方体。这些点从左至右、从上至下、从前到后的布满了这个立方体。如果能想象的出在屏幕的深度方向，就应该在设计新3D对象时没有任何问题。

int DrawGLScene(GLvoid)                                
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);    
    glLoadIdentity();                                
    glTranslatef(-1.5f,0.0f,-6.0f);                        
    glRotatef(rtri,0.0f,1.0f,0.0f);                    
    glBegin(GL_TRIANGLES);                                
        glColor3f(1.0f,0.0f,0.0f);                        
        glVertex3f( 0.0f, 1.0f, 0.0f);                    
        glColor3f(0.0f,1.0f,0.0f);                        
        glVertex3f(-1.0f,-1.0f, 1.0f);                    
        glColor3f(0.0f,0.0f,1.0f);                        
        glVertex3f( 1.0f,-1.0f, 1.0f);                

        glColor3f(1.0f,0.0f,0.0f);                        
        glVertex3f( 0.0f, 1.0f, 0.0f);                
        glColor3f(0.0f,0.0f,1.0f);                        
        glVertex3f( 1.0f,-1.0f, 1.0f);                
        glColor3f(0.0f,1.0f,0.0f);                    
        glVertex3f( 1.0f,-1.0f, -1.0f);                

        glColor3f(1.0f,0.0f,0.0f);                        
        glVertex3f( 0.0f, 1.0f, 0.0f);                    
        glColor3f(0.0f,1.0f,0.0f);                    
        glVertex3f( 1.0f,-1.0f, -1.0f);                    
        glColor3f(0.0f,0.0f,1.0f);                    
        glVertex3f(-1.0f,-1.0f, -1.0f);                

        glColor3f(1.0f,0.0f,0.0f);                    
        glVertex3f( 0.0f, 1.0f, 0.0f);                
        glColor3f(0.0f,0.0f,1.0f);                        
        glVertex3f(-1.0f,-1.0f,-1.0f);                
        glColor3f(0.0f,1.0f,0.0f);                        
        glVertex3f(-1.0f,-1.0f, 1.0f);                
        glColor3f(0.0f,1.0f,0.0f);
        glVertex3f(-1.0f,-1.0f,1.0f);
        glColor3f(0.0f,0.0f,1.0f);
        glVertex3f(1.0f,-1.0f,1.0f);
        glColor3f(0.0,1.0f,0.0f);
        glVertex3f(1.0f,-1.0f,-1.0f);
        glColor3f(0.0f,0.0f,1.0f);
        glVertex3f(-1.0f,-1.0f,-1.0f);
    glEnd();                                        

    glLoadIdentity();                                
    glTranslatef(1.5f,0.0f,-7.0f);                        
    glRotatef(rquad,1.0f,1.0f,1.0f);                
    glBegin(GL_QUADS);                                
        glColor3f(0.0f,1.0f,0.0f);                        
        glVertex3f( 1.0f, 1.0f,-1.0f);                
        glVertex3f(-1.0f, 1.0f,-1.0f);                
        glVertex3f(-1.0f, 1.0f, 1.0f);                    
        glVertex3f( 1.0f, 1.0f, 1.0f);                    

        glColor3f(1.0f,0.5f,0.0f);                    
        glVertex3f( 1.0f,-1.0f, 1.0f);                
        glVertex3f(-1.0f,-1.0f, 1.0f);                
        glVertex3f(-1.0f,-1.0f,-1.0f);                    
        glVertex3f( 1.0f,-1.0f,-1.0f);                

        glColor3f(1.0f,0.0f,0.0f);                    
        glVertex3f( 1.0f, 1.0f, 1.0f);                
        glVertex3f(-1.0f, 1.0f, 1.0f);                
        glVertex3f(-1.0f,-1.0f, 1.0f);                
        glVertex3f( 1.0f,-1.0f, 1.0f);            
        glColor3f(1.0f,1.0f,0.0f);                    
        glVertex3f( 1.0f,-1.0f,-1.0f);                
        glVertex3f(-1.0f,-1.0f,-1.0f);                
        glVertex3f(-1.0f, 1.0f,-1.0f);                
        glVertex3f( 1.0f, 1.0f,-1.0f);                    

        glColor3f(0.0f,0.0f,1.0f);                    
        glVertex3f(-1.0f, 1.0f, 1.0f);                
        glVertex3f(-1.0f, 1.0f,-1.0f);                
        glVertex3f(-1.0f,-1.0f,-1.0f);                
        glVertex3f(-1.0f,-1.0f, 1.0f);                

        glColor3f(1.0f,0.0f,1.0f);                    
        glVertex3f( 1.0f, 1.0f,-1.0f);                
        glVertex3f( 1.0f, 1.0f, 1.0f);                
        glVertex3f( 1.0f,-1.0f, 1.0f);                    
        glVertex3f( 1.0f,-1.0f,-1.0f);                
    glEnd();                                        

    rtri+=0.2f;                                            
    rquad-=0.15f;                                        
    return TRUE;                                        
}