OpenGL入门笔记(四)

本文介绍如何使用OpenGL绘制三维图形,并通过实例演示了绘制一个旋转的三角形和四边形的过程。文章详细解释了如何设置顶点位置、颜色及旋转角度等参数。

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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( 
0.0f1.0f0.0f);                    
        glColor3f(
0.0f,1.0f,0.0f);                        
        glVertex3f(
-1.0f,-1.0f1.0f);                    
        glColor3f(
0.0f,0.0f,1.0f);                        
        glVertex3f( 
1.0f,-1.0f1.0f);                

        glColor3f(
1.0f,0.0f,0.0f);                        
        glVertex3f( 
0.0f1.0f0.0f);                
        glColor3f(
0.0f,0.0f,1.0f);                        
        glVertex3f( 
1.0f,-1.0f1.0f);                
        glColor3f(
0.0f,1.0f,0.0f);                    
        glVertex3f( 
1.0f,-1.0f-1.0f);                

        glColor3f(
1.0f,0.0f,0.0f);                        
        glVertex3f( 
0.0f1.0f0.0f);                    
        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( 
0.0f1.0f0.0f);                
        glColor3f(
0.0f,0.0f,1.0f);                        
        glVertex3f(
-1.0f,-1.0f,-1.0f);                
        glColor3f(
0.0f,1.0f,0.0f);                        
        glVertex3f(
-1.0f,-1.0f1.0f);                
        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( 
1.0f1.0f,-1.0f);                
        glVertex3f(
-1.0f1.0f,-1.0f);                
        glVertex3f(
-1.0f1.0f1.0f);                    
        glVertex3f( 
1.0f1.0f1.0f);                    

        glColor3f(
1.0f,0.5f,0.0f);                    
        glVertex3f( 
1.0f,-1.0f1.0f);                
        glVertex3f(
-1.0f,-1.0f1.0f);                
        glVertex3f(
-1.0f,-1.0f,-1.0f);                    
        glVertex3f( 
1.0f,-1.0f,-1.0f);                

        glColor3f(
1.0f,0.0f,0.0f);                    
        glVertex3f( 
1.0f1.0f1.0f);                
        glVertex3f(
-1.0f1.0f1.0f);                
        glVertex3f(
-1.0f,-1.0f1.0f);                
        glVertex3f( 
1.0f,-1.0f1.0f);            
        glColor3f(
1.0f,1.0f,0.0f);                    
        glVertex3f( 
1.0f,-1.0f,-1.0f);                
        glVertex3f(
-1.0f,-1.0f,-1.0f);                
        glVertex3f(
-1.0f1.0f,-1.0f);                
        glVertex3f( 
1.0f1.0f,-1.0f);                    

        glColor3f(
0.0f,0.0f,1.0f);                    
        glVertex3f(
-1.0f1.0f1.0f);                
        glVertex3f(
-1.0f1.0f,-1.0f);                
        glVertex3f(
-1.0f,-1.0f,-1.0f);                
        glVertex3f(
-1.0f,-1.0f1.0f);                

        glColor3f(
1.0f,0.0f,1.0f);                    
        glVertex3f( 
1.0f1.0f,-1.0f);                
        glVertex3f( 
1.0f1.0f1.0f);                
        glVertex3f( 
1.0f,-1.0f1.0f);                    
        glVertex3f( 
1.0f,-1.0f,-1.0f);                
    glEnd();                                        

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


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