首先参考这篇文章绘制一个球体:

我们知道球体的参数方程是这样的：

x=r·sin(α)·cos(β)

椭圆的参数方程是：

x=rx·sin(α)·cos(β)

在这个基础上进行一些修改就可以实现椭圆的绘制了！

代码实现如下：

/***************************************************************************** Copyright: 2012, ustc All rights reserved. contact:k283228391@126.com File name: main.c Description:using opengl in SDL. Author:Silang Quan Version: 1.0 Date: 2012.12.01 *****************************************************************************/ #include 
     
       #include 
      
        #include 
       
         #include 
        
          #include 
         
           #include 
          
            #define pi 3.1415926 SDL_Surface *screen; typedef struct Point3f { GLfloat x; GLfloat y; GLfloat z; }point; int getPoint2(GLfloat rx,GLfloat ry,GLfloat rz,GLfloat a,GLfloat b,point &p) { p.x=rx*sin(a*pi/180.0)*cos(b*pi/180.0); p.y=ry*sin(a*pi/180.0)*sin(b*pi/180.0); p.z=rz*cos(a*pi/180.0); return 1; } point* getPointMatrix2(GLfloat rx,GLfloat ry,GLfloat rz,GLint slices) { int i,j,w=2*slices,h=slices; float a=0.0,b=0.0; float hStep=180.0/(h-1); float wStep=360.0/w; int length=w*h; point *matrix; matrix=(point *)malloc(length*sizeof(point)); if(!matrix)return NULL; for(a=0.0,i=0;i
           
            sym ) { case SDLK_ESCAPE: quit( 0 ); break; case SDLK_SPACE: break; default: break; } } void resizeGL(int width,int height) { if ( height == 0 ) { height = 1; } //Reset View glViewport( 0, 0, (GLint)width, (GLint)height ); //Choose the Matrix mode glMatrixMode( GL_PROJECTION ); //reset projection glLoadIdentity(); //set perspection gluPerspective( 45.0, (GLfloat)width/(GLfloat)height, 0.1, 100.0 ); //choose Matrix mode glMatrixMode( GL_MODELVIEW ); glLoadIdentity(); } void handleEvents() { // Our SDL event placeholder. SDL_Event event; //Grab all the events off the queue. while( SDL_PollEvent( &event ) ) { switch( event.type ) { case SDL_KEYDOWN: // Handle key Event handleKeyEvent( &event.key.keysym ); break; case SDL_QUIT: // Handle quit requests (like Ctrl-c). quit( 0 ); break; case SDL_VIDEORESIZE: //Handle resize event screen = SDL_SetVideoMode(event.resize.w, event.resize.h, 16, SDL_OPENGL|SDL_RESIZABLE); if ( screen ) { resizeGL(screen->w, screen->h); } break; } } } void initSDL(int width,int height,int bpp,int flags) { // First, initialize SDL's video subsystem. if( SDL_Init( SDL_INIT_VIDEO ) < 0 ) { fprintf( stderr, "Video initialization failed: %s\n", SDL_GetError( ) ); quit( 1 ); } atexit(SDL_Quit); //Set some Attribute of OpenGL in SDL SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 5 ); SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 5 ); SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 5 ); SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 ); SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); //Set the video mode screen= SDL_SetVideoMode( width, height, bpp,flags); if(!screen ) { fprintf( stderr, "Video mode set failed: %s\n",SDL_GetError( ) ); quit( 1 ); } resizeGL(screen->w, screen->h); //Set caption SDL_WM_SetCaption( "OpenGL Test", NULL ); } void renderGL() { // Clear the color and depth buffers. glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT ); // We don't want to modify the projection matrix. */ glMatrixMode( GL_MODELVIEW ); glLoadIdentity( ); // Move down the z-axis. glTranslatef( 0.0, 0.0, -25.0 ); glRotatef(50.0f,0,1,1); //Draw a square drawSphere(10,20); //drawOval(5,8,15,20); SDL_GL_SwapBuffers( ); } void initGL( int width, int height ) { float ratio = (float) width / (float) height; // Our shading model--Gouraud (smooth). glShadeModel( GL_SMOOTH ); // Set the clear color. glClearColor( 0, 0, 0, 0 ); // Setup our viewport. glViewport( 0, 0, width, height ); //Change to the projection matrix and set our viewing volume. glMatrixMode( GL_PROJECTION ); glLoadIdentity(); gluPerspective( 60.0, ratio, 1.0, 100.0 ); } int main( int argc, char* argv[] ) { // Dimensions of our window. int width = 640; int height = 480; // Color depth in bits of our window. int bpp = 32; int flags= SDL_OPENGL|SDL_RESIZABLE; //Set the SDL initSDL(width, height, bpp,flags); //Set the OpenGL initGL( width, height ); //main loop while(true) { /* Process incoming events. */ handleEvents( ); /* Draw the screen. */ renderGL( ); } return 0; }