opengl画椭圆

-(void)draw:(CGPoint) center rx:(float)rx ry:(float)ry a:(float)a segs:(int )segs drawLineToCenter:(BOOL)drawLineToCenter{
    
    int additionalSegment = 1;
    if (drawLineToCenter)
        additionalSegment++;
    
    const float coef = 2.0f * (float)M_PI / segs;
    
//       float* vertices =   2 * (segs + 2); 
    float  vertices[2*(segs+2)];
    if(!vertices)
    {
        return;
    }
    memset(vertices, 0, sizeof(float) * 2 * (segs + 2));
    
    float rads, distance, angle, j, k;
    for(int i = 0; i <= segs; ++i)
    {
        rads = i * coef;
        distance = sqrt(pow(sinf(rads) * rx, 2) + pow(cosf(rads) * ry, 2));
        angle = atan2(sinf(rads) * rx, cosf(rads) * ry);
        j = distance * cosf(angle + a) + center.x;
        k = distance * sinf(angle + a) + center.y;
        
        vertices[i*2] = j * CC_CONTENT_SCALE_FACTOR();
        vertices[i*2+1] = k * CC_CONTENT_SCALE_FACTOR();
    }
    vertices[(segs+1)*2] = center.x * CC_CONTENT_SCALE_FACTOR();
    vertices[(segs+1)*2+1] = center.y * CC_CONTENT_SCALE_FACTOR();
    
    // Default GL states: GL_TEXTURE_2D, GL_VERTEX_ARRAY, GL_COLOR_ARRAY, GL_TEXTURE_COORD_ARRAY
    // Needed states: GL_VERTEX_ARRAY, 
    // Unneeded states: GL_TEXTURE_2D, GL_TEXTURE_COORD_ARRAY, GL_COLOR_ARRAY    
    glDisable(GL_TEXTURE_2D);
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_COLOR_ARRAY);
    
    glVertexPointer(2, GL_FLOAT, 0, vertices);    
    glDrawArrays(GL_LINE_STRIP, 0, (GLsizei) segs+additionalSegment);
    
    // restore default state
    glEnableClientState(GL_COLOR_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glEnable(GL_TEXTURE_2D);    
    
//    delete[] vertices;
 

}

调用方法，放到for中可以是实心的

 for(int i = 0 ;i<100;i++){ 

        [self draw:ccp(1024/2,768/2) rx:10  ry:57-i a:M_PI segs:200 drawLineToCenter:NO];

 }