DrawPrimitive真是一個好類！！cocos的開發組干了好事。

DrawPrimitive真是一個好類！！cocos的開發組干了好事。

如果每次在商業項目中使用opengl命令去繪制特效，工作效率真心低，所以官方包裝了這個接口，真實好東西。

draw函數的接口以及改了，新接口不允許重載原先的void draw(void)。

命令模式已是過去，顯示列表模式則是將命令放入緩沖池中，在opengl狀態機執行繪制命令時從中讀取才去繪制，不再是每次繪制就調用opengl狀態機立即繪制。

這就要求引擎全局組織繪制命令，即openglcocos2d::CustomCommand

class CustomCommand : public RenderCommand
{
public:
    CustomCommand();
    ~CustomCommand();
    
public:

    void init(float depth);

    void execute();

    inline bool isTranslucent() { return true; }
    std::function func;

protected:
};

render執行單個RenderCommand時就是調用execute函數，最後訪問額func成員，從而執行下面的onDraw。

最後產生一堆繪制命令。等待真正opengl去執行，實際上每條繪制函數的命令都會去flush一次。

代碼是演示效果：VisibleRect來自testCpp，或者說下面整段來自testCpp。

void HelloWorld::draw(Renderer *renderer, const Mat4 &transform, uint32_t flags)
{
    m_customCommand.init(_globalZOrder);
    m_customCommand.func = CC_CALLBACK_0(HelloWorld::onDraw, this, transform, flags);
    renderer->addCommand(&m_customCommand);
}


void HelloWorld::onDraw(const Mat4 &transform, uint32_t flags)
{
    Director* director = Director::getInstance();
    director->pushMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
    director->loadMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW, transform);
    
    //draw
    CHECK_GL_ERROR_DEBUG();
    
    // draw a simple line
    // The default state is:
    // Line Width: 1
    // color: 255,255,255,255 (white, non-transparent)
    // Anti-Aliased
    //  glEnable(GL_LINE_SMOOTH);
    DrawPrimitives::drawLine( VisibleRect::leftBottom(), VisibleRect::rightTop() );
    
    CHECK_GL_ERROR_DEBUG();
    
    // line: color, width, aliased
    // glLineWidth > 1 and GL_LINE_SMOOTH are not compatible
    // GL_SMOOTH_LINE_WIDTH_RANGE = (1,1) on iPhone
    //  glDisable(GL_LINE_SMOOTH);
    glLineWidth( 5.0f );
    DrawPrimitives::setDrawColor4B(255,0,0,255);
    DrawPrimitives::drawLine( VisibleRect::leftTop(), VisibleRect::rightBottom() );
    
    CHECK_GL_ERROR_DEBUG();
    
    // TIP:
    // If you are going to use always thde same color or width, you don't
    // need to call it before every draw
    //
    // Remember: OpenGL is a state-machine.
    
    // draw big point in the center
    DrawPrimitives::setPointSize(64);
    DrawPrimitives::setDrawColor4B(0,0,255,128);
    DrawPrimitives::drawPoint( VisibleRect::center() );//中心的圓點，藍色正方向
    
    CHECK_GL_ERROR_DEBUG();
    
    // draw 4 small points
    Vec2 points[] = { Vec2(60,60), Vec2(70,70), Vec2(60,70), Vec2(70,60) };
    DrawPrimitives::setPointSize(4);
    DrawPrimitives::setDrawColor4B(0,255,255,255);
    DrawPrimitives::drawPoints( points, 4);//四個青色點
    
    CHECK_GL_ERROR_DEBUG();
    
    // draw a green circle with 10 segments
    glLineWidth(16);
    DrawPrimitives::setDrawColor4B(0, 255, 0, 255);
	DrawPrimitives::drawCircle( VisibleRect::center(), 100, 2, 10, false);
    
    CHECK_GL_ERROR_DEBUG();
    
    // draw a green circle with 50 segments with line to center
    glLineWidth(2);
    DrawPrimitives::setDrawColor4B(0, 255, 255, 255);
    DrawPrimitives::drawCircle( VisibleRect::center(), 200, CC_DEGREES_TO_RADIANS(90), 50, true);
    
    CHECK_GL_ERROR_DEBUG();
    
    // draw a pink solid circle with 50 segments
    glLineWidth(2);
    DrawPrimitives::setDrawColor4B(255, 0, 255, 255);
    DrawPrimitives::drawSolidCircle( VisibleRect::center() + Vec2(140,0), 40, CC_DEGREES_TO_RADIANS(90), 50, 1.0f, 1.0f);
    
    CHECK_GL_ERROR_DEBUG();
    
    // open yellow poly
    DrawPrimitives::setDrawColor4B(255, 255, 0, 255);
    glLineWidth(10);
    Vec2 vertices[] = { Vec2(0,0), Vec2(50,50), Vec2(100,50), Vec2(100,100), Vec2(50,100) };
    DrawPrimitives::drawPoly( vertices, 5, false);//左下角的方形
    
    CHECK_GL_ERROR_DEBUG();
    
    // filled poly
    glLineWidth(1);//五角星
    Vec2 filledVertices[] = { Vec2(0,120), Vec2(50,120), Vec2(50,170), Vec2(25,200), Vec2(0,170) };
    DrawPrimitives::drawSolidPoly(filledVertices, 5, Color4F(0.5f, 0.5f, 1, 1 ) );
    
    
    // closed purble poly
    DrawPrimitives::setDrawColor4B(255, 0, 255, 255);
    glLineWidth(2);
    Vec2 vertices2[] = { Vec2(30,130), Vec2(30,230), Vec2(50,200) };
    DrawPrimitives::drawPoly( vertices2, 3, true);
    
    CHECK_GL_ERROR_DEBUG();
    
    // draw quad bezier path 中間這條線
    DrawPrimitives::drawQuadBezier(VisibleRect::leftTop(), VisibleRect::center(), VisibleRect::rightTop(), 50);
    
    CHECK_GL_ERROR_DEBUG();
    
    // draw cubic bezier path 上面的線
    DrawPrimitives::drawCubicBezier(VisibleRect::center(), Vec2(VisibleRect::center().x+30,VisibleRect::center().y+50), Vec2(VisibleRect::center().x+60,VisibleRect::center().y-50),VisibleRect::right(),100);
    
    CHECK_GL_ERROR_DEBUG();
    
    //draw a solid polygon
    Vec2 vertices3[] = {Vec2(60,160), Vec2(70,190), Vec2(100,190), Vec2(90,160)};
    DrawPrimitives::drawSolidPoly( vertices3, 4, Color4F(1,1,0,1) );
    
    // restore original values
    glLineWidth(1);
    DrawPrimitives::setDrawColor4B(255,255,255,255);
    DrawPrimitives::setPointSize(1);
    
    CHECK_GL_ERROR_DEBUG();
    
    //end draw
    director->popMatrix(MATRIX_STACK_TYPE::MATRIX_STACK_MODELVIEW);
}

西。

const Vec2& center,

float radius,

float angle,---------這個參數有什麼用？沒看懂，測試了也感覺不出區別。。終於找到了，相對於x軸正方向旋轉方向。比如：從90*pi/180度即y軸正方向與圓交點的位置

unsigned int segments,：圓邊被切成多少段線段

bool drawLineToCenter：圓心到起始繪制點是否繪制線段

void drawCircle( const Vec2& center, float radius, float angle, unsigned int segments, bool drawLineToCenter)
{
    drawCircle(center, radius, angle, segments, drawLineToCenter, 1.0f, 1.0f);
}