cocos2d-x学习笔记03:绘制基本图元

第一部分:基本图形绘制

cocos2dx封装了大量opengl函数,用于快速绘制基本图形,这些代码的例子在,tests\DrawPrimitivesTest目录下

注意,该方法是重载node的draw方法实现的,在智能机上,并不推荐直接绘制几何图形,因为大量的坐标编码会极大降低工作效率,应尽量使用Image。而且cocos2dx的渲染机制会造成前后遮挡问题,尤其是几何图形与图片等其他node混合绘制时。

void HelloWorld::draw() {    

        CCLayer::draw(); 

        CCSize s = CCDirector::sharedDirector()->getWinSize(); 

        // 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); 

        ccDrawLine( CCPointMake(0, 0), CCPointMake(s.width, s.height) ); 



        // line: color, width, aliased 

        // glLineWidth > 1 and GL_LINE_SMOOTH are not compatible 

        //注意:线宽>1 则不支持GL_LINE_SMOOTH 

        // GL_SMOOTH_LINE_WIDTH_RANGE = (1,1) on iPhone 

        glDisable(GL_LINE_SMOOTH); 

        glLineWidth( 5.0f ); 

        /*glColor4ub(255,0,0,255);*/ 

        glColor4f(1.0, 0.0, 0.0, 1.0); 

        ccDrawLine( CCPointMake(0, s.height), CCPointMake(s.width, 0) ); 



        // TIP: 

        // If you are going to use always the 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 

        // 注意:cocos2dx绘制的是方块点 

        glPointSize(64); 

        /*glColor4ub(0,0,255,128);*/ 

        glColor4f(0.0, 0.0, 1.0, 0.5); 

        ccDrawPoint( CCPointMake(s.width / 2, s.height / 2) ); 



        // draw 4 small points 

        // 注意:cocos2dx绘制的是方块点 

        CCPoint points[] = { CCPointMake(60,60), CCPointMake(70,70), CCPointMake(60,70), CCPointMake(70,60) }; 

        glPointSize(4); 

        /*glColor4ub(0,255,255,255);*/ 

        glColor4f(0.0, 1.0, 1.0, 1.0); 

        ccDrawPoints( points, 4); 



        // draw a green circle with 10 segments 

        glLineWidth(16); 

        /*glColor4ub(0, 255, 0, 255);*/ 

        glColor4f(0.0, 1.0, 0.0, 1.0); 

        //参数依次是:中心点,半径,角度,分段数,是否连接中心点 

        ccDrawCircle( CCPointMake(s.width/2,  s.height/2), 100, 0, 10, false); 



        // draw a green circle with 50 segments with line to center 

        glLineWidth(2); 

        /*glColor4ub(0, 255, 255, 255);*/ 

        glColor4f(0.0, 1.0, 1.0, 1.0); 

        ccDrawCircle( CCPointMake(s.width/2, s.height/2), 50, CC_DEGREES_TO_RADIANS(90), 50, true);   



        // open yellow poly 

        /*glColor4ub(255, 255, 0, 255);*/ 

        glColor4f(1.0, 1.0, 0.0, 1.0); 

        glLineWidth(10); 

        CCPoint vertices[] = { CCPointMake(0,0), CCPointMake(50,50), CCPointMake(100,50), CCPointMake(100,100), CCPointMake(50,100) }; 

        //参数依次是:点数组,点数量,是否封闭 

        ccDrawPoly( vertices, 5, false); 



        // closed purple poly 

        /*glColor4ub(255, 0, 255, 255);*/ 

        glColor4f(1.0, 0.0, 1.0, 1.0); 

        glLineWidth(2); 

        CCPoint vertices2[] = { CCPointMake(30,130), CCPointMake(30,230), CCPointMake(50,200) }; 

        ccDrawPoly( vertices2, 3, true); 



        // draw quad bezier path,绘制有一个控制点的贝塞尔曲线 

        ccDrawQuadBezier(CCPointMake(0,s.height), CCPointMake(s.width/2,s.height/2), CCPointMake(s.width,s.height), 50); 



        // draw cubic bezier path,绘制有两个控制点的贝塞尔曲线 

        ccDrawCubicBezier(CCPointMake(s.width/2, s.height/2), CCPointMake(s.width/2+30,s.height/2+50), CCPointMake(s.width/2+60,s.height/2-50),CCPointMake(s.width, s.height/2),100); 



        

        // restore original values,恢复opengl的正常参数 

        glLineWidth(1); 

        /*glColor4ub(255,255,255,255);*/ 

        glColor4f(1.0, 1.0, 1.0, 1.0); 

        glPointSize(1);     

}

第二部分:字符串绘制

1. 锚点

cocos2dx的字符串绘制使用的是Label,cocos2dx并不直接支持在屏幕中绘制字符串(这是有道理的,因为我们不能直接把一个string做成一个节点,那样很难理解),如果要直接绘制的话,可以自己封装opengl函数(网上有很多例子,一般是用texture做)。为了便于字体对齐,我们在很多游戏引擎中,都使用对齐锚点的功能,如j2me的anchor参数接口。默认情况下,锚点在(0,0)处。为了说明锚点的设置对字体对齐的影响,我们使用如下代码:

bool HelloWorld::init() {

    if ( !CCLayer::init() ) {

        return false;

    }

    CCSize size = CCDirector::sharedDirector()->getWinSize();

    CCLabelTTF* pLabel = CCLabelTTF::create("Hello World", "Thonburi", 64);

    pLabel->setAnchorPoint(ccp(0,0.5));//设置锚点,默认是在node的中心,即锚点为(0.5,0.5),显示为居中对齐

    pLabel->setPosition(ccp(size.width / 2, size.height/2));

    this->addChild(pLabel, 1);



    draw();

    return true;

}

//重载CCLayer的draw函数,然后绘制十字线;

void HelloWorld::draw() {

    CCLayer::draw();

    CCSize s = CCDirector::sharedDirector()->getWinSize();

    glEnable(GL_LINE_SMOOTH);

    ccDrawLine( CCPointMake(0, s.height/2), CCPointMake(s.width, s.height/2) );

    ccDrawLine( CCPointMake(s.width/2, 0), CCPointMake(s.width/2, s.height) );

}
 

可以看到,cocos2dx默认锚点是node的中心。你自己可以设置不同的锚点,使文本具有不同的对齐方式。

2.显示中文字体

第三部分:绘制图片

cocos2dx中并没有直接绘制图片的概念,我们一般是使用CCSprite。核心代码如下:

CCSize size=CCDirector::sharedDirector()->getWinSize();

    CCSprite* pSprite = CCSprite::create("HelloWorld.png"); 

    //pSprite->setFlipX(true); //可以手动设置图形旋转和镜像,而不是使用Action,因为有许多Action是个过程,而不是直接显示结果;

    pSprite->setFlipY(true);

    //pSprite->setRotation(90); 

    pSprite->setPosition(ccp(size.width/2, size.height/2)); 

    this->addChild(pSprite, 0);

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