cocos2d-x学习笔记03：绘制基本图元-阿里云开发者社区

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 DrawPrimitivesTest::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);
//恢复opengl的正常参数
// restore original values
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 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）。

其实最简单的绘制例子就是最开始的那个Helloworld。核心代码如下：

// Create a label and initialize with string "Hello World".
CCLabelTTF* pLabel = CCLabelTTF::labelWithString("Hello World", "Thonburi", 64);
CC_BREAK_IF(! pLabel);
// Get window size and place the label upper.
CCSize size = CCDirector::sharedDirector()->getWinSize();
pLabel->setPosition(ccp(size.width / 2, size.height - 20));
// Add the label to HelloWorld layer as a child layer.
this->addChild(pLabel, 1);