cocos2d-x版本为2.0.4
此画图调用的是opengl es 2.0版本，支持三角形画图。故必须有一个顶点数组。此定义定义在CCSprite.h中
ccV3F_C4B_T2F_Quad m_sQuad;
而这个顶点数组的定义为
//! 4 ccVertex3FTex2FColor4B typedef struct _ccV3F_C4B_T2F_Quad { //! top left ccV3F_C4B_T2F tl; //! bottom left ccV3F_C4B_T2F bl; //! top right ccV3F_C4B_T2F tr; //! bottom right ccV3F_C4B_T2F br; } ccV3F_C4B_T2F_Quad;
顶点分布如图所示
Cocos2d-x的画图均在自身节点的draw(void)下面。
1 // m_pobTexture 为当前CCSprite绑定的纹理图 2 if (m_pobTexture != NULL) 3 { 4 ccGLBindTexture2D( m_pobTexture->getName() ); 5 } 6 else 7 { 8 ccGLBindTexture2D(0); 9 } 10 11 //启用顶点数组画图模式 12 ccGLEnableVertexAttribs( kCCVertexAttribFlag_PosColorTex ); 13 //设置每个顶点数的大小 14 #define kQuadSize sizeof(m_sQuad.bl) 15 long offset = (long)&m_sQuad; 16 17 // vertex 18 int diff = offsetof( ccV3F_C4B_T2F, vertices); 19 glVertexAttribPointer(kCCVertexAttrib_Position, 3, GL_FLOAT, GL_FALSE, kQuadSize, (void*) (offset + diff)); 20 21 // texCoods 22 diff = offsetof( ccV3F_C4B_T2F, texCoords); 23 glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, kQuadSize, (void*)(offset + diff)); 24 25 // color 26 diff = offsetof( ccV3F_C4B_T2F, colors); 27 glVertexAttribPointer(kCCVertexAttrib_Color, 4, GL_UNSIGNED_BYTE, GL_TRUE, kQuadSize, (void*)(offset + diff)); 28 29 //这一步为确认画图，根据当前绑定的纹理图，然后根据当前的顶点数组进行画图 30 glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
GL_TRIANGLE_STRIP
- OpenGL 的使用将最开始的两个顶点出发，然后遍历每个顶点，这些顶点将使用前2个顶点一起组成一个三角形。
所以画图的顺序为 V0-V1-V2 及 V1-V2-V3两个三角形，这样就画出我们想展示的图形
