cocos2d-x 类大全及其概要，难点

CCAffineTransform CCNode::nodeToParentTransform(void)
{
    if (m_bIsTransformDirty)
    {

        // Translate values
        float x = m_tPosition.x;
        float y = m_tPosition.y;

        if (m_bIgnoreAnchorPointForPosition)
        {
            x += m_tAnchorPointInPoints.x;
            y += m_tAnchorPointInPoints.y;
        }

        // Rotation values
        float c = 1, s = 0;
        if (m_fRotation)
        {
            float radians = -CC_DEGREES_TO_RADIANS(m_fRotation);
            c = cosf(radians);
            s = sinf(radians);
        }

        bool needsSkewMatrix = ( m_fSkewX || m_fSkewY );

        // optimization:
        // inline anchor point calculation if skew is not needed
        if (! needsSkewMatrix && !m_tAnchorPointInPoints.equals(CCPointZero))
        {
            x += c * -m_tAnchorPointInPoints.x * m_fScaleX + -s * -m_tAnchorPointInPoints.y * m_fScaleY;
            y += s * -m_tAnchorPointInPoints.x * m_fScaleX +  c * -m_tAnchorPointInPoints.y * m_fScaleY;
        }

        // Build Transform Matrix
        m_tTransform = CCAffineTransformMake( c * m_fScaleX,  s * m_fScaleX,
            -s * m_fScaleY, c * m_fScaleY,
            x, y );

        // XXX: Try to inline skew
        // If skew is needed, apply skew and then anchor point
        if (needsSkewMatrix)
        {
            CCAffineTransform skewMatrix = CCAffineTransformMake(1.0f, tanf(CC_DEGREES_TO_RADIANS(m_fSkewY)),
                tanf(CC_DEGREES_TO_RADIANS(m_fSkewX)), 1.0f,
                0.0f, 0.0f );
            m_tTransform = CCAffineTransformConcat(skewMatrix, m_tTransform);

            // adjust anchor point
            if (!m_tAnchorPointInPoints.equals(CCPointZero))
            {
                m_tTransform = CCAffineTransformTranslate(m_tTransform, -m_tAnchorPointInPoints.x, -m_tAnchorPointInPoints.y);
            }
        }

        m_bIsTransformDirty = false;
    }

    return m_tTransform;
}

上述代码中我一直不明白为什么m_bIgnoreAnchorPoint是true的时候，将m_tAnchorPointInPoints的坐标加入了原坐标。

if (m_bIgnoreAnchorPointForPosition)
{
    x += m_tAnchorPointInPoints.x;
    y += m_tAnchorPointInPoints.y;
}

后来才明白，这是为了补偿后面旋转带来的偏差的。

// optimization:
// inline anchor point calculation if skew is not needed
if (! needsSkewMatrix && !m_tAnchorPointInPoints.equals(CCPointZero))
{
    x += c * -m_tAnchorPointInPoints.x * m_fScaleX + -s * -m_tAnchorPointInPoints.y * m_fScaleY;
    y += s * -m_tAnchorPointInPoints.x * m_fScaleX +  c * -m_tAnchorPointInPoints.y * m_fScaleY;
}

static CCMotionStreak* create(float fade, float minSeg, float stroke, ccColor3B color, const char* path);
fade：残影残存时间。
misSeg：测试了一会发现没太多感觉。一般设置为3就可以了。
stroke：残影的宽度。
color：将会添加再残影纹理上的颜色。
stroke：是其中的path是纹理路径，

这个纹理将成为残影，color将会和纹理叠加。值得注意的是，这个类重载了setPosition并使用另外一个坐标变量，所以执行一些位置类运动会诡异的现象，如CCMoveBy，因为这些运动会通过原来的坐标变量来获取目标对象的起始坐标，但原来坐标已经被废弃。