用DrawPrimitives::drawSolidPoly绘制一个实心多边形，代码如下：
local glNode = gl.glNodeCreate()
glNode:setContentSize(cc.size(size.width, size.height))
glNode:setAnchorPoint(cc.p(0.5, 0.5))
local function primitivesDraw(transform, transformUpdated)
gl.lineWidth(1)
local filledVertices = { cc.p(0,120), cc.p(50,120), cc.p(50,170), cc.p(25,200), cc.p(0,170) }
local fillColor = cc.c4f(0, 0, 1, 1)
cc.DrawPrimitives.drawSolidPoly(filledVertices, 5, fillColor)
end
glNode:registerScriptDrawHandler(primitivesDraw)
layer:addChild(glNode,-10)
glNode:setPosition( size.width / 2, size.height / 2)
问题描述：
fillColor更改r,g,b都有用，但是a不对，请问，这个a不是代表透明度吗？如果要设置实心区域的透明度怎么办呢？