Using Blend node with flahs renderer

I found below sentences about flash transparent.

“Is there a possibility to set the background of the flash transparent?
This seems to be a limitation of the Flash ActiveX. There is no way to use a flash movie with alpha in vvvv.
We once worked around this with two flash movies, one for the alpha and one for the content which were combined in a shader. If you can spare some colors, you could also use a chromakeying shader. Easiest way would be simply using the Add mode of the Blend node for that - but it will sure look different.”

How can i connect blend node with flash renderer??

Would somebody explain more detail about that.

If you make a Blend (EX9.renderstate) node, and you connect it to a quad, it would look to all pixels BELOW the layer (pixels from other quads in the group) and it will calculate what to do with the according to the blend mode.

This will only work proper if you have 2 or more quads on a group (EX9) node, otherwise there is not that much to calculate.

The Blend (EX9.renderstate) set to Multiple will make all the colours below 50% grey ‘transparent’ (at least, in photoshop), so it makes all the white transparent. (Blend mode set to ADD does the opposite, making white show).

I attached a 10 second hack from the flash renderer helpfile, hope you get the picture. Though this all works, it is not the best solution (because you can’t use the colour white on your top layer), but when in need. (7.3 kB)