opengl style sprite shader in vex

[skydave]

Hi,

in opengl there are different blending modes for combining shaded fragments with the current color of the framebuffer. Different ways of blending functions are supported one of them being

source_color*source_alpha + destination_color*(1.0-source_alpha)

source_color and source_alpha is the color and alpha value of the fragment which is about to be written to the framebuffer. Think of it as the rgba value of a texture on some rendered geometry. destination_color is the current color in the framebuffer.

My question is: is it possible to model this behaviour in vex somehow? Want I want to achieve is to scatter some grids and apply some texture with an alpha channel to them without any lighting etc. pretty basic stuff. I dont want to use sprites. I have been trying hard to get this stuff working with decal material but if I have more grids the blended result becomes brighter (http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=2402). I have been looking at this thread http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=10406 but they use sprites and a layered surface shader which for some reason I can not create in houdini11(apprentice). I found another thread where the topic creator wants to do exactly the same as I want: http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=13342. There people suggest to use the glass shader. I tried to play with it but I couldn't get it to do what I want (actually I couldn't get it do do anything). Also I think it is a bit overkill for the simple thing I am trying to do.

Thanks for any feedback in advance,

Dave

P.S.: in case its not obvious from my question: I'm a noob