ah cool thanks, found it. this one helped in particular. Now I can feed velocity into shader forge… just have to find out what zw|x means… zw stands for x and z velocity, no idea how to get the y velocity though 
edit: I guess the y velocity is somehow incorporated into the x and z direction, that might be what that zw |x is hinting at. because in shaderforge I only get to access uvzw when using velocity in the stream. U and V behave static as they always do and are just plain UVs, zw are modulated by velocity and hopefully somehow incorporate the y direction…
edit2: a kk, zw seem to describe two angles, that could be why a third component is missing. I don’t get it 
aaaahhh, it seems they are kind of physical velocity vectors, again only two of them… but cool.