hello, I have this issue. In 3ds max is a modifier vertexpaint. This modifier allows me to pick an rgb color and paint verticies by that color. But I need to draw alpha value too. I can pick only RGB color even when I switch to alpha channel. How do I specify alpha value to paint with? When I switch to alpha cannel I see white color over my mesh, so I tried to draw with black color, but in export script , if I access alpha component of vertex colors I allways get 255. So how do I correctly alter alpha component of a vertex color by vertex paint tool?

Just add 2 vertex paint modifiers.. one for color one for alpha
Then just paint black to the alpha vp modifier

use 'getMapSupport' maxscript functions to check the data:
meshOp.getMapSupport <mesh> <channel>
color channel = 0
illum channel = -1
alpha channle = -2

Use the 'Layers' section in the vertex_paint floater

I first add alpha vp modifier and then color vp modifier to stack. But When I paint black to alpha one, alpha values of all verticies are still 255. What exactly should I do in other to have finally altered the alpha value? What layer mode should I use? Or where can I do a mistake?