(Draft)
Vegetation LODs are stored in R:\graphics\stuff\jungle\decors_textures\vegetations
Open 3dsmax file
Remove everything except the billboard and the object
Disable any VertexTreePaint modifiers on the object
Select the LOD and split it in a front and side view, using Detach
On the front LOD add a Projection modifier
Pick the object
Reset the automatic projection, and move the projection cage forward, so it's in front of the tree
Do the same on the side LOD
Edit the material of the object so that any transparent materials are using a Standard material, with the texture Mono output set to the Alpha channel
Set the Environment ambient color to white, and tint to black
Select the front LOD
Render To Texture, enable Projection(, Pick the object)
Do the same for the side LOD
Select both
Add Diffuse map output
Use existing unwrap channel
(Make sure the projection is still OK, repeat reset & move if necessary)
Set the map size as needed, 4 times larger, rescale afterwards
Set padding to 0 when rendering alpha, set to 8 when rendering color
Select both and render
Disable the opacity on the material for rendering the colors, just render alpha once