Is it possible to add a "lightwarptexture" to a model through lua?

I am trying to make stuff in my gamemode look more cartoonish and make the shadows appear more sharp, but I do not know if that is possible.

I am trying to make the shadows more sharp also because gmods shadows are waaaaaayyyy to soft.

Textures are more easily controlled though VMT’s, which are the files that actually contain the texture parameters. In your case, you would have to edit the VMT’s of the models that you want to change with lightwarp commands.

Yes, it is possible. Check out the set functions here, You’ll need some basic understanding of VMTs but its fairly simple:
http://wiki.garrysmod.com/page/Category:IMaterial
Looking at this function in CapsAdmins’ TOD script may be helpful to you too:
https://github.com/CapsAdmin/tod/blob/master/lua/autorun/tod.lua#L168