I'm looking for info on directly editing height and splat map data. My initial thought was that GDI with it's premade brushes would be an asset. So I set about learning what i needed from GDI to get the DXTexture into an HDC for use in a window.I've used BltBit which copies the entire Pixels RGB data from the dx surface into the HDC of my window.
I would prefer to copy a single SRC channel ( R,G,B,or A for the splat layers(1-4)), leaving the rest of the DST bitmap black. After a brush has affected the bitmap, I intend to copy the single channel back to the initial DXTexture, which is used as a splat map in my terrain viewer(hopefully editor)
Another thought was skipping GDI directly, and and implementing brushes in DX(unless they exist in an area i'm not familiar with) using pixel shaders, and modifying textures directly that way.
I'd appreciate a nudge in the right direction, if anyone has a spare moment.