Looking really good. Can you share more about this ^ ?
Yeah sure!
I tested many approach to make the ground, which is not nicely trimmed grass, so not easy. It's wild mix of sand, grass gaining back some ground and reworked areas leaving bare soil exposed, not to mention rock on the hills.
A track that has a similar effect is Lilski's Bridghampton. Still one of the top mod track out there, even after a few years, IMO. So I basically took a page from Lilski's playbook for the ground shaders (all credit go to him for figuring out this stuff long ago!).
The short story is that I used ksMultilayer_fresnel_nm. But instead of using the txDiffuse to assign color (such as I did for asphalt) it's just a neutral texture (see image below). So you get the true color of RGB channel texture assigned according to txMask that show. I used 4K texture for each Mask. There's 8 of them to cover the entire track, to get fine details such as small grass patch.
The long story:
First (in Blender) I merged all my ground terrain up to the track edge in one object. I then assigned different areas with its own "RGB_LAND_XX" material. Then for each section I had a pure green 4K image to assign.
Then unwrapped each section(smart UV unwrap).
At that point you can export and test with a basic grass texture on the G channel to get things going. You do need the grass texture in DXT5 dds with alpha channel almost pitch black everywhere to get correct results.
The magic happens when you get into texture painting in Blender. You do need to install some brush. I had to make my own based on black and white images found on the web.
Once you have that setup properly you can start painting with red and blue depending on which material you want. I simply followed the aerial photo for the roads with a round brush, but used splatter brushes for the details near the edges of the track.
*** big reminder *** do not forget to save the image (Blender doesn't save it automatically...at least in 2.79).
The big illumination for me came when I realized that ksEditor seamlessly mapped the same texture accross different sections (that have different material - if you have fresnel shader for all section), this is so powerful!
Another thing is that with darker blue or red mask you can almost have another material (say very dark sand looks like soil, just by going darker on the blue channel). This can free a slot for another texture to add in the mix.
Note that in-between color (RGB mixing of textures) generaly don't look great, most pixels on the RGB Mask should be mostly saturated with one color (R, G or B), meaning relatively sharp brushes should be used.
Note: When you combine that with the CSP Grass FX, it's a huge time saver because you'll have fancy grass closly following where the ground is green (not bothering with classic 3D grass after that). Tweaking config file is recommended to get best results.
For the final touch, I post-process the Mask image made in Blender into my image editor to add an extra layer of variation with a black & white variation texture (set to multiply) to create darker and lighter spots (has to be done on all RGB mask textures to get exposure consitent across all the track.
TxDiffuse (64x64 pixels)
A post-processed 4K mask texture
