Just a little bit of Gimp magic applied to the grass: Hue: -12, Brightness: +10 Saturation: +15
Plus a grayscale high-pass copy of the grass with some added contrast.
Nice... I think that should go into the base texture (unfortunately I'm not certain the one I've been grabbing for experiments is GPL compatible, so we still need a good grass texture - also somewhat less tiling of the texture would be good - anyone?).
The next question is of course - do we want the grass to be that dry? Or do we want to code HSV transformations in the shader, so we can change runtime from dry grass to fresh grass?
Maybe the darker patches could be a bit lighter and with a bit more variation in size. There also appears to be some periodicity.
Size variation is still the most expensive beast in the code. I'm trying to use as little noise scales as possible to keep framerates up. If framerate would not be an issue, I would get way better results, it's just a question of throwing enough variation at the problem.
I was wondering if you use colored bitmaps for the high-res overlays.
This is not a hires overlay - the base texture actually is hires, and the variation you see from higher altitude is just the dynamically generated color and shade variation and the heightmap shadows.
For the terrain, I'm using colored detail overlay textures. Pro - it gives you three different texture channels mixed from large distance, which helps getting rid of landclass boundaries and tiling. Con - it means the terrain doesn't ever become hires everywhere.
Again, if I had the performance, I'd simply use all 8 texture units available to use three different LOD ranges. But at my best estimate, that would get me to ~4 fps....
For everyone interested into making quality textures, I recommend the book "3d Game Textures" by Luke Ahearn. It's brilliant.
For anyone interested in making quality textures, I could do with some help in this area. I know how they have to look like, but I have neither time nor skill to get good GPL compatible textures on short notice.