Light Mapping

Ok, so I'm putting CLOD on hold for a bit, I'm not looking forward to be honest given I've pretty much forgotten everything to do with geometry. So instead I implemented light mapping. Light mapping is just darkening pixels on the terrain so it looks like a light is casting shadows. The simplest and most visually attractive technique in my opinion is slope lighting. Following a line of pixels in a direction from where the light source should be (in this case I chose south (which is x = 0, z = -1)), make the current pixel darker than the previous by a factor of how much higher the previous height is. If the previous pixel is lower than the current pixel, don't darken it.

shade = 1.0f - ((heightMap[x - xLightDir, z - zLightDir] - heightMap[x, z]) / softness);

As always you can play about with parameters to make the light come from a different direction, or to create a more severe (darker) shadow. Here's how the effect looks in practice on my engine (before and after):

It's not proper shadowing but I like the effect. I think it could be extended to stretch the shadows - for example a low sun would create long shadows, so you probably could choose a direction as above with a shadow range of 10 (something like x = 0, z = -10). However sections of the edges would look a bit out of place because they don't have 10 pixels before them.

For a realistic Irish effect you don't need shadows at all because there's no direct light source, just make sure to turn the colour of your ambient light to dark grey.