So I went with rivers. I took the simple way out for this and used the same noise functions I've been using for everything else. Eventually I settled on a stripped down version of the pattern used for the big mountains so that rivers naturally travel in the valleys and creases between them.
There is also a bit of erosion added, which is more visible in the flatter, lower areas. Noise values are converted to absolute values (all negatives become flipped) so areas near 0 are lowered in height and the closest to 0 areas are where the rivers are made.
(The more eagle-eyed lot might notice some faint grid lines running along the mountains- this is a visual bug related to raycasting unable to access voxel info from adjacent chunks. This would be fixed eventually.)
I want to fix this also for steeper areas because the water looks a bit odd taking on the shape of the mountains. But it's a good start. The rivers tend to travel more in the flatter areas, because I put a hard cap on height on where they begin.
And then come biomes. These depend on a set of variables also provided by, yep, noise functions. A set of Simplex noise patterns with very low frequencies have subtle changes on the local scale (from the player's point of view) but are very apparent across the entire world. They're essentially the same patterns that made the world maps in this previous post. And so they will affect other things such as humidity and temperature. Biomes affect the color of Surface blocks and eventually, vegetation, enemy types and materials scattered around.
My approach to biomes will not be to use different classes for different biomes, or even divide the world up into discrete regions. Instead the regions will be formed implicitly by the noise patterns. I will go in detail more as I flesh out the biome system later. Here is an example of a desert biome.
For now, I just hardcoded the terrain to show the desert biome using the desert surface colors. What I really wanted to show here is how rivers change the humidity on a very local level. If we look at the other side of the peak we can see some sort of an oasis.
Humidity in this case can also mean the moisture level in the ground. Areas are grassy around rivers, even in the desert. With smart object placement, there will also be shrubs and trees in these areas.
That's all for now. I want to get the biome rules more defined in order to make the biomes transition well over different parts of the world.