A few more things on Erosion

I mentioned in the last post that there are several improvements to Erosion coming, including a hardness input.

But that’s not the only improvement..

Better Masking

The mask input on Erosion previously did a simple alpha-blend between the results and the input. This is.. adequate. One consequence is that the mask is not actually used to guide the erosion itself, ie the masked area doesn’t “sit” well against the rest of the eroded terrain.

Under the next version, the Mask input is an “active” mask. That is, it actually participates in the erosion process:

• Fully masked areas will be completely unaffected, as with previous.
• Areas outside the mask will now be eroded accounting for the masked area. This is probably what you figured it should do in the first place 🙂 The difference is hard to describe, but profound; for example, a masked area in a low basin that would previously have been filled quickly with sediment will instead stay unfilled, acting as a “sediment sink” for surrounding areas.
• Areas that are completely masked will no longer generate any waterflow. This means that masked erosion will be much faster.  Fully masked-off areas take relatively negligible time to process.

The main thing that prompted this change was to make terrain with rivers work better with erosion. Now you can simply take the river channel mask, pipe it (inverted) into the erosion mask, and boom!

The river now “sits” much nicer into an eroded terrain. As a nice bonus, the hero-river systems will effectively transport away sediment for the hillslope erosion, just like in real life…

In the last picture above, you can see the effect of the river transporting sediment; the surrounding valley becomes steeply carved with gullies as the river effectively participates in the erosion process! Not bad for a simple mask input 😉