Directed Erosion works in its own "Sculpt mode". In this example, we have a simple setup at 512 x 512 preview resolution. When you add the Directed Erosion node, you will notice it has its own independent resolution. In most cases, this should be the final output resolution.
Directed Erosion is intended for fine detailing, and works at an independent resolution from the preview and final build resolutions. This Sculpt Resolution can be upscaled or downscaled as needed.
In an effort to prevent memory excesses, the Sculpt mode will only show a 2048 x 2048 area. While the mini map in the sidebar let's you navigate the entire terrain, you can only see a 2K area at a time in the viewport.
Regardless of your target size, Directed Erosion's strokes are always processed at the same speed, whether at 2K or 32K.
The Erosion Tools become available when you enter the Sculpt mode. This floating window lets you select an erosion tool, modify its setting, and choose an erosion mode.
Each erosion tool creates a different effect. Some have secondary variations.
While properties differ between some tools, there is a general pattern:
The Erosion Tool panel provides a local "in-session" Undo function accessible next to the tools. You can undo up to 20 tool impacts.
When the Sculpt mode is active, your cursor in the viewport shows the impact area. The cursor flows over the terrain to show you the flow conditions and impact extents - very useful with large brush sizes.
Click anywhere on the terrain to create a "stroke" using the selected tool. In this case, we use the Landbreaker tool to create a few random strokes.
// TODO: Image
You will notice that, while the base terrain uses the preview resolution (512 x 512), the strokes and their effects on the terrain are at your sculpt's target resolution (2048 x 2048). This lets you preview the effect your final build will have regardless of your preview quality.
Once you are satisfied with your sculpt, turn the Sculpt mode off. You will notice that your high resolution sculpt is downscaled to the preview resolution, and may lose a lot of the detail.
If we switch the preview resolution to 2048 x 2048, the Directed Erosion node will reprocess the strokes and show them with higher fidelity.
Directed Erosion becomes moot if you process your terrain greatly. We recommend using it late in your graph after all the major shape changes are complete. This will save you hassles in the long run.
Here's a great way to separate the impact of Directed Erosion from the rest of your graph: save the output from your Graph, load that output in a new file using the File node, and then apply Directed Erosion to it.