1. Making a Simple Displacement Surface
2. Alpha Masking

Blending Two Textures

To make our terrain look even more realistic, we can transition gradually from one texture to another using the "Paint Alpha" tool. The textures that support this feature have the prefix "blend" in their names.

Instead of "Paint Geometry", we'll click on the "Paint Alpha" button to change the displacement tool to this mode. You need to pick a texture that supports alpha mask blending in the original displacement, and drag your mouse over the displacement surface to apply the secondary texture effect. The transition between the primary and the secondary textures should appear gradual.

Alpha masking

Visibility and Leaks

One very important thing to keep in mind while working with displacement surfaces is that they do not block VIS. If you are unfamiliar with the concept of VIS blocking, read this tutorial first.

Consequently, if you're making a large cliff or hill, you might want to create a solid brush with the "tools/toolsnodraw" texture inside the displacement surface to enhance performance. Otherwise, the engine will render whatever is on the other side of the cliff or hill all the time, even though the player cannot see those things.

Using nodraw textured solid brush to block VIS

That's the basics of displacement surface. I'll discuss more advanced uses of displacement surface in another tutorial. Here is the in-game shot:

Displacement surface in-game