We'll use the Extract tool to generate a displacement map from the shading information in a photo, or from normals in a normal map.

If a previous Displacement map is open, it will close so that we can start.

Open the Extract tool in the Map Tools area at the right, if it is not not already opened.

Start by selecting the Method which can be one of:

From Shading information in a photo.
From Normals in a normal map file.

Depending on which map you plan to use as source, select one of these two options.

Now select the actual source image by clicking in the Source drop menu.

You can choose to:

Use a currently open {PBR?Base Color|Diffuse} or Normal map.
Open from a file in your computer.
Paste an image from the Clipboard.
Drag'n'drop a file into the tool area (not into the Editor).

After selecting the source image, extraction will automatically start.

The extracted image will be of the same Width and Height as the source image. If by chance a Displacement map is currently open and is of different size, a window will appear asking which size to keep.

After extraction starts, new settings will appear allowing you to tune the extracted Displacement surface.

Use the Surface slider to control the surface relief. Lower values extract smoother maps with larger features but little fine detail, while higher values will extract crisper displacement. Try moving this slider to tune the extracted surface. (This setting is not available when extracting from Normals)

The Detail slider adds fine detail to the extracted surface. The leftmost position adds nothing, with higher values progressively adding fine and even medium-level detail.

And the Range slider allows you to control how far from each other are the topmost and bottommost points in the surface.

The extracted displacement can further refined or retouched with the other tools available, like the Keying or Paint tools.

To better grasp the extracted Displacement map, you can switch the Editor between the 2D or 3D views by clicking the button in the top-left corner of the Editor.

Zoom the displacement map in and out by rotating the mouse wheel. Or try dragging while pressing the right mouse button to rotate. And with the middle mouse button down, you can pan the displacement map.

The following video tutorials are related to map extraction:

Please watch in full screen by clicking the button at the bottom-right corner of the viewer.