Get Depth Value of Depth Buffer

In the material editor, when we use the node SceneTexture with texture id SceneDepth, we get the scene depth in clip space. However, we want to get the depth value(called DeviceZ in Common.ush) that is stored in the depth buffer. We can use the function float ConvertToDeviceZ(float SceneDepth) and float ConvertFromDeviceZ(float DeviceZ) to convert between each other.

Since there is no dedicated expression node for either of them, we have to create a custom material expression manually.

1. Create a custom material expression with an input node SceneDepth and an output type CMOT Float 1.
2. Add ConvertToDeviceZ(SceneDepth) to the Code field.
3. Pass the result of SceneTexture:SceneDepth to the custom expression node.