CRYENGINE uses a special approach with Detail maps, often referred to as "Unified" or "Merged" detail maps.
The reason for this is Detail maps in CRYENGINE include not only Normals information, but also Diffuse and Gloss information.
Channels are organized as follows:
- Red: Diffuse
- Green: Normal Red
- Blue: Gloss
- Alpha: Normal Green
If you're converting an existing Normal map into a Detail map, you can take the existing Red/Green channels and place them in the Green/Alpha channels respectively.
To showcase how to create a Merged Detail Map, we're going to take an existing RGB Normal map:
From Left to Right: RGB Channels, Red Channel, Green Channel, Blue Channel.
Create an Alpha channel and place the Green Channel into it.
Select the Red channel and paste that into the Green channel.
The texture should now look something like this:
Now, for the Red and Blue channels we're going to add a Diffuse and a Gloss map.
Pick a suitable Diffuse texture and place it in the Red channel then pick a suitable Gloss texture and place it in the Blue channel.
Left: Greyscale Diffuse, Right: Greyscale Glossmap
The texture should now look something like this (depending on the luminosity of the R/B channels, color may vary):
From Left to Right: RGB Channels, Red Channel, Green Channel, Blue Channel, Alpha Channel.
Two options are available for Merged Detail Maps: Detail_MergedAlbedoNormalsSmoothness (Using BC7 compression) or an additional _Lossless format.
Note that the Lossless format should be used with care as file size will be 4x larger.
Detail Maps are most often tiled fairly heavily, this means you can use smaller resolutions without noticeable a loss in quality as texel density will be high due to the tiling.