TUTORIAL - Mixing normalmaps (Patreon)

UPDATE:
Made a Photoshop Action that does what is explained in this tutorial, simply run it over the normalmap you want to add in your existing normalmap, and it'll do all the steps. For 2k Textures, otherwise a little tweak tot he action is needed.

If you have a normalmap and a detailmap (pattern) like witcher 3 armors have, you'll want to combine them.

How to do this without losing any detail? 

 Overlaying one normalmap to the other is not enough, the blue channell will lose a great deal of information, resulting in loss of depth in your normalmap.  

So we need to do a few edits to our PATTERN layer.
Start by duplicating it, We'll call it ADD and SUB.  

In the ADD layer:
Image> Adjustments> Levels

Image > Adjustments> Channel Mixer

In the SUB layer: Image> Adjustments> Levels

Image > Adjustments> Channel Mixer

Now You'll have to go to the ADD layer and set its mode to linear dodge (add). I have renamed the ADD layer to linear dodge (add).

While the SUB layer, will still need more tweaks. Duplicate it and NAME one layer RG - Difference (red and green channel) and B- Exclusion (blue channel). Set the layer mode to DIFFERENCE for the RG -  difference layer and to EXCLUTION to the B - Exclusion layer.

Now you'll have to REMOVE the unwanted channel information in those layers. You'll have to select the BLACK color in your paintbrush and paint the BLUE channel black for the RG - Diff layer, and he RED and GREEN channels for the B - exclusion layer.

And your mixed nomalmap is finished.  

You can download Witcher 3 tileable patterns below.

All rights belong to CDPR, and thus their distribution permission apply here.
(no paywall, no claiming of partnership\affiliation,credit).
I am simply uploading the files.