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In GameGuru a _detail texture is simply a seamless tiled noise texture that overlays the model, it's for adding things like dirt.
All you need to do is put it in with your other textures and name it : nameoftexture_detail.format so for example if you had textures called BricksBanter_color.dds your detail texture would be BricksBanter_detail.dds
This is a guide i made when PBR was first added to gameguru:
https://forum.game-guru.com/thread/219411Primary Desktop:
i7 7700,k NV1070 8GB, 16GB 3200mhz memory, 1x 2TB Hybrid, Win10.
Secondary Desktop:
i5 4760k, NV960 2GB, 16GB 2333mhz memory, 1x 2TB Hybrid, Win10.
Primary Laptop:
i5, NV1050 4GB, 8GB memory, 1x 1TB HDD, Win10.
Secondary Laptop:
i3, Intel 4000 series graphics, 6GB memory, 1x 500gb HDD, Win8.1.
