This is exactly the explanation I was looking for. I wasn't getting any hits for "ZBrush/Tangent Basis", and this is exactly the issue. I can't thank you enough, Cryrid. I suppose it was too convenient to be able to just hit "export all" and go make coffee. Now if anyone can solve "Issue B" I'll be sucking diesel.
Issue B, your green channel is -Y and being interpreted as +Y, solutions include Baking as +Y in Xnormal, inverting your green channel in Gimp/Photoshop or telling the program to interpret as -Y (that one isn't possible in max). Shortlist of programs and their (default) normal map swizzle 3dsMax +Y Blender -Y Maya -Y…
Thank You. After four full working days of hand-wringing and research I've finally caved: I cannot solve this problem on my own. Apologies if this has been covered, but I really cannot find a solution anywhere. I cannot figure out what's causing the artifacts in the 1st normal map above. Viewed in DirectX/Stingray 3DSMax…