Normal map rendering blocky shading/ shadows

Question

I hope I don't seem like I'm spamming but I've looked around this site and google for advice and non of it is really helping.

My problem is that if I use the normal map I baked from my high-poly rock model (2nd one in the image) then the normals are completely fine. If I use the normal map I created from the diffuse using Bitmap2Material and specify that it's an OpenGL normal map I still get these blocky shadow areas on my normal map but the map itself is totally fine:

(I've intentionally used a jped in this example so I can upload, but the real file itself is a PNG, about 4.7mb)

Anyone know why this is happening and how I can fix it? The reason I want to use the normal map generated from the diffuse is that it contains more of a bumpy texture and it looks nicer than the baked normal in comparison.

Here's the normal map working totally fine in the texture program:

Solutions tried: smoothing edges, vertecies, faces in edit mode. Setting faces to smooth shaded. Opening my normal map in photoshop and re-saving it to see if it alters the data somehow. Changing from colour to non-colour data. Playing with normal intensity.

Answer 1

I couldn't figure out the solution as to why my normal map was giving me such harsh quad shading. I opened it in other programs and determined that the normal map generated from the baked diffuse I used on the rock always contained harsh edges even though the normal map itself doesn't show it.

Instead I found this incredible tool for combining normal maps and used my original baked normal map and combined it with another to give it more texture. The method I used was to open the broken normal map into gimp2, turn it back&white and then use the gimp2 normal map plugin to turn it back into a normal map.

https://www.blendswap.com/blends/view/76176 <<< This is the combine normal map tool I used. Huge thanks to RadCapricorn for uploading this.

Here's my result:

So agian in bullet points:

-Take broken N-map into Gimp2 -Turn it greyscale and edit contrast according to how much detail you prefer -Use Gimp2 normal map plugin found here: https://code.google.com/archive/p/gimp-normalmap/downloads and a cute tutorial on how to use it here: https://www.youtube.com/watch?v=8Jdo3ZmtPWk

Then if you want to combine the normal map with your original baked one then:

Use this blend file: https://www.blendswap.com/blends/view/76176

Follow the instructions contained within the blend file itself.

New blender 2.8 shortcut to save images: SHIFT+S (it's no longer F2)