Normal map blending bug

[o.chabrand89]

When using the projection brush, and applying a material to it (SBS), the blending on my normal map is all messed up.

I want the normal map projection to replace the normal map underneath. If my layer blending is set to "normal combine" things look fine, however changing it to anything else, in particular to "normal" since thats the behaviour I want,  the edges of the projection (the "fading off" bits of my soft brush)  look all wrong!
Instead of blending softly into the background layer, they seem to blend into "flat" normal map color (the blueish neutral color)  and then suddenly (and jarringly) jump to the background normal map layer (leaving a messy looking seam)

incorrect blending in normal map



correct blending in base color



using substance painter 2019.2.0

system specs
Processor   Intel(R) Core(TM) i7-6700K CPU @ 4.00GHz, 4001 Mhz, 4 Core(s), 8 Logical Processor(s)

Installed Physical Memory (RAM)   32.0 GB

Name   NVIDIA GeForce GTX 960
Driver Version   25.21.14.1881

[Froyok]

This is expected : in order to blend properly our brush stroke done in the normal channel we flatten them with a default normal map color. It's fine with the default blending mode but won't work with other like normal or replace. This is a technical limitation at the moment. The best would be to add a mask to blend the borders of your painting manually.

[o.chabrand89]

Hmm that's too bad. I can see why it would be a complex color blending issue. I hope this gets some attention sometime as it makes material seam fixing rather difficult!
I suppose I can make a white mask and fade off the edges.

Thanks for the quick response!