Hi Jeremie,
I thought that might be the case.
A curvature map shows white in the convex regions (i.e., edges), black in the concave regions and neutral gray in neutral regions. The convexity map only shows white in the convex regions and black everywhere else.
In Mari, blurring the curvature map does the same thing Painter does, namely shows the seams. However, blurring the convexity map does not show seams. I thought that using a convexity map in Painter, instead of a curvature map would resolve the seam issue.
I guess, I will just give it a try and see what happens. I imagine it may be problematic though, as materials/smart materials would expect a curvature map with black, white and gray.