I want to create a procedural quilted pattern by using shader displacement.
I thought I had a good setup as seen on the left side in black and white. When looking at it in black and white it seems fine. But when displacing (especially with a color) you can see it seems pointy instead of a soft curve.
Could anybody maybe help me why the displacement looks sharp while the black and white texture seems smooth?
It's a combination of color management and perception. Textures that are not smooth numerically (i.e., that lead to non-smooth displacements) may appear quite smooth when viewed as colors.
In your case, the Voronoi texture with F1/Minkowski distance outputs a decidedly non-smooth texture, with diagonal seams and sharp points at the maximums. A quick fix is to switch from "F1" to "Smooth F1" which reduces these sharp edges. Then, instead of using "Power" and "Brightness/Contrast" nodes which are hard to control, try mapping the Voronoi Distance into a reasonable range with a Map Range node and fine tuning the result with the Float Curve. You'll probably need to adjust the Displacement Scale as well. With a little fiddling, I came up with this modification to your network:
which looks like it's in the ballpark:
Here's the modified Blend file.
