Is there a way to smoothly blend the edges of different materials on one mesh into each other?
For example, one face is glossy while the one next to it is matt - can I make it so they smoothly transition into each other rather than having a hard, visible edge where the faces meet?
Blender render, yes. Cycles, no.
As described where the two faces are “assigned” different materials, not that I am aware of.
However if they are assigned the same material, you can fake it. So long as the geometry is simple enough.
One simple way is to use a gradient texture with a color ramp to adjust the falloff. Then plug that in to a mix shader as the factor between two shaders. One matte, the other glossy.
Is this helpful for you?