Dirt from all edges?

[voon]

If I create a cube in blender, use a mixmaterial and control the emount of my by the dirt node, it will only come from below ... z axis on the surface. I watched other videos where people use something else than Blender, and the did the same ... basic cube, basic two mateirals, dirt node .... and it comes in from all sides, i.e. ever edge is nicely "dirted" ... not so in Blender.

How can this be done?

[kubicki3d]

Maybe "Invert Normal" is what you're looking for?

Cheers
Szymon