Dark edges using disp material

[John Ferris]

Any way to get rid of the odd dark edges? It's a stone displacement material applied to a solid. I tried radiusing and chamfering the edges - still didn't look right. ACAD file, material and image attached (hope they're not too big for posting...). Thanks - John

[Roy Hirshkowitz]

It's a pretty tough application for displacement mapping. Displacements alter the geometry based on the map value-- both the geometry and the texture map have to be continuous at the corner for things to match up exactly.

For the geometry piece of the equation, filleting will likely help-- chamfering probably won't.

For the map piece-- you need to find some sort of mapping that's continuous. In the case of a column like this, a cylindrical map may work.

Also make sure you haven't changed the default Z Offset setting (or whatever I call it) for the map-- that can make things worse at corners.

[Jan Verzelen]

I always tought that changing the z offset affected the edges. I changed the value from -0.5 to -1 and the dark edges dissapear. On the other hand, there's not much elevation left on the edges, so changing to -0.9 brings on a little bit of structure on the edges but the dark edge becomes a little visible also.(see image attached) Am i right in my conclusion or am i just messing around?

[John Ferris]

Thanks Jan...I think that will work. I can fine tune a happy medium between the black line and seeing some edge structure. Good to know. I appreciate your help and time - John

[Jan Verzelen]

you're welcome.

[Roy Hirshkowitz]

You're sort of correct-- it affects where the midpoint of the displacement occurs vertically. Usually the default is the best setting for corners-- but not always.

Z offset doesn't affect the total amount of displacement-- that's another setting.

[Jan Verzelen]

I know that z offset doesn't affect displacement, height does. But the effect becomes less visible at corners when the z-offset changes, see attachement.

[Ros. Riha]

z offset -1 makes edges straight and sharp.....and displacement is used to make them look more natural, so by increasing z offset you are losing one of effects why you used displacement in the first place...

[John Ferris]

Thanks Roy. Good info. Appreciate your time and efforts - John