stone displacement working but....

[kevin miller]

This is my first try at messing around with displacement. I am not finding alot of help on this as most displacement seems to be focused on landscapes and other organic forms. I want to texture a stone base on a house and I am having difficulty at making the corner look realistic with the variated edge you would see with stone. I tried to add a subdivide mod thinking more faces would make a better displacement. That seems to work but the edge (corner) seems to pull apart. This happens with/ without the subdivide mod. Is there a good way to have the stone continue around the corner with displacement looking good?

[kevin miller]

I did some more searching on this forum and found a post that was kind of helpful but not perfect. I tried to use the displacement mod in lieu of the displacement function in the material itself. The corner works much better but I can't seem to get a good displacement of the stone that matches the actual stone coursework. I am missing something somewhere. I took the two planes, added a UVw Map with box setting, added a subdivide mod, then added the displacement mod using my stone texture bump map. The problem is if I create more faces by using sub-divide or tessellate, the displacement occurs per those faces. That is okay except the actual coursework of cmu or ashlar type of stone should remain straight and not displace with it. By the way, I am using mental ray and not vray in case that matters for setting.

[jinsley]

before you do the sub divide mod, try chamfering the edges... I usually use 5 - 10 segments depending on how close to the camera... you might not even need the sub divide since it is mostly the edges you are worried about...

[Tommy L]

Invert the map and use a negative displacement value. This will pull the coursing inwards instead of pushing the stone outwards and should probably solve your corner gap problem.

[sandulea]

I had the same problem, and unfortunately it isn't covered much on the web. The most helpful resource I came across (the one that actually pointed me towards the root of the problem, the global displacement settings) was a blog on mrmaterials. I can't post the link because of the anti spam rule, search for "displacement and broken edges" or something.

 

Here's what I did: first of all, turn off the Smoothing in the Shadows and Displacement rollout under Renderer. Usually this one eliminates the effect almost completely, depending on the other settings.

 

Next, for a uniform displacement across the object, untick View. When on, it uses an on screen pixel as the unit of subdivision, and this creates the wavy, ripply artifact I experienced and showed in another thread, because of the dependence to the view instead of the object. Then set the Edge Length to whatever you feel is necessary. This controls the minimum length beyond which Max no longer subdivides the surface. Now that you unticked the View option, you will set the length in project units. This one works together with Max Subdivisions to determine the level of detail in your displacement, and it really affects render time. If there are too few subdivisions or the edge length is too small, it will again produce that kind of artifacts around the edges because it can't close the mesh properly in that area (or so I presume).

 

Finally you have the Max displace, which determines the maximum amplitude for your displacement. I don't know what it's supposed to do, if it's supposed to compress the peaks if they exceed this threshold, but mine seems to clip them when they do.

 

Finally, I use the Height Map Displacement shader from Mental Ray connection/displacement because it works almost always, and it works on objects imported from revit in FBX format.

 

Ultimately it's a balancing act between displacement height (both positive and negative), edge length and maximum subdivisions to achieve the optimal, problem-free, suitably detailed and sized displacement. Just turn off the View and Smoothing options and juggle with the other options I mentioned. I can't give you any numbers, I don't know what units you're using (I'm using milimeters) but I will if you're interested.