displacement

[Andrew West]

 I have been stumped for months now on how to get  displacement maps to work within my material editor.   Essentially I am looking to create a stone wall that is displaced and wraps around a corner.  Anyone out there who has figured it out?  I have a material that I have created for masonry.  In the editor I have given it a bump map (dirt) and a displacement map (my stone wall) and turned them on.  The preview in the editor looks pretty good.  I have displacement turned on in my render options.  The render output shows the bumps in my reflection channel only but no matter what I do I can never get the displacement to show.  The object is even meshed to see if that would help. 

FYI I have used the displacement tool in the V-ray tools palette with limited success.  That tool is seems to allow for displacement of meshed objects but it does not allow for proper placement or even scaling of the texture .  Using it on anything other than a surface object gives horrible results at the edges.  As the stone turns the corner I get a thick black squiggly line.  see attachment

 

[Tech]

Andrew,

While displacement creates a nice rendering effect, it's weakness is edge conditions. The object's normals affect the displacement. To create the hard edge of a cube, form•Z will split the normals along the edge (ie one pointing in each direction of the adjacent faces). This will also be reflected in the displacement as you have observed.

 

The workaround is to make the entire object render as smooth (Attributes->Smooth Shading->Facetted Objects->All Faces). See attached UI and resulting rendering. Note that there still can be slightly “roughness” where the patterns align unless you have a pattern that is designed for alignment (like the second example).

 

The displacement uses the object's texture controls. A technique for setting up the mapping is to make a material with the diffuse texture that uses the desired displacement map. Use the texture tools to set the mapping type and parameters. If you do not want to use this material for the result, then assign a different material to the object once the desired mapping is established.

 

We are consulting with Chaos Group if there is a way for us to have separate normal channels (and UV texture channels) for shading and displacement which would allow us to automate this behind the scene and give the desired shading across the faces. We will also be adjusting the UI to allow for a negative displacement amount. This might create better results in these cases.

 

We hope this helps!

BWB.bmp