Hi Jamie - sorry maybe I wasn't clear with that cylinder test - the object in that previous cylinder test was not a "default cylinder" created by MoI, it was a test file set up similar to a model made up of multiple surfaces.

I made it by cutting a default cylinder into several different segments.

It's just an easy way to see what will happen on a more complex model made up of multiple surfaces that are joined together instead of just one big surface.


Probably your Blender one is just a default cylinder created in Blender? It most likely has not been cut up into different pieces, that's why there is a difference.


But there is also a pretty big difference between a polygon model that is created in a poly modeling program like Blender versus one that is generated from NURBS surfaces in a CAD program like MoI.


In a poly modeler you never actually have a "true" cylinder shape at all, it's all set up to work with polygons only and may use things like smoothing groups to separate polygons into different clusters that should have a kind of "fake smoothing" applied to them.


In a CAD program like MoI on the other hand, when you create a cylinder it is an actual cylinder spline surface. In a CAD program there isn't any "smoothing group" mechanism being used, things will look smooth if the actual NURBS surfaces are smooth, and creased if the NURBS surfaces are creased.

In that cylinder test file, the different NURBS surfaces are completely smooth to one another, so they are supposed to look smooth when rendered as well, despite them being in separate pieces. That's because the vertex normals in the file are supposed to be used for shading rather than just cooking up normals from the polygon faces.


> It does seem that MoIs files are different somehow.

It's not just MoI - it's stuff that is generated from any CAD program rather than a polygon modeling program.

CAD programs expect for a rendering program to use the vertex normals in the file to shade the objects, and not smoothing groups - smoothing groups should only be used for stuff coming from a poly modeling program and not a CAD program.


Note that in that same .zip file I also had an OBJ file saved from Rhino in addition to MoI - I thought you said that the Rhino file also showed the same segmented appearance problem in Octane as well?


EDIT: vodkamartini has described it more simply above as well.


- Michael