Maya: Importing from Rhino and Nurbs to Polygons

In this tutorial we will cover the workflow for moving from Rhino into Maya and the conversion of nurbs surfaces modeled in Rhino into polygon meshes in Maya.  Maya works well with Rhino, as they both share a true nurbs modeling package.  Maya also offers a more comprehensive polygon modeling package to Rhino which allows for quick modeling on formal and massing studies.  It also can assist in the production of clean 3d print files.  Also, converting to polys in Maya allows more intuitive control of tessellation than Rhino's mesh from Nurbs tool.

To begin I will model a simple surface in Rhino and then export it using the ".igs" file format.

In order to import it into Maya I will need to go to the plugin menu and turn on the neccessary plugins.  In order to conserve memory, Maya will only turn on a minimum of plugins by default.  However once your plugins are set, they will open by default every time you use that copy of Maya.  To turn on the neccessary plugins go to the "window" menu on the tool bar, "Settings/Preferences", and then "Plugin Manager"(window>Settings/Preferences>Plugin Manager).  A window like the one below should appear.  Turn on "DirectConnect.mll" and "DCExport.mll".  Be sure to click on Auto load as well so that these plugins will load automatically in the future.

Next we need to go to the "File" menu, scroll down to "Import" and go to the options menu for import by clicking on the box next the Import Command.  A window like the one below should open up.  Under "File type:" menu, drag down to IGES_DC then click import and using the explorer find the file you exported from Rhino.

If you compare the above surface to the one we had in Rhino, you can see that it has the same construction, which will allow us to be precise when making our conversions and plan ahead when working through different phases of a project.  For example we will now convert our Nurbs surface into a polygon model, directly translating our isoCurve layout into quadrilateral mesh faces.

I duplicated my surface in order to allow us to compare the Nurbs original to the new Poly version.  To convert our surface, select our surface then under the "Modify" menu on the tool bar go to "Convert" then "Nurbs to Polygon" and open the options by clicking on the box next to the tool (Modify>Convert>Nurbs to Polygon).  This should open a window like the one below.  I have set my tesselation "type" to "Quads" and my "tesselation method" to "General".  In the "Initial Tesselation Control" section I set my U and V type to "Per Span # of IsoParms" and my U/V numbers to 1.  I will leave the Secondary Controls unchecked.  By hitting apply you can see the new Poly geometry (below) and compare it to the base Nurbs surface (above).  the polygon's vertices are now located directly at the Nurbs isoCurve intersections.

By meshing the surface this way we have a clean polygon geometry with continuous quad loops that can easily move back and forth between Maya and Rhino in an intuitive manner.  I will now run through a few Polygon operations to highlight some of the advantages to working with a Poly model in early formal studies (a more in depth explanation of these tools will be given in the Explicit Modeling tutorial).

First I am going to duplicate my mesh, scale the copy by -1 across the x axis, and bridge two of the faces together.  The bridge geometry is a difficult thing to model in Nurbs surfaces, requiring it to be constructed with surface patches, trims or t-splines.

From here I am going to stack a few modifiers together to approximate the panelization definition we created in our Grasshopper tutorial.  Since we are not going to be developing the panel component from scratch, we are more limited in terms of its output, but this will allow us to quickly test a truss like surface condition in 4 quick steps.

First I will use the add division tool under "edit meshes" set to triangles to create the center point triangle subdivisions.

Next we will use the extrude tool under edit meshes to offset in the frames and then delete the highlighted faces to create openings.

I will extrude the mesh again, this time with the keep faces together option clicked on to give it thickness, then smooth the mesh to produce a final geometry similar to the one we produced with grasshopper.