Hi thanks for your replies.
I had previously created a precise shape in grasshopper. Unfortunately I don't have the definition any more, but I had baked the object in rhino so I still have a .3dm and obj. file.
Today, I need to achieve boolean operations between this shape and other ones that I'm about to create with grasshopper.
That's why I tried to get this geometry back in grasshopper.
Is brep conversion, the only way to achieve intersection operations?
The local Code plug in seems to be handy.
I heard about an external component using t-splines to perform a mesh to brep component. http://www.tsplines.com/forum/viewtopic.php?f=9&t=29673
I do not own the t-splines plug-in at the moment, but before purchasing, I wonder if it's the right tool.
If you can get the obj file into rhino with the localcode plug in, here's a definition that does the rest of the job - takes a mesh and converts it to a brep with one surface per face, with results equivalent to the MeshtoNURB command.
If your goal is intersections however, you might have better luck simply performing mesh booleans - giant many-faceted polysurfaces like the ones produced by this definition are likely to be unwieldy.
Sorry, a tiny problem is still remaining. the converted brep does not seem to be closed.
how could I make it closed in order to use the brep volume component or make some intersections?
thanks one more time.
If the input mesh is closed, the resulting BRep also ought to be. Is this not the case? If you can upload the particular mesh you're using I can take a look.
If the openings remaining on the output BRep are planar, you can use the "cap" component to fill in the faces. Otherwise you are probably going to have to do some mesh editing directly in rhino before converting - FillMeshHoles, etc.