ISSUE
After importing OBJ is black. This was happening until Rhino 6 SR25. Now fixed in new Rh vr.
Sometimes when you are exporting and importing the object by using OBJ,
the 3D object turns into black.
Why?
Because there is no material applied to the object that you what to export. If there is no material in the layer, the OBJ exporter will apply the layer color. The “Default” layer is black. So the exporter is making a black material. Since the material is flat it looks like a bug. But it is not. If you select the mesh and you look into the material, you will see there is a new material with black color applied to it.
SOLUTION
Now in Rhino 6 SR26, there will be a new toggle additional option in the OBJ export options. Will prevent exporting the layer color. And the imported color will be white the same as FBX, IGES, etc.
Why OBJ is not exporting my layer color?
If you are using the color of the layer as a material color then enable this option (On).