How to export from igs/step/stl/ipt to c4d and obj ?
As Maxon'ss CAD conversion provider for the last 18 years this is the one and only technically correct + native way to achieve such conversions, which will always be 100% error free:
But as the main question I ask of everyone each hour, from which MCAD program is your data coming from? Above all, everyone always comes to me with the same question "How do I convert IGES and STEP to C4D". However, that is not always what you want to do, as that is the least common denominator file format. Also, 80% of world-wide people always end up using the obsolete and deprecated 1995-era IGES file format, which is the #1 epidemic problem. Your list does mention Autodesk Inventor but statistically 90% of people on this planet would source their files from ProE/Creo or SolidWorks, with Inventor being in third place. Hence, most importantly, you should find out the name of the MCAD program from which the files are coming from and only then determine the proper method to source from that program. For example, with Inventor, you would logically only want to source via native Inventor files or DWF-3D, and never IGES or STEP. Also, as another terrible misconception seen in forums, you never want to touch STL ever in your life as there is no other file format worse than STL. If you are using STL for any conversions then you really don't know much about 3D data translation - a good STEP AP214 file, or a DWF-3D file, will do you 100x better than using STL.
Hence, once you find the name of the source MCAD program then all the other pieces of the conversion puzzle falls into place immediately.
On OS-X at least, read STEP/STP in to the free (open source) CAD Assistant (https://www.opencascade.com/content/cad-assistant) and use the floppy disk icon on left to save as ply (w/ colors) or obj (w/ mtl). Also check out the cool "Clipping plane" feature (bottom icon on left).
If you want to colorize first, use FreeCAD and http://sliptonic.com/freecad-hidden-gems-setting-colors-for-individual-faces/, save as STEP w/ color and follow instructions above.
All free & open source.