Hi Jeongho,

This looks like a smoothing group problem. Unfortunately 3dsmax does not seem to import vertex normal smoothing information when it reads in an .obj file (unfortunately including that guruware importer I guess).

Instead it looks there like it is trying to automatically guess at how to smooth the object by using angles between polygons. That tends to be prone to cause shading glitches when you have larger polygons next to smaller polygons.

It would be much better if it didn't try to do this kind of angle-based guessing and instead use the smoothing information already inside the .obj file. Other programs that use that smoothing information (for example, Modo, Cinema4D, XSI, Maya) will not have those kinds of shading errors and will show a nicely smooth render off of that exact same data.

This has been a very long standing problem with Max and also LightWave, they have never seemed to modernize this particular area of their programs. Here is some other information on it: http://www.okino.com/faqs_output_dir/12.htm#9

If you can see an option in the importer that says "use vertex normals" or something like that, try enabling that to see if you get better results.

Also if you have an option for "smoothing angle" you may try raising that to a higher angle value.

You wrote:
> To avoid this, should I increase mesh count?

Yes, it should help, if you have polygons that are more of a smaller even size it will make the angular/averaging type smoothing group processing work better. There was a recent post on how to dice things up into smaller bits:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1549.4

- Michael