Hi,
I'm completely new to CC3 and iClone and just bought it a couple days ago.  This community was amazing helping me with an issue before buying and I hope you'll have an answer for this one too.
I've followed this tutorial:
https://www.youtube.com/watch?v=nsE5qJP2xAI
in which a Reallusion obj shirt posted on Sketchfab is importet as an asset into CC3.  That's all good.
Then I had the great idea of wanting to put a logo into the shirt and maybe changing the cloth texture, so I took the obj into 3DCoat, put my logo and some dirt on and exported it.  Now wehn taking it into CC3 the poly resolution is very low though I did not modify the geometry.
I tried a pass through Hexagon and another pass through e-on Vue.  All the same.  The moment the obj passes through another application it imports into CC3 in a very low resolution.  I can smooth it in Hexagon by adding geometry but I have to add so much that CC3 slows down notably.  I also tried fbx (not from Hexagon).
I'm attatching a picture showing the same shirt.  The gray one is Sketchfab straight into CC3, the White one is Sketchfab - 3dCoat - CC3.  I'm guessing there is a trick to this that I'm not aware of.  Thank you in advance for any advice!!

Resolution looks fine. Mesh just needs smoothing, or rather fixing doubles. Somehow you managed to sharpen (doubled) the mesh edges in 3DCoat (at least that is how it appears).
Otherwise, if you did not change the UV in 3DCoat, you can save yourself a trouble and apply textures generated by 3DCoat to the existed t-shirt.

BTW, you can do decals, dirt and more right there in CC without the need to take it out to 3rd party apps. Use Appearance Editor for that.

All meshes are built of polygons. The smooth appearance is just a rendering trick of how the light plays over the facets. You can adjust what is called the "Normal Smoothing Angle" to make your mesh appear smooth. This is how all 3D apps work. See here:
https://manual.reallusion.com/Character_Creator_3/ENU/3/Content/Character_Creator_3/3/04_Modify_Menu/Edit_Normal/Auto_Smoothing_Mesh_Nodes.htm

Thank you both for the replies and the link! I think I understand what’s happening. This is all quite new to me and with something like this I wasn’t even sure how to search google for an answer.
Once again thank you!!