what i got so far, i hope it helps others. you can edit USD, OBJ and DAE files to add extra uv channels manually. not ideal but you can. all of them involve having duplicate geometry each with the set of uv channels you want to merge the easiest to change is the USD file. open file in text editor and copy these 2 sections from the other mesh objects texCoord2f[] primvars:st int[] primvars:st:indices paste those in the mesh object you want to add them to. they will need unique variable names, i just add numbers like this texCoord2f[] primvars:st2 int[] primvars:st2:indices save file and done for OBJs there is only one section per map but there are more numbers to change you'll want to copy the section "# 88 texture coordinates", the lines look like this and there are many of them, vt 0.419371 0.134602 0.000000 vt 0.410308 0.142855 0.000000 paste that at the end of the mesh and change the vt to be unique for every texture map like this, vt2 0.419371 0.134602 0.000000 vt2 0.410308 0.142855 0.000000 DAE files are the most versatile but harder to judge how the maps relate. as with USD there are 2 sets to copy but sectioned of in tags

edit. i tried reality converter with an FBX with multiple UVs and it too ignores them all and just keeps 1.

how is your model built? what are we looking at? where is the material applied? what do your UVs look like?

you can make the same type of games but the same functionality provided by unity out of the box won't be in scenekit.

"Isn't this need part of what Reality Converter was built for - to go from .obj to .usdz?" but i'm not trying to make usdz files. i'm trying to figure out why OBJ files in scenekit are blank.

so i figured out the pivot getting moved in dae files. but i still wish i could open obj files as it would make my world easier in general