Custom assets and objects for map making?

[Argoon]

You need to divide your model in submeshs just like Thomas said and assign a material to the meshs with the texture that you wan't, them open the .dae file on the model editor and them click on "View - outline" a small window will come up showing the names of the individual meshs on your model, click on on a name and that mesh will become selected and outlined on the 3d view, them on the right side click on the material option and chose a material to assign to the model, you can assign a existing material or one made by you.

i was able to open a simple "map" on the model viewer and assign material to it but the model is gigantic, it is 3 meters high on my 3d app but on the model editor it seams to be 30meters or more.

I tried to edit the collada file by changing the meter value and no mater what i assigned the model is still very big.