Welcome Mister E ! Please see the following tutorial for the recommended procedure

http://www.3drad.com/interior.php

Mister E. The tutorial is good - if you can remember everything and have 2 computers - one to follow the tutorial and the other to do it in 3DRad

For simple things such as buildings etc - this is what I do:

1) Find what you want
2) If you want it to be a rigid body (for collisions for example) then first scale the model to the exact size you want. If you don't do that, and you want to change the size in 3Drad later, you will need to use a sphere shape for collision.
3) Once scaled, move the object to the middle of the 3 axis, sitting on the RED line.
4) SAVE the model as a SKP (File..Save As..)
5) Go to Plugins and Export the model as an untextured Rigidbody. If there are lots of elements that may take a few moments.
6) Without moving anything, go back to Plugins and export either as a Skinmesh, or Skinmesh with Backfaces.
7) Place the Rigidbody in your project, then without moving anything, add your skinmesk to sit on top of it.

If you just want a Skinmesh you don't need to scale the model in Sketchup because you can rescale in 3Drad without any problems. You only need to scale it if you want a Rigidbody that will collide with THAT shape of model.

Hope that helps.

Edit: Be warned - not all colours and textures are exported to 3Drad as you see them in Sketchup. Keep it simple and it will work well. Here is an example of what I did from Sketchup.

Sometimes you may not need the Rigidbody PLUS the Skinmesh (if you do not need to look underneath of the Rigidbody or walk inside of it for example).

If that is the case then just export the Rigidbody with the textures.

If you do need a Skinmesh with the RB then be sure to export the RB as an Untextured RB.

Have fun Mister E 

Hi Mr E,

I wouldn't know how to do this directly from Truespace. However, this is what I usually do since I am using Sketchup and Truespace both:

Create your model/shape in Truespace, and save it as an DXF/DWG autocad file or even OBJ file.
For the OBJ file plugin: http://sketchuptips.blogspot.com/2006/12/plugin-obj-importer.phpl
For DXF/DWG import just go (in Sketchup) to File>IMport and choose the Autocad format.

The only problem saving it as a DXF//DWG is that you will loose your textures since all you are exporting using this format is the geometry, so you will have to retexture your model in sketchup.
Not too sure about the OBJ format to be honest, I think that will allow you to keep your textures.

Like I said you can make your sphere or model in truespace, export it to one of the above formats so you could continue working on your model in Sketchup!
Once you are done in Sketchup, you could use the 3Drad exporter in Sketchup to create a Skinmesh.
Btw, there is a way to create spheres in Sketchup:
http://sketchuptips.blogspot.com/2006/12/sphere-tool.phpl

Download the RB file and place it in your Sketchup plugin folder and voila....!