Meshlab v1.2.2 is free open source software, dedicated to reducing big high-poly 3D models down into something that iClone can manage more easily in real-time.
Reading the MeshLab front page, it looks pretty daunting and techie. It isn’t really.
1. Launch MeshLab. Open your high-poly OBJ file (or other formats — 3DS, DAE, etc).
2. If it asks if you want to “unify verts”, say “Oh, Yes, of course! I knew that.”
3. Go to Filter / Remeshing > Quadric Edge collapse decimation.
4. Specify the “face count” (aka “polygon count”) you want to reduce to. Be sure “preserve normal” is checked when you reduce.
5. Click “Apply. Hey, I know what I’m doing!”
6. Save the reduced model out as an OBJ, or any other format MeshLab supports. 3DS format is probably best for iClone’s 3DXChange.
Congratulations. You are now an official Low-Poly 3D Model God!