Solution to improve performance (to increas the speed) when opening PDF file with large 3d model?

Question

I insert a large .u3d building model into PDF file(more than 40M .pdf file), very slow when opening it (more than 30 minutes). Is there any way to improve this when creating the PDF file? It is acceptable to reduce the precision of the model shape/color/texture when inserting it into PDF. I think my hardware is OK,THINKPAD 520 with 8G RAM. This is urgent for me. For any solutions or clues, please let me know.
Thanks and best regards.
MD

Answer 1

All of this quite old stuff
http://www.okino.com/conv/exp_u3d.htm
PDF Publishing - 3D PDF and PRC | Tech Soft 3D
http://www.3d-test.com/contenu.php?id=317
http://wiki.david-3d.com/_media/user_page/magweb/judasml1.pdf
in the end, I would try
CAD => PRC
CAD => OBJ => Blender/MeshLab/... OBJ compression => U3D
CAD to OBJ conversion can be done outside but it should be best done within the CAD authoring application (I would leave compression level to a minimum here); I say that because this is what a powerful conversion tool such as Okino states about CAD Data
As mentioned in the "NOTES" above, imported CAD data is most often in a form whereby it mainly consists of triangles, and those triangles can tend to be long sliver triangles due to the "trimming holes" in the source NURBS or BREP solids objects. Also, CAD data tends to have an over-abundance of polygons due to high tessellation of the source data. The Intel MultiRes compression algorithm cannot handle this case of sliver triangles too well (or an overabundance of very small polygons) very well, and hence compression should be reduced or minimized for such CAD datasets. CAD data also tends to have a lot of sharp angular features and thus the "vertex normals" exported and compressed into the U3D file must remain untouched -- too much vertex normal compression leads to a lot of "black banding".
Blender/MeshLab/... OBJ compression is not straightforward; see "quadric edge collapse decimation" in MeshLab but there are lots of alternatives...
(you should try to replicate yourself what the Acrobat 3D Toolkit once did: Optimizing file import for Acrobat 3D Toolkit - YouTube - maybe you can check if Tetra4D tools do it; Tetra4D took over Acrobat 3D business for Adobe)
in the past, I also used Rhino and SALOME to compress CAD to OBJ (SALOME to STL) but I wouldn't recommend this way
MeshLab/SimLab/Okino/... can save OBJ to U3D