Use single sided meshes

New meshes in blender are double sided by default. The exporter will add backwards facing triangles to achieve the double sided effect, doubling your triangle count upon export.  To set a mesh as single sided:

1. Switch the 3d view into object mode and select the mesh.
2. Under the buttons window, editing buttons (F9), you should see a "Mesh" panel. Toggle the "Double Sided" button to the off state.

See also:

• DTS Meshes - Double Sided Meshes
• Blender Survival Guide - Setting Meshes as single sided

Use Smooth Shading on meshes

New meshes in Blender are set to use Solid Shading by default. Solid shaded meshes have a blocky or faceted appearance when lit. The exporter reproduces this effect in your exported models by doubling up the vertices along shared edges, so that each non-coplanar face has unique vertices with their own vertex normals. Having all faces set to Solid Shading can double or even triple the number of vertices for a given set of triangles (exact count depends on mesh topography). If you hit the vertex index limit too soon, try setting all faces in your mesh to Smooth shaded. This is done as follows:

1. Select your mesh in object mode.
2. Under the Link and Materials panel of the Editing buttons (button window, F9), press the "Set Smooth" Button.

Note: Individual faces within a mesh can be set to smooth or solid shaded by using the "Set Smooth" or "Set Solid" button while the faces are selected in edit mode; but only if the faces have a blender material assigned to them.

See Also:

• DTS Meshes - Vertex Normals
• Blender Survival Guide - Setting mesh shading modes

Split up large meshes into separate mesh objects

Split large meshes up into multiple mesh objects, each one having fewer than 10900 triangles:

1. Select your mesh and switch the 3d view into edit mode.
2. Select the faces that you wish to split off into a separate mesh.
3. Press 'P' and choose "Selected" from the "Separate" menu that appears.
4. Rename the newly created mesh object if desired.

Decimate meshes (Polygon Reducer script)

The triangle count on a mesh can be reduced by running the "Polygon Reducer" script that is included with Blender:

1. Open up a scripts window and click Scripts->Mesh->Poly Reducer.
2. Adjust the "Poly Reduce" setting, then click the "OK" button on the right-hand side of the poly reducer script popup.

Manual Mesh Decimation using Blender's Retopo tool

The re-topo tool allows you to draw new vertices and faces on top of an existing mesh (they snap to the underlying surface). This is very useful for converting high polygon count models into lower poly versions (but a bit time consuming):

www.blender.org/development/release-logs/blender-243/retopo/
www.blendernation.com/2007/01/15/retopology-tool-tutorial-and-video/