This is a Pro only feature.
The 3DS Export Options dialog box contains options for exporting 3DS files.
The Geometry section of the 3DS Export Options dialog box contains options for determining how geometry will be represented in a 3DS file.
Export (Full hierarchy)
The Export (Full hierarchy) option is used to create meshes for each top level nested component and group and, additionally, meshes for non-grouped entities based on the connection of faces. These meshes will be organized based on where they fit in the component and group hierarchy. This option allows you (using a tree view in AutoDesk 3DS Max, for example) to select individual components and groups with all their children and each connected face set as separate meshes. This option preserves the name of the component or group using the following rule for components: if an instance name exists, that name will be used; if an instance name does not exist, the definition name will be used.
Export (By layer)
The Export (By layer) option is used to create separate meshes based on a combination of how faces are connected and what layer (from SketchUp) they are on. All faces that are connected and are on the same layer will be grouped together in separate meshes. These meshes will then be organized based on the layer to which they belong. This option allows you (using a tree view in AutoDesk 3DS Max, for example) to select all objects on a layer using the organization scheme and then to drill down and select individual meshes within that layer. No hierarchy will be created with this option.
Export (By material)
The Export (By material) option is used to create separate meshes based on a combination of how faces are connected and what material they have. All faces that are connected and have the same material will be grouped together in separate meshes. These meshes will then be organized based on their materials. This option allows you (using a tree view in AutoDesk 3DS Max, for example) to select all objects with the same material using the organization scheme and then to drill down and select individual meshes having that material. No hierarchy will be created with this option.
Export (Single Object)
The Export (Single object) item is used to export your SketchUp model as a single 3DS mesh. This single mesh will be simple to select and manipulate once imported into another application. Because there is a limitation in the 3DS format that meshes can only have 65,536 vertices and faces, if this limit is exceeded, more than one mesh will be created with emphasis on keeping the number of meshes to the minimum amount necessary.
Export only current selection
The Export only current selection checkbox is used to export the currently selected geometry. The entire SketchUp model is exported when there is no selection. Additionally, the entire model is exported when this checkbox is not checked.
Export two-sided faces
The Export two-sided faces checkbox is used to export faces twice, once for the front and once for the back. This option doubles the number of polygons in the resulting 3DS file and can slow down rendering. However, this option ensures that your model will appear more like it appears in SketchUp. Both faces will always render, and materials applied to front and back faces are preserved. When this option is selected, SketchUp will weld the vertices of the front faces together and the vertices of the back faces together according to the logic for texture mapping and welding outlined in the following Export texture maps option.
Export standalone edges
Standalone line entities (lines not connected to any faces) are somewhat unique to SketchUp and not supported by many other 3D programs or the 3DS format. The Export standalone edges check box creates very thin rectangles that appear as standalone lines in the 3DS files. Unfortunately, this option can result in invalid texture coordinates requiring UV mapping to be re-applied before the scene is rendered. Also, certain exported standalone edge geometries can create invalid 3DS files altogether. The VRML format may better suit your needs if you need to export standalone edges.
Export Texture Maps
The Export texture maps checkbox is used to assign texture maps to 3DS materials whenever the corresponding SketchUp material uses a texture image. The 3DS format allows only one UV mapping coordinate per vertex, meaning you can not have a different UV mapping on two faces that share the same vertex. Given this limitation of the 3DS format, a tradeoff between preserving texture coordinates and welding geometry is sometimes necessary and reflected in the following two sub-options: Favor Preserving texture coordinates and Favor Welding Vertices.
Favor (Preserving Texture Coordinates)
When the Preserving texture coordinates option is selected, and UV mappings are different, the exporter breaks up geometry so that each coplanar group of polygons has its own set of vertices. In this case, vertices will not be welded together and no smoothing of faces will be evident. If UV mappings are identical, vertices will be welded.
Favor (Welding Vertices)
When the Welding Vertices option is selected, the exporter will weld together vertices which will keep your geometry intact and allow smoothing to be preserved. However, when two faces share the same vertex but have different UV mappings, this option will only allow one of the texture mappings to be preserved.
Use 'Color by Layer' Materials
The 3DS file format does not support layers directly. The Use 'Color by Layer' Materials checkbox is used to assign 3DS materials based on your model's layer assignments in SketchUp. Check this checkbox to export materials based on layers, such as when exporting to other rendering applications.
Generate Cameras From Scenes
The Generate Cameras from Scenes checkbox is used to create a camera for the default view as well as any SketchUp Scenes which have been defined. The current SketchUp view is exported with the name 'Default Camera,' and other Scene camera definitions are output using their Scene Name.
The units drop-down list is used to determine the unit size in the 3DS output.