Things You'll Need
Instructions
Cloning an Object
Click on "Create New Project" and select the appropriate category ("Hair," "Accessory," "Object") from the next pop-up dialog.
Select an object to clone as your reference object. Pick something as close in possible in shape to the object you want to create to minimize the work. You could technically create a barstool using a bed, for example, but it will be more difficult to create the final mesh. Click "Next."
Fill in "Project Name" with a unique name that's different from any other object in the game, even ones designed by other creators. The object creation tutorial at The Sims Resource recommends a format such as "creatorname_objectname_date_time".
Fill in "Title" and "Description." These will appear to players so should be descriptive. Click "Next," and then click "OK" on the final dialog.
Save the project as a .wks file as a reference for your new mesh.
Click on the Mesh tab to see your levels of detail, or LODs. Pick one LOD and then click on the Export button, which looks like folders with a red arrow pointing away. This will export the mesh as a .wso file. Do this for each LOD, giving each a separate file name.
Editing The Mesh
Create your new mesh using either MilkShape or another 3D modeling program. You can use the original object as a starting point or create a new mesh from scratch.
Optimize the poly count. Too many polys and the object will slow down the game, but too few and it will look crude and unfinished. When in doubt, keep the total the same as the reference object. MilkShape users can use the software's DirectX Mesh Tools to optimize poly counts. Other 3D modeling software may have its own optimization tools.
Open the mesh in MilkShape--you must use MilkShape for this step--and then select File > Import > TSRW Object. Select one of the .wso files you exported from TSRW. You should now have two meshes displayed: the reference object and your new object.
Click on the Bones tab. If no bones are listed, skip this step. Otherwise, click on each bone and then on "SelAssigned." If the original object lights up, that bone is attached to that object. Double click on your new object, then on the bone name, then on "Assign" to assign the bone to your new object. Export as a new .wso file.
Repeat Steps 3 and 4 with each .wso file exported from TSRW.
Finishing Your Object
From TSRW, click the Import button located next to the Export button that you used before. Select one of the .wso files that you exported from MilkShape to be sure it displays correctly.
Click on the Auto Generate Sun Shadows button, located next to the Import button. It has the symbol of two arrows in a circle. This will automatically generate the proper shadow mesh for your new object.
Save your new meshes. You will still need to create UV maps, bump maps and textures and then merge all of these resources in TSRW to create your final object.