(Mesh model shown above created in AC3D and shown in Second Life by Clay)
Second Life now supports meshes, which means you can use
AC3D to put virtually any model into Second Life with great ease.
To export a model from AC3D and use it in Second Life,
export it as Collada. Collada files use .dae as a
file name extension e.g. car.dae.
In Second Life select menu Build->Upload->Model and
select your .dae file from where AC3D exported it.
Here you can name your model (here it is called .my car.).
Here you can define the Physics of the model (how it reacts to collisions, if
it.s solid etc). You can also provide alternate
models for levels-of-detail which determines what you see at different
distances.
If the model is texture-mapped, select the checkbox near the
bottom right, this will show a preview of your
textured model. Note that if you press 'Upload' now, the textures will not be
uploaded.
For textures to be uploaded, click on the 'Upload options'
tab and check the 'Upload textures' tick box.
Uploading aything costs Linden
Dollars. Uploading a model and texture will cost more than just the
model. Press the 'Calculate weights and fee' button to find out how much
it will cost.
After uploading, your model appears inside your Inventory:
Simply drag it from here into your world (in which you must
have building permission). Then you can position and scale your model as
needed.
There are other options available when uploading models, see
the official Second Life Uploading a Mesh Model page for more detailed info.