This is Conwy Castle in North Wales, sitting in the U4 editor.
It will be (along with some more of my models) present in the April release of the game "Battle Siege Royale" by Skjold Game Studios. Didn't they do a great job with the rocks at its base?
This is an excerpt from Volume II (still in writing) of the Modelling with Wings series. Please note: This is not the final draft as it will appear in the book so you might find the odd mistake ;)
Multiple
Object Mapping
In
many situations, your model is going to be made up of several
separately made parts.
In
the screenshot above, we have a simple model of some cogs and a
spindle made up of three
separate parts (elements) that we can select
and UV map, to produce three separate materials.
This
is all well and good, but what if we want to save on disk space/
download times, rendering
times, not to mention the confusion of
having four or five maps for each separate part of our finished
model.
To
fix these problems we would usually combine these elements with the
aim of producing one UV
map for all. This is often referred to as an
atlas map, or multi-texture map.
There
will be instances where this isn't possible, but wherever it is
possible, it should be done.
After
that quick explanation, let us get back to showing you how to do
this.
Above,
we have the UV maps of the three elements but they're all on separate
sheets. Our mission is
to merge them together on one sheet to make
life easier for everyone (especially you).
The first thing we need to do is “shift” the elements on each map so
they're not in the centre view
port.
To
do this we need to highlight everything on the map and move it over
to an empty space and out of
the main window as above.
You
then repeat this process for each separate UV map, moving the
elements in each one to a new
space that you haven't already used.
Ensure
you keep that centre viewport clear, you will thank me for it later.
Once you have done this
you can return to your model and right-click,
combine (in Body mode) to make your separate parts,
one whole,
object.
We're
not finished yet. We now need to assign a material to this new
singular object. With the model
highlighted, select any of the old
materials used for the previous separate UV maps and rename it to
something sensible that reflects your model or part of your model.
I'm just going to call mine
“Complete”.
You
can now delete any other materials that were associated with the
separate parts of the model as
they are no longer applicable to the
project.
With
your combined model selected, right-click on the “Complete”
material and “Assign to selected”.
This assigns one single
material to the entire model.
We
can now return to the UV map from the right-click menu and see what
we have;
All
three of the objects UV's are now incorporated into a single map.
What we now have to do is fit
them all into our centre viewport.
When
Wings unwrapped your original objects it sized all the faces so that
they would fit on a single
sheet. This means that your UV's may not
be equal in real-world sizes.
Just
in case that didn't make sense to you, imagine you mapped a screw
head, Wings would fit that
in the UV space at its maximum size. Now,
imagine you mapped the side of bus. Wings would fit
that
into the
same space as the screw head, which is all good until you combine
them, as we now have
two items that are completely disproportionate
to one another.
To
fix this problem Wings provides us with a simple solution.
Once
you have all your parts on that single UV map, select them all and
right-click, scale, normal
sizes.
This
will instantly give all the faces the correct proportions. Very
handy.
Using
just your eyes, you may now be wondering how all these elements are
to fit in this centre view
port without overlapping each other. This
is easy, we're going to guess.
With
everything still highlighted, right-click, scale-uniform, and scale
everything down until you think
you can fit it on the sheet. Once
you've done this, you can now arrange the separate faces on the
centre viewport by selecting them one by one and placing them
sensibly on the map.
If
you can arrange them in a way that makes your life easier when they
are to be textured. Ask
yourself some questions. Is the texture going
to be wood and have a direction grain? Will the texture
have text or
a logo on it? This pause for thought will save you a lot of time in
the future and is well
worth doing now.
If
for instance, you're using a wood-grained texture it would be wise to
rotate the parts so that the
grain would flow in the same direction.
It is also a good idea to place the parts that use the same texture
closer together, or grouped.
This
is especially welcome if you're using a program like Substance
Painter to make your textures,
as small faces can easily get lost in
the masking process, just ask Rod Stewart (sorry, Dad joke).
In
this modern age, I can not think of a reason why you wouldn't want to
be using PBR (Physics-
Based Rendering), so it is equally as important
that you do not overlap the faces on your UV map as
that will create
unwanted effects when placed into a game world.
As
you see below, I now have a single map containing my two cogs and the
spindle.
One
texture to work on and of course, keep track of is much better than
three, and also makes your
model more attractive to prospective
buyers.
This
won't always be possible because of resolution requirements, or the sheer
size of the model,
but where it is, you should be doing it.
Here is a video you can find on my channel that does something very similar to the above;