Books and Models by Simon T Griffiths

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they are no longer applicable to the project.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;