UV Mapping with 3DS Max

01. UV Mapping Overview

In this section we’ll go over UV unwrapping workflows. UV unwrapping is the process of taking a 3D model and unfolding it flat so that we can paint on it, like a picture. It’s like taking a shirt that’s already been made and unfolding it to the original flat pattern, or taking a globe and turning it into a 2D map.

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02. Basic UV Terminology

In UV mapping, we take a 3D object and unfold it flat. Our main goal is to do this with the minimum amount of distortion. To do this we have to split the 3D model in different locations to allow it to relax properly. These splits are called seams. [2]

For example in the image above a globe has been unfolded flat in two ways. The projection on the left is less distorted (notice how small Greenland, Antarctica, and Europe are) but it has more seams meaning that it’s harder to paint continuous detail across. The projection on the right has no seams but is much more distorted.

In the 3DS Max, seams are shown as green lines on the model. Notice however that on the 3D model a seam will appear as only one edge. In the UV space this same edge will appear in two different places because it has been split.

Once a model has been split up it will often be broken into different separate chunks called UV Shells or UV Islands. This is often necessary for objects that are projected on completely different axis (like the top and bottom of a cylinder vs. the side of the cylinder) or are completely separate elements.

Finally a texel is a single pixel (dot of color) on a texture map that has been applied to a 3D model. If you have a very large UV island then your texels will be very small. If you have a very small UV island then your texels will be very large. At Wayfair, we want all the pieces of your model to have a uniform texel density. You can see this when a checker pattern is applied to your model. If the checkerboard is the same size on all the different parts of the model and all the checkers are square then you have a uniform texel density. In the image on the left below, the texel density on the top of the barrel is very high but on the sides the texels are very stretched out, showing a low texel density. In the image on the right both the top and the bottom of the barrel have uniform density.

03. Projection Methods

There are multiple ways to project a UV map automatically using standard geometric projections (project via box, sphere, cylinder, etc.). 3DS Max has two ways of interacting with these projections – the first is with the UVW Map Modifier and the second is the Unwrap UVW Modifier.

For details on how to use the UVW Map Modifier you can watch this video (LinkedIn Learning). For details on what each option in the modifier does you can read these help files (Autodesk).

However at Wayfair we recommend using only the Unwrap UVW Modifier. This modifier has all the same automatic projection options as UVW Map (except “Shrink Wrapping” which is rarely used) but it also has many more and allows you to manually edit the UV projections. For information on how to use the Unwrap UVW Modifier you can watch this video (Cellygon) and read these help files (Autodesk).

Once you are in the Unwrap UVW Modifier you will be spending a lot of time in the Edit UVWs window.

Also see more detail on subsections in this Modifier by visiting these Autodesk Knowledge Base articles.

Within the Unwrap UVW Modifier there are a lot of automatic unwrapping options to help you unwrap your model more quickly. Take a look at this video (Autodesk) to learn how this is done. Some help files are available on unwrapping UVs by automatically selecting faces based on their direction using the “Normal Mapping” dialog in the UV editor. There is also an automatic tool called the “Flatten Mapping” tool which will automatically split apart your object’s UVs to minimize the amount of distortion. You can read about how to use it here.

Once your model is unwrapped you will want to eliminate stretching. This is done by “relaxing” the UVs which can be found in the “Relax Tool” dialogue box.

Other useful tools found within the Edit UVWs window:

UVW Editor Dialogs:

05. UV Channels

3D objects can have any number of UV maps applied to them by using UV Channels. While this is an advanced feature it is still important to understand that it is available. Both Unwrap UVW and UV Unwrap can use UV channels.

When you create a UV modifier it will automatically default to Map Channel 1. You can change which Map Channel you are creating UVs for by just changing this number. The Map Channel is referenced in the Coordinates rollout of a node in the Material Editor:

As you can see above, the Map Channel that this texture is using is Map Channel 1, so it is using the UVs that are in the Unwrap UVW Modifier in our example to the right.

Now, let’s say that I want to put a sticker on a wooden case. The case has already been properly unwrapped in Map Channel 1. If I want to add the sticker, I would create a flat projection of the front of the case in Map Channel 2 and assign the sticker material to use that channel.

For more information on how to use this feature you can watch this video (Denis Kozhar). Note that you may have to actually render your model to see the mixed textures applied.

04. Strategically Creating Seams

Hiding your UV seams is crucial to maintaining a realistic looking products. If your seam is visible then the separation between two different areas of the texture will become obvious and it will look like your model’s texture randomly stops in the middle of the surface. Below is an example of poor UV seams. Notice how the checker pattern is interrupted, rotated, and resized throughout due to randomly generated seams. The same thing would happen to an image applied to this model as a texture.

a. The link below is an example of strategically cutting seams on a simple model. Notice that the author selects areas where there are material breaks, large direction changes, or in areas that are not normally visible to the viewer. By doing this the modeler is able to hide those seam transitions using the natural geometry and materials of the object they are making.

b. Even though we don’t create many organic models, the tools shown here are the same ones we use to UV unwrap many of our more complex models. Notice how the author places seams in hard to see areas. Watching these tutorials is highly recommended.

06. Putting it all Together (Videos)

07. Troubleshooting Texture Stretching

  • Cut additional seams to create more individual UV shells and then relax each shell
  • Select polygons and break them apart into separate shells then relax each shell
  • Stitch broken edges back together after they’re properly relaxed
  • Flip inverted UVs
  • Make sure X Y and Z scale are at positive 100% before unwrapping. Reset XForm first if necessary.
  • Make sure there are no duplicate vertices before unwrapping

08. Unwrapping Exercise

  • Follow along with the guide to basic UV unwrapping here.
  • Afterwards you can follow along with the advanced UV Unwrapping tutorial here.
  • Finally once you have completed these tutorials you can take on the UV Unwrapping Exercise.
  • TODO: UPDATE Links above.