UV mapping is the process of projecting a 2D image texture onto a 3D object. Typically, such a texture is applied after a model, or body, is created.
They are many ways to give an object a look, either using a ready-made material through add-ons or creating custom materials in Blender. UV mapping can be used while creating a new material. And just to clarify, the material affects the object, while the UV mapping only affects the surface of the material.
In this article, we will explain the ins and outs of UV mapping in Blender. And if you need some resources to start with Blender, we’ve got you covered.
First, create an object. For simplicity’s sake, we can just use the default Blender cube.
Select the object you want to apply the material to, navigate to the “Materials” tab (usually located on the top right menu), and click “Use Nodes”. The default diffuse material will appear, and here you can choose the material you want to apply to the object.
The next step will be to add an image texture as the base color, and you can do this from the menu itself either by choosing “Image Texture” or by adding this node in the node editor. Once in, click it and you will be taken to your computer’s file directory. From there, choose the image texture you want to apply to the object. You may notice that it doesn’t properly show on the object. But don’t worry, we still need to do one thing…
By default, Blender launches in object mode. Click the “Object Mode” button located on the bottom bar and choose “Edit Mode”. Once in edit mode, hit ‘A’ on your keyboard to select all the vertices (or do so manually). With all the vertices selected, click the ‘U’ key (short for Unwrap) and many options will be displayed.
Click “Unwrap” and the object should be unwrapped. Another popular way is to use the Smart UV Project when clicking the ‘U’ to unwrap an object. Some settings will be displayed (we’ll leave them as their defaults) and the object will be unwrapped automatically.
Unwrapping Types Compared
The fastest and easiest way to automatically unwrap an object is by choosing the “Smart UV Project” option when unwrapping.
Blender will automatically cut the object into pieces and place them into the 2D texture plane. This method works fine in most cases, but sometimes there will be visible mistakes that you will want to fix.
In truth, the most reliable way to accurately produce a UV map from an object is to do the unwrapping manually. But don’t worry, it’s not as hard as it may sound. For this, we will use the normal unwrap method, but before we select the entire object and click “Unwrap”, we will need to mark some seams.
When you unwrap an object, you’re basically cutting that object into pieces and sticking them flat on a plane. You can picture this as trying to make a 3D cube from a piece of paper: you would cut the shape, then fold it until you made a cube. Then you could unfold it again, leaving it flat. Marking seams is very similar – you are basically cutting the model into pieces to then be placed flat on a 2D UV plane.
To do this in Blender, go to “Edit Mode”, as explained earlier, and select the parts of the model you want to make a seam at. But wait – which parts of the model should be marked as seams?
How to Mark Seams
There will be parts of the model where the texture will be “continuous” and “discontinuous”. This means that you will be able to see a sharp change from the texture where the cuts have been made.
Why does this happen? Although in the model, all the pieces are joined together, in the 2D UV plane, the pieces are all spread out, so they’re in different parts of the texture. Each one will show the part of the texture that corresponds to their positioning on the 2D UV plane, despite their place on the model.
You will want to make the seams on parts of the model where they won’t be very noticeable, such as edges. Do this by selecting the vertices on the model you want to mark as seams, hit Ctrl + E to open the edge tab, select “Mark Seam”, and repeat for all the vertices in the model you want to mark as seams.
Once you’re done, click ‘U’ and select the “Unwrap” option. Now, your model should be unwrapped.
Even after all this hard work, there are still things that we can improve from our UV mapping.
To see the UV plane, locate the bottom left bar and select “UV/Image Editor” while in edit mode. You should see the 2D pieces of your model mapped onto the 2D plane. This is a good tool in Blender to check the texture isn’t stretched or distorted.
Click ‘N’ while on the “UV/Image Editor” to bring up the toolbar. Under the “Display” option, there will be a checkbox called “Stretched”. Upon clicking it, Blender will apply a heat map over the image editor to show you where the UV is being stretched.
If everything is blue, it means that there is no stretching and the texture will show perfectly on the model, but if they are areas of light blue towards red, it means that those parts are stretched and will need to be unwrapped again with more seams.
To conclude, we would like to mention some things you can do with the texture.
While in the UV/image editor, you can select parts of the UV and move them, for example if you want them to be placed differently. Going to the “Textures” menu (just beside the “Materials” menu), under “Mapping”, you will be able to change the position, rotation, and scale of the image texture. In Blender 2.8, you might have to do this manually under the “Node Editor”.
Feature image source: FileSilo
License: The text of "Blender: UV Mapping – Simply Explained" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.