The Artifact is ready to unleash its hellish power! However, it doesn't really look like much with its default grey exterior. Just like we did in Chapter 3, It's Time to Customize! we need to UV Unwrap it so that we can create a material for it and bring it into Unreal. Unlike our crate, the Artifact is a much more complex object and is made of multiple smaller objects. This will require us to use a different technique to create the UV map and for that we need some different tools. Rather than use the Smart UV Project option, we will use custom seams to flatten out the different sections of the Artifact. In this chapter, we will cover the following topics:
- Unwrapping complex objects
- Custom seams and the Unwrap tool
- Using Smart UV Project along with other mapping tools
- Using different types of texture maps together, to create a more realistic look
Back in Chapter 3, It's Time to Customize!, we learned a simple technique for UV unwrapping called Smart UV Project, a tool that can unwrap simple objects automatically. This process worked great for our crate, but the crate was little more than a slightly modified box. The crate really didn't have much in the way of curves and its triangle count only reached 516. The Artifact will take a little bit more work to unwrap. Our new asset contains 42 separate pieces and has a whopping 54,000 triangles. To unwrap this monstrous game asset, we will need to apply several new tools and techniques.
Seams are lines along which Unwrap tool can slice an object to flatten it out during the unwrapping process:
Using custom seams to UV Unwrap a basic cube
Using the Mark Seam tool, we can control which lines becomes seams, giving us complete control of the process. We can also use this tool to hide our seams in places a player will not be able to see them. This can be along areas that are normally hidden, along sharp angles or creases, and in areas where the material we are using changes dramatically.
Unwrap tells Blender to mash our object flat, splitting at the custom seams we have marked
After making our seams, we need to tell Blender to flatten out our object. This is done using the Angle Based Unwrap tool, or simply the Unwrap tool. Unwrap takes our seams and treats them like cuts in a cardboard box, then mashes our object flat. The results aren't always perfect. However, Blender has several other tools that can fix these minor issues.
Stitch allows us to fix some errors that the Unwrap tool may have created
Sometimes when marking seams and using the Unwrap tool, we may wish to reconnect a couple of faces in our UV map, such as when a seam looks obvious after we place a material on an object and we would like to move it. The Stitch tool can be found in the UV menu of the UV Unwrap window. Using it is a two-step process. After moving two UV islands (a collection of faces that are connected together in a UV map) that have a shared edge close to each other, we can check whether two faces have shared edges by clicking on an edge in the UV map and looking to see where another orange highlight appears. If you click one edge, another highlights as well; those two edges can be stitched. After lining up the edges, head to the UV menu and select Stitch, or press the V key. Once the tool is on, we have a few options. The Tab key changes whether we are stitching in edge mode or vertex mode. The S key turns the Snap mode on and off. Snapping will snap the UV island that was first selected to the island that was selected second. We can also choose to stitch the islands at their midpoint, by pressing M and turning on the Midpoint option. Finally, pressing the I key will swap which island will move during stitching. Once we have the settings the way we would like, pressing Enter will finalize the stitch.
Average Island Scale can be found in the UV menu
Sometimes when unwrapping a complex object, the unwrapping process will create UV islands that are out of scale with the rest of the map. Average Island Scale can restore even scaling to UV islands, which will minimize stretching and blurring across the textured area. Simply select the UV islands you wish to average, select the UVs menu at the bottom of the UV Unwrap window, and select Average Island Scaling or press Ctrl + A.
Pack Islands will attempt to arrange and scale your UV islands to achieve the best results
Once we have arranged all of our UV islands, we can use the Pack Islands tool and Blender will automatically arrange and scale them to best fit the UV space. This is a great tool to finalize our UV map and get the most out of Blender's UV space. We will use this at the end of our process to try to achieve the best result.