WHAT ARE UVs?

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UVs are a 2D map of a 3D model’s surface. Just like you might flatten an orange peel to lay it out on a table, UV unwrapping takes a 3D object and lays its surface flat so textures know exactly where to go.

When a texture is applied, the software looks at the UVs to determine which part of the image appears on each part of the model. Without UVs, textures would stretch, smear, or appear in the wrong places. Good UVs ensure details line up correctly, edges stay clean, and patterns behave predictably.

A well-unwrapped model not only makes texturing easier but also improves performance. While alternative projection methods exist, they often sacrifice this performance and control, making UVs the industry standard. A skilled artist creates not only stunning art but also optimized assets. Think of unwrapping as a puzzle, one that becomes second nature with practice.

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KEY TERMINOLOGY

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UV SPACE

UV space is the literal box that your UV’s have to fit in when creating a unique texture for your model. The name comes from the axis that it’s using: because X, Y and Z were already taken, we use U and V instead! The letters U and V simply represent the horizontal and vertical directions on a flat map, similar to X and Y on a graph.

The axes in the 2D space are named U and V to differentiate them from X, Y, and Z (used in the 3D space)! It’s also where the name UV comes from!

We refer to this space as the “UV Space” or occasionally the “0 - 1 Space” or “Packing Box”. This space goes from 0 (origin) to 1 in both of the bidimensional axes.

It’s important to note that not all scenario’s require the textures to be limited within this space, some textures like Trimsheets or Tileable textures often require you to go outside of it.

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One thing to keep in mind is that UVs tile infinitely:

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This is important, as it creates two different methods for texturing: using unique (object specific) textures, or a method called “tileable” texturing (aka "trim texturing"). We’ll get into the differences of the two more deeply throughout this lesson, but first we’ll go over the principles that apply to both methods of texturing!

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UV ISLANDS

UV Islands are the individual pieces that make up the 2D representation of our 3D model. To create these islands, we need to cut seams where the model will "unfold," allowing us to flatten it with as little distortion as possible.

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SEAMS

Seams represent the cuts in our model that allow us to then unfold and flatten our islands. We create them by selecting edges/edge loops and marking them as seams within our modelling or unwrapping software.

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There are a several key rules to keep in mind regarding seams:

KEEP SEAMS TO A MINIMUM
‍Fewer seams mean fewer visible breaks in the texture, as well as fewer UV islands to pack. This reduces wasted space between islands (since each island requires edge padding). Minimizing seams also help performance: every UV seam results in vertices being calculated twice along that edge, increasing the engine's processing load.

HIDE YOUR SEAMS
‍Seams can create visible breaks in your textures, so it's best to place them in areas that won't be noticed. Try adding seams in less visible spots, like cavities or recessed areas, the bottom or back of your model, or parts of the mesh that are covered by other components. By strategically placing seams, you can avoid unwanted texture discontinuities and keep your model looking seamless and natural!

ALL HARD EDGES MUST HAVE SEAMS, THOUGH SEAMS DON’T REQUIRE HARD EDGES
‍When creating a model that will have a baked normal map, if you have a hard edge in your model, you always should add a seam to it. If no seam is present on your hard edges, your baked bevels will have visual errors. However, it’s important to note that just because you place a seam doesn’t mean you have to harden the edge! Seams work perfectly fine on smooth surfaces.

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Take a moment to examine this model and think about where seams would make sense:

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UNFOLDING

Unfolding is the process of a 3D software converting a 3D surface into a flat 2D layout while preserving the shape and proportions of the original surface as much as possible. Unfolding is, for the most part, automatic in most 3D software. Once seams have been properly set up, it will then try to do the best it can to unfold our 3D model in the 2D space based on the seams we’ve created. After unfolding, a model's UV islands typically have to be cleaned up, optimized, and packed (properly placed).

Depending on the shape of your model, different projection methods can help simplify the unwrapping process. Cylindrical, spherical, and cube projections work great for objects with matching forms, while planar projection, whether based on an axis or the camera view, is a solid choice for continuous surfaces.

It's also worth testing both Conformal and Angle-Based unwrap modes to see which works better for your model.

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Once seams are in place and the model unfolded, we’ll have our UV islands. Some will be good to go right away, but others might need some adjustments to make them as clean and efficient as possible. Iteration is important to get the best results.

Relax and adjust islands by minimize distortion or remove any overlaps. This can be achieved by manually grabbing and dragging portions of the UV mesh, or playing around with unwrap settings.

Straighten islands when possible, especially along the outer edges and seams. Since textures are made of square pixels, keeping UVs straight helps avoid issues like aliasing or jagged transitions, making the final result much cleaner!

Most modelling software comes with built-in tools to handle unfolding and unwrapping, but there are also plenty of add-ons that can make the process easier and deliver even better results. If you’re using Blender, it’s worth looking into UV add-ons. You may also consider looking into RizomUV, a powerful software tool designed specifically for UV unwrapping. One step at a time, though: let’s keep focusing on the fundamentals for now!

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CHECKER MAPS

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Checker maps are placeholder textures that will help you double check if there is any distortion or stretching in your UV map. Check if everything is properly aligned, ensure consistent scale across details, and see if any seams are too visible.

Most 3D software includes a built-in checker map in their unwrapping tools, but you can always find custom ones online. Add-ons like TexTools also come with handy checker maps that you can apply with a single click.

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ISLAND ORIENTATION

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Orientation of islands is important to minimize work later down the line and also to help with alignment to our pixel grid (remember that our textures used by our UV’s are a pixel representation). We’ve gone over why it’s important to align UV islands horizontally or vertically: to minimize artifacts caused by the square nature of pixels — but orienting the pieces correctly is just as vital!

The reason why orientation is handy, is when texturing we can align directional textures in one go. Take wood textures, for example — aligning all wooden pieces horizontally causes the pattern to naturally follow a consistent direction, making it look realistic. If your UVs aren’t aligned, you’ll be forced to create separate layers with different rotations for each piece, adding unnecessary work to an avoidable problem. Aligning similar pieces also helps keep texturing program file sizes down!

Some custom engine shaders also rely on UV direction, foe example rain effects that flow downward or dirt gradients that build up from the ground. To make these work correctly, always aim to orient your UVs to match how the object exists in the world space.

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TEXEL DENSITY

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Texel Density (TD) is all about how many pixels cover a certain area of your 3D model. It helps keep texture quality consistent across assets and determines the texture size needed to maintain that consistency.

Think about it like this: a 1024x1024 texture can look crisp on a small object like a screwdriver but it would be low-res for something massive like a helicopter, making the larger object look blurry and out of place. Understanding TD helps you plan your UV packing and texture sizes for the best results.

TD is measured in pixels per centimeter (px/cm) or pixels per meter (px/m), often shortened to “ppm.”

Texel Density isn’t the resolution of your textures itself, but it's affected by both texture size and the physical scale of your model.

But most of the time, we just need to be aware of what texel density we’re working towards, figure out the appropriate texture size and then let a tool like “Texel Density Checker” do the rest for us.

Here’s a more in-depth look at Texel Density.

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PACKING ISLANDS

Packing is the process of arranging UV islands within the UV space to make the most efficient use of the available texture area. After unwrapping a model, the UV islands are often scattered, rotated randomly, and leave a lot of empty space. Packing organizes these islands so they fit together as tightly as possible without overlapping.

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The way you pack your islands can change a bit depending your texturing methods! There are the two primary methods. Assets with Unique Textures and Assets with Tileable Textures. We’ll be focusing on how it’s done with unique assets first.

For individual props and items, all of your UVs must be packed inside of a 0-1 UV space (refer to the beginning of this lesson to recap this concept). It is possible to have overlapping and mirrored islands that you will usually move outside the space when baking, but you will need to put them back inside the box for final export/import in engine.

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PADDING AND DILATION

After learning how to lay out your UV islands, the next step is making sure they’re properly spaced. This is where padding and dilation come in!

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What is Padding?

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In this image you can see how there is enough pixel space (padding) between islands. If they were closer together we would probably run into issues. You need to find the balance between maximizing the used space for a higher TD, and having enough space between islands.

Padding is just the amount of space (in pixels) between UV islands and the edges of your UV layout. It might look like wasted space, but it’s actually crucial to avoid texture bleeding. You can space things out manually, but if you want to be precise and optimize your UV packing, it’s recommended to use tools or add-ons to calculate padding. Maya has built in features for this, and Blender has add-on options such as UV PackMaster that lets you set exact pixel spacing between islands and the UV borders. It’s a paid add-on, but worth every cent. If you’re on a budget, there are free alternatives out there too. Do a bit of research to find what works best for you!

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How much padding should you use?‍

It depends on your engine and pipeline, but here’s a solid starting point based on texture size:

• 2048x2048 → 16px padding
• 1024x1024 → 8px padding
• 512x512 → 4px padding

For the margin between your UV islands and the edge of the packing box, you can either keep the same spacing as between the islands or, if you want to optimize texture space as much as possible, use half that amount. For example, if there is 16 px of padding between islands, you can use 8 px between the islands and the edge of the packing box. This works because the 0–1 UV space tiles indefinitely, meaning the padding from opposite sides of the UV border combines, effectively providing the full 16 px of spacing.

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What is Dilation?

Dilation is the process of filling in the empty space around the edges of your UV islands with color to prevent visible seams and texture bleeding! This is especially useful when mipmaps or lower-resolution versions of a texture are generated by an engine. Instead of leaving that space blank, dilation fills it with relevant texture data for smoother rendering.

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When exporting textures in Substance Painter, Designer, and other similar tools, you can select how much dilation (in pixels) you’d like the program to create. If you’ve already left enough padding between your UV islands, dilation won’t cause any issues. In fact, you can even use infinite dilation, which stretches the texture from each island all the way into the mid-point between two islands, like in the above image.

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OVERLAPPING UVs

UV overlapping is the process of stacking UV islands directly on top of one another, allowing them to share the same texture space and maximize texture efficiency. It is a common practice, and most models contain areas where overlapping UVs can be used effectively. Since these islands will display identical texture details, it's important to be mindful of repetition, as excessive reuse can make an asset look unnatural. The key is finding the right balance between optimization and visual variety.

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When SHOULD you overlap UVs?

• ‍Repeating or reused parts are ideal candidates for overlapping UVs. Small, identical elements, such as screws, bolts, vents, or buttons, can be unwrapped once and duplicated. By overlapping their UVs, you texture a single element while all duplicates share the same texture, saving valuable UV space.
• The smaller and more generic the element, the better overlapping works. Repetition on simple shapes is rarely noticeable, especially compared to larger or more distinctive parts of a model.
• ‍Symmetrical or mirrored elements work well with overlapping UVs. Since these parts usually sit on opposite sides of a model, mirrored textures are much harder to notice. For example, when modelling a fridge, you can UV one side and mirror the other, while keeping the front and back unique. This approach preserves visual quality where it matters most while significantly optimizing UV space.
• ‍Non-visible or rarely seen faces are also good candidates for overlapping UVs. If certain parts of the model are unlikely to be seen in-game, such as the bottom of an object or interior faces, you can overlap their UVs with other areas to avoid wasting texture space, as long as it doesn’t create shading or baking issues.
• Overlapping non-visible faces works really well when you have parts of your model that aren’t likely to be seen, but you still want to keep the geometry for a cleaner model and to avoid potential errors. You don’t need the geometry to match perfectly to overlap UVs — though it helps if the shapes are somewhat similar. Going back to the fridge example: if you know the bottom face won’t be visible in-game, you can overlap its UV island with one of the side islands. This gives you extra texture info without wasting any space.

Remember, when overlapping UVs, you always need to offset the overlapping UV’s by at least 1 UV space.

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When should you not overlap UVs?

• ‍Unique or prominent details should not overlap. Any key features that draw attention such as logos, decals, text, serial numbers, or highly detailed parts of the mesh, need their own UV space. Overlapping these areas will cause visible repetition or mirroring, which quickly breaks realism.
• ‍Larger or hero props should be handled carefully when it comes to overlapping UVs. The larger and more important an asset is, the more noticeable texture repetition becomes. Overlapping UVs can make texturing harder and reduce visual quality, so these assets usually need more dedicated UV space to maintain consistency and clarity.
• ‍Areas with unique wear and tear are poor candidates for overlapping. Real-world wear is rarely symmetrical—scratches, chipped edges, dirt buildup, and rust patterns are all irregular. Overlapping UVs will force these details to repeat in unnatural ways.
• ‍Faces that are likely to be seen at the same time should not share UV space. For example, surfaces that face each other or are visible simultaneously in-game, such as the front and back of a character or the inside and outside of an object, can create obvious texture repetition or visual mismatches if overlapped.
• ‍Textured assets that rely on baked maps (such as normal maps, ambient occlusion, or curvature) generally require unique UVs. Overlapping can cause baking artifacts, lighting errors, or incorrect shading, since multiple surfaces are trying to use the same texture information.

As a rule of thumb: if the surface is important, highly visible, or needs unique detail, it deserves unique UV space. Overlap UVs only where repetition won’t be noticed and won’t interfere with the final visual quality.

UVs FOR TILEABLE TEXTURING

The second method relates to Tileable Texturing. Tileable texturing is where, instead of only using a 0-1 texture space, a texture repeats (”tiles”) seamlessly over a surface without any visible edges or breaks. This is often used for things like floors, walls, fabrics, or anything that needs to cover a big area without stretching a single texture too much.

Instead of unwrapping and packing an object in a 0-1 space, and uniquely texturing, say the above tower, you may unwrap it and apply a tileable texture that loops infinitely, only scaling up or down the UV to adjust the Texel Density (modifying how big or small the tiling pattern will be).

This saves UV space and texture memory. It's a great way to keep textures looking sharp while optimizing performance, especially in games where unique textures for everything would be waaay too heavy. The main priority with Tileable Textures is keeping their Texel Density exactly at the target value. If you need a specific detail to show up in a certain area, you can adjust your UV islands to match that detail.

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Trim Sheets

This is where Trim Sheets come in! Trim sheets are a super efficient way to texture assets, especially for games and large environments. Instead of giving each model its own unique UV layout and texture, a trim sheet is a single, seamless texture that multiple assets can share by aligning their UVs to specific sections of the sheet.

Imagine a texture with different types of trims, panels, and surface details laid out in strips. You map different parts of your model to these strips, letting you reuse the same texture across multiple objects while keeping them looking detailed and high-res. This method is great for things like walls, pipes, railings, and architectural details, where you don’t need unique texturing for every single piece.

Since trim sheets don’t follow the usual 0-1 UV space rules, you can tile them as needed, scaling and repeating sections to match the asset’s dimensions. They’re a game-changer for optimization, cutting down on texture memory usage while keeping visual quality high.

If you’re making modular pieces that need to tile seamlessly, you’ll have to make sure the end of one UV island lines up perfectly with the start of the next. This is usually done by snapping them to the grid or aligning them with the boundaries of the 0-1 space, depending on your target Texel Density and scale requirements.

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A tileable texture is like wallpaper that repeats endlessly, while a trim sheet is like a toolbox of reusable strips you cut from and place onto different parts of a model. Combining the two is a powerful approach to optimization.

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SOFTWARE OPTIONS FOR UV UNWRAPPING

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TROUBLESHOOTING COMMON ERRORS

Incorrectly made UVs can cause a couple issues. Here are some typical issues to watch out for!‍

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Jagged Edges along Seams

When you see thin jagged artifacts along the hard edges of your model, it is because you haven’t placed seams on those hard edges, or there isn’t enough padding between the islands. The reason for this is that the baker is trying to calculate the normal values of your bevel from both angles, leading to some pinching in the normal map along those hard edges. The fix for this is to simply include seams along all hard edges, and give the UV islands enough padding, resulting in a smoother transition between the UV islands.

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Baking Errors

Having overlapping UVs in a 0-1 space will mess with with baking. This will cause errors in the bakes and affect texture application. The fix is simple: move your overlapping islands outside the packing box before baking, do your bakes, and once done, you can move them back to their original position (just make sure to offset them properly to avoid any issues). It’s a quick workflow to avoid those errors and keep everything clean.

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Noticeable Repetition

Noticeable repetition in UVs and texturing refers to visible patterns or repeated texture details that stand out unnaturally across a surface, making it obvious that the same texture has been reused. You don’t want objects with overlapping UVs that are too large, too important, easy to identify, or placed very close to each other. You need to be intentional about what you choose to overlap and do as much as possible to hide that repetition. Applying different transforms to objects with overlapping UVs can also help solve this problem. A different rotation or a small size variation can go a long way in breaking up that perfect repetition.

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The Butterfly Effect

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The "Butterfly Effect" is something to watch out for when mirroring a face with a symmetry modifier, especially when the mirror line runs directly down the center of the object. While mirroring is great for saving time, any detail placed on that center line will be duplicated on both sides, creating a symmetry duplication effect. It might work in some cases, but it can also lead to obvious symmetrical repetition that stands out.

To avoid this, place key details slightly off-center before mirroring, or plan to introduce subtle asymmetry afterward by manually adjusting one side. You can also add variation through layered texturing. Using decals, vertex painting, or procedural textures can help break up symmetry and give each side unique details, helping to disguise mirrored geometry.

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CONCLUSION

UV unwrapping can feel intimidating at first, but like any skill, it becomes easier and more intuitive with practice. Every model you unwrap builds your problem-solving instincts and your understanding of how textures interact with form. Don’t aim for perfection on your first pass: aim for clarity, cleanliness, and intent. During the early baking and texturing stages (the next steps!) of the modeling process, artists often continue refining their UVs to make sure everything is visually correct.

Remember that strong UVs are doing a lot of the heavy lifting behind the scenes. They give you control, consistency, and the freedom to focus on creativity instead of fixing errors. Treat unwrapping as part of the artistic process, not just a technical step, and you’ll see your future textures improve faster than you expect.

Now it’s time to put your UV knowledge to work. Follow along with our exercises for Unwrapping, or jump right into the next step of the modelling process: baking!

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