Using UDIMs in Blender: A UV and Texture Guide for Architectural Models

Which Blender version is this guide for?

This guide is based on the UDIM and Image Texture descriptions in the “latest” documentation provided by the Blender Manual. Since the documentation does not specify a particular Blender version, the steps cannot be tied to a specific release. It’s worth comparing the interface and features in your version of Blender with the relevant manual.

UDIM is a method for distributing a model’s UV islands across multiple texture tiles instead of squeezing them into a single image. When you use just one image, all areas of the model share the same resolution budget. A large or visually important surface may not get enough detail, while pixels allocated to smaller, less important areas may go to waste. UDIMs help balance this by assigning images at different resolutions to different areas.

Plan UDIM tiles and resolutions

1. Start with a regular UV workflow. Unwrap the mesh as you would when preparing a single UV map. UDIM doesn’t replace UV unwrapping; it lets you distribute the unwrapped UV islands across multiple image areas.

2. Decide how many textures to use. The number depends on the model and your workflow. Blender’s manual suggests starting with at least three images: a 4K texture for areas with important details, a 2K texture for less important areas, and a 1K texture. These resolutions are examples from the manual, not a fixed rule for every model.

3. Create the required tiles. The Sidebar › Image › UDIM Tiles panel in the UV Editor or Image Editor is used to manage UDIM tiles. You can add or remove tiles from the panel, or fill a tile with an image. When adding tiles, you can specify the starting number and how many tiles to add. A UDIM sequence must start at 1001.

4. Place UV islands on the target tiles. 1001 is the main tile; 1002 is to its right. The first row contains ten tiles, from 1001 to 1010. The next row continues above the main tile; for example, 1011 is above 1001. Keep this layout in mind and allocate more texture space to important surfaces.

Fill the images and manage files

1. Assign an image to each tile. Once you’ve created the tiles, prepare the appropriate images. According to Blender’s manual, an existing texture file cannot be added directly to a tile. To use an existing texture, first create the tiles and save the image; then change the contents of the saved file in another application, or delete the file and place a texture file with the same name in its place. UDIM textures can also be painted using 2D Painting or 3D Painting.

2. Make sure the tiles are saved. An empty tile is not saved with the image. If a tile contains data and is removed before being saved, that data may be lost. Check the tile list and confirm that the images have been saved to reduce the risk of missing textures.

3. Use substitution tokens in file names. Blender can replace the <UDIM> token in a file name with the tile number to associate each texture file. For example, a file named monster-basecolor.<UDIM>.png corresponds to a file name such as monster-basecolor.1021.png for tile 1021. The <UVTILE> token uses a naming format such as u1_v3. These tokens help identify tiles when loading or saving images.

Choose an Image Texture projection

1. Start with Flat projection if you’re using UVs. The Vector input on the Image Texture node can be connected to a coordinate source; if nothing is connected, the active UV map is used. Flat projection places the image on a unit square and works with UV maps, making it a natural choice when using manually unwrapped UV islands.

2. Consider Box for box-shaped architectural objects. Box projection places the image on the faces of a unit cube and projects according to surface normals. Blender’s documentation specifically notes its common use in architectural models containing many box-shaped objects. The Blend value mixes the results of multiple surfaces to smooth transitions from one face to another; higher values increase the blending and softness.

3. Choose interpolation to suit the surface and image. Linear offers standard quality; Cubic provides smoother, higher-quality scaling. The manual recommends Cubic for the best results with bump maps. Closest does not interpolate and is suitable for pixel art. Smart is described only for Cycles and Open Shading Language; it uses Cubic when scaling up and Linear when scaling down.

Common mistakes

• Leaving all UVs on a single tile: The purpose of UDIMs is to spread islands across multiple texture areas. Plan the number of tiles and identify which surfaces need more resolution from the start.

• Assuming empty tiles will be saved: Unfilled tiles are not saved with the image. Before delivery, confirm that every tile is filled and its files are present.

• Not choosing projection based on the object’s shape: Flat works with UV maps; Box is an option for box-shaped objects in architectural models. A projection that doesn’t suit your needs may produce unexpected texture placement.

• Overlooking interpolation for bump maps: The manual recommends Cubic interpolation for bump maps. Consider this option when checking how the texture looks.

Impact on architectural and visualization workflows

UDIMs can be useful when a single UV map’s resolution isn’t enough for surfaces with different levels of importance. For example, you can assign higher-resolution textures to visually prominent areas and lower-resolution images to less important ones. Box projection is also worth considering for box-shaped architectural objects, while Flat is the option cited in the manual for projects using UV islands.

Before starting your workflow, decide how many tiles you need, which images you’ll use, and how the files will be named. When using existing textures in particular, account for the file-replacement method described in Blender’s documentation and the warning about data loss in unsaved tiles. Since the documentation doesn’t provide hardware requirements or licensing terms, this guide makes no recommendations about them.