What Does Pack Islands Do in Blender?

The Pack Islands command in Blender is an essential UV unwrapping tool that automatically arranges, scales, and fits individual 2D texture coordinates (known as UV islands) within the standard 0-to-1 UV grid space. This feature optimizes your texture space by reducing wasted area, preventing overlapping geometry, and ensuring efficient texture usage across your 3D models.

How Pack Islands Works

When you unwrap a 3D object, Blender splits the mesh along designated seams into flat 2D pieces called UV islands. Managing these pieces manually can be time-consuming.

Running the Pack Islands command (accessible in the UV Editor via UV > Pack Islands or by pressing Ctrl + P) makes Blender calculate the shapes of all selected islands and automatically position them tightly together, minimizing empty space while keeping individual pieces distinct.

Key Options and Settings

When you execute the Pack Islands command, an operator panel appears in the bottom-left corner of the UV Editor. Adjusting these settings lets you control exactly how Blender packs your UVs:

  • Margin: Adds empty space (padding) between UV islands. Increasing the margin prevents texture "bleeding," where pixels from one island bleed into an adjacent island during rendering or mipmapping.
  • Rotate: Allows Blender to rotate islands during the packing process to find a tighter, more efficient fit.
  • Scale: Automatically resizes islands to fit within the UV boundary. You can choose whether Blender normalizes island scales relative to each other.
  • Shape Method: Determines how Blender calculates the bounds of each island:
    • Exact Shape: Analyzes the exact polygon outlines for the tightest possible packing.
    • Bounding Box: Treats each island like a rectangle, resulting in faster but less space-efficient packing.
    • Convex Hull: Groups the outer points of each island into a smooth outer boundary to speed up calculation time.
  • Lock Pinned Islands: Keeps pinned UV islands in their exact current position while non-pinned islands are packed around them.

Common Use Cases

  • Optimizing Texel Density: Ensures texture resolution is distributed evenly and efficiently across the entire 3D model.
  • Preparing Game Assets: Game engines rely heavily on efficient UV layouts to conserve memory and maintain performance.
  • Texture Baking: Prevents artifacts and overlapping errors when baking high-poly details, ambient occlusion, or normal maps onto low-poly geometry.