What is union in Inkscape?

In Inkscape, Union is a fundamental path operation used to combine the areas of two or more selected vector objects into a single, cohesive path.

Understanding Union in Inkscape

Union is one of Inkscape's powerful "path operations" accessible via the Path menu. Its core function is to merge overlapping or touching vector shapes into a single, unified object, simplifying complex designs and enabling the creation of new forms.

How Union Works

As a path operation, Union works on the areas defined by closed paths. The process can be described as follows:

• Area Combination: "Like most of the path operations, it works on areas. It takes the area inside one closed path and the area inside another closed path and puts them together, resulting in one closed path." This means that Inkscape essentially treats the objects as filled regions and combines their occupied spaces.
• Resulting Path: "Union typically results in one closed path, although not always." While the primary goal is to produce a single, merged shape, in certain complex scenarios involving disconnected or intricate original paths, the resulting "single path" object might still contain multiple sub-paths if the original components were not truly contiguous. The new path will inherit the fill and stroke attributes of the bottom-most object in the selection.

Practical Applications and Examples

Inkscape's Union operation is an indispensable tool for graphic designers, illustrators, and anyone working with vector graphics. It streamlines workflows and enables precise shape manipulation.

Accessing the Union Command

To perform a Union operation in Inkscape:

1. Select Objects: Select two or more path objects that you wish to combine.
2. Navigate to Path Menu: Go to the Path menu in the top toolbar.
3. Choose Union: Click on Union (or use the keyboard shortcut: Ctrl++ or Ctrl+Shift++ on some layouts).

Common Use Cases

• Creating Complex Shapes:
  • Combine multiple simple shapes (e.g., circles, squares) to form intricate designs like clouds, gears, or abstract symbols. For instance, merging several overlapping circles can easily form a cloud shape.
  • Build unique logo elements by fusing basic geometric primitives.
• Simplifying Artwork:
  • Reduce the number of individual objects in your design by merging elements that should act as one. This can make files smaller and editing more manageable.
  • Optimise paths by consolidating overlapping segments, leading to cleaner outlines, especially useful for cutting machines or CNC routing.
• Manipulating Text:
  • After converting text objects into paths (Path > Object to Path), you can use Union to merge individual letterforms into a single, continuous path. This is crucial for vinyl cutting, laser engraving, or creating custom typography where individual letters need to be treated as one shape.

Union vs. Group: What's the Difference?

While both Union and Group involve combining objects, their functionality and outcomes are fundamentally different.

Union is a destructive operation in the sense that the original paths are consumed to create a new one. It's often a good practice to duplicate objects (Ctrl+D) before applying Union if you think you might need the original shapes later.