Scopes

Overview

The .duc format features a logarithmic Infinite Zoom and Unit Scope engine capable of spanning 64 orders of magnitude (10⁻³² to 10³²).

Instead of hardcoding a fixed unit for a canvas, .duc manages document geometry through unit scopes (mm, µm, nm, m, km, in, ft, mi), dynamically determining the active unit scale based on zoom depth and document settings.

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Core Scope Concepts

1. Base Reference Unit (NEUTRAL_SCOPE)

All raw spatial data (element positions, stroke widths, bounding boxes, vector paths) are normalized relative to the meter (NEUTRAL_SCOPE = "m"). This guarantees zero coordinate distortion when rendering the same file across different CAD applications or unit systems.

2. Main Scope (main_scope)

The designated master unit of the document (e.g. mm for mechanical components, m for architectural site plans, mi for civil infrastructure). Stored in duc_global_state:

• main_scope: The primary measure (e.g., mm, in, m).
• scope_exponent_threshold: Defines the gravity well threshold for unit transitions.

3. Main Scope Gravity Well

To prevent rapid, jarring unit transitions when zooming near a project’s primary unit scale, .duc implements a gravity well effect.

When the current zoom exponent is within the scope_exponent_threshold from main_scope, the engine locks the active display unit to main_scope. Beyond this threshold, it smoothly falls back to natural logarithmic unit selection.

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Supported Measurement Definitions

.duc supports both Metric and Imperial measurement unit definitions:

Metric Units (Powers of 10)

Imperial Units (Meter Equivalents)

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Dynamic Unit Scaling

For details on how .duc preserves lossless geometric precision across different scopes without modifying an element’s original measure, see the Infinite Precision & Scoped Values page.