11.2 Design Review: DWG Compare, Traces & Shared Drawings

11.2 Design Review: DWG Compare, Traces & Shared Drawings

As architectural and engineering projects progress through schematic design, design development, and construction documentation, managing drawing revisions becomes increasingly complex. Design teams traditionally relied on manual visual checks, third-party PDF overlays, or physical redline prints to catch design discrepancies. AutoCAD replaces these error-prone manual practices with three deeply integrated collaboration and review features:

1. DWG Compare (DWGCOMPARE): An automated vector comparison engine that highlights geometric and property modifications between two revisions of a drawing.
2. Trace (TRACE): A digital "tracing paper" markup environment that permits internal and external team members to add annotations, sketches, and dimensions without modifying host drawing geometry.
3. Share Drawing (SHARE): Sends a link to a copy of the drawing that opens in the AutoCAD web app with view-only or edit permission.

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The DWG Compare Engine: Visual Revision Auditing

The DWGCOMPARE command evaluates the current active drawing against a selected comparison drawing file, automatically generating color-coded visual graphics and revision clouds around detected differences.

┌────────────────────────────┐      ┌────────────────────────────┐
│      Current Drawing       │      │     Compared Drawing       │
│         (File A)           │      │         (File B)           │
└──────────────┬─────────────┘      └──────────────┬─────────────┘
               │                                   │
               └─────────────────┬─────────────────┘
                                 │ DWGCOMPARE
                                 ▼
┌────────────────────────────────────────────────────────────────┐
│                    COMPARISON DISPLAY CANVAS                   │
│  🟢 GREEN:  Objects found ONLY in Current Drawing (File A)     │
│  🔴 RED:    Objects found ONLY in Compared Drawing (File B)    │
│  ⚪ GRAY:   Identical / Unchanged Objects in both files        │
│  ☁️ CLOUD:  Revision clouds enclose clusters of differences    │
└────────────────────────────────────────────────────────────────┘

Default Visual Color-Coding Hierarchy

When a comparison is initialized, AutoCAD locks the view into a temporary comparison state governed by a standardized color palette (customizable in the Settings panel):

• Green (only in the current drawing): Objects that exist only in the current drawing, such as elements added to the active file since the compared version.
• Red (only in the compared drawing): Objects that exist only in the comparison drawing, such as elements that were deleted from the active file or exist only in the other version.
• Gray (No differences): Objects that are identical in geometry and position between both drawings. Graying out identical objects reduces visual clutter and directs immediate attention to changes.

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The Comparison Toolbar and Difference Navigation

During an active comparison session, AutoCAD docks the DWG Compare Toolbar along the top of the drawing area. This toolbar contains essential inspection, filtering, and geometry exchange tools.

Navigation and Revision Cloud Settings

• Previous (<) and Next (>) Difference Buttons: Automatically zooms into and centers the viewport on each detected change cluster in sequence. This systematic stepping ensures drafters review 100% of revisions without overlooking subtle changes.
• Revision Clouds Toggle and Shape: Governs the visual clouds enclosing difference groups. Drafters can toggle cloud display on or off and switch between Rectangular clouds (fast, grid-like bounding boxes) or Polygonal clouds (tighter, contour-hugging boundaries).
• Cloud Margin: Adjusts the offset distance (buffer) between the detected geometric differences and the surrounding revision cloud perimeter.

Filter and Visibility Toggles

Clicking the Settings gear on the toolbar expands advanced filter controls:

• Current / Compared / Unchanged Toggles: Individual lightbulb icons allow drafters to isolate specific states (e.g., turning off Unchanged gray geometry to view only net revisions).
• Compare Text: When enabled, compares character strings, font styles, and positions of single-line and multiline text. When disabled, minor text notes do not trigger revision clouds.
• Compare Hatches: When enabled, evaluates changes in hatch patterns, boundaries, and angles. Disabling hatch comparison is useful when extensive decorative hatching obscures critical wall or piping modifications.

Geometry Transfer and Snapshot Generation

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The Trace Collaborative Markup Workspace

Introduced to bridge desktop and cloud drafting, the Trace feature (TRACE) provides a multiplatform collaborative markup environment. Traces function as virtual sheets of transparent tracing paper overlaid on top of the host drawing.

                    ┌──────────────────────────────────────┐
                    │          TRACE OVERLAY LAYER         │
                    │   • Markup sketch lines & clouds     │
                    │   • Leader annotations & text notes  │
                    │   • Reviewer feedback & dimensions   │
                    └──────────────────┬───────────────────┘
                                       │ Overlaid non-destructively
                                       ▼
                    ┌──────────────────────────────────────┐
                    │          HOST DRAWING CANVAS         │
                    │   • Production model & paper space   │
                    │   • Unaltered, protected geometry    │
                    └──────────────────────────────────────┘

Non-Destructive Collaboration

The fundamental advantage of Trace is non-destructive integrity. In traditional workflows, when reviewers add markup dimensions, text notes, or redlines directly into a DWG, they risk inadvertently altering production layers, modifying geometry, or leaving stray vectors that plot on final deliverables.

In contrast, objects created on a trace exist exclusively within that trace markup overlay:

• Trace objects do not populate the standard drawing layer structure.
• Whether object snaps can use trace geometry while you view a trace is controlled by TRACEOSNAP, so sketches can guide drafting without becoming drawing objects.
• Trace content is stored separately from the drawing's own objects, so accepting a markup means redrawing or copying it into the drawing deliberately.

The Trace Palette and Multiplatform Workflow

The Trace Palette (TRACEPALETTEOPEN) manages all trace instances stored inside the drawing database. Each trace record displays the author's Autodesk account username, timestamp of creation, and last modification date.

Traces support an integrated cross-platform lifecycle:

1. Creation (Web / Mobile / Desktop; AutoCAD 2022 desktop could only view traces): A project manager on a tablet at a job site opens the DWG via the AutoCAD Web or Mobile app, creates a new trace named Site_Inspection_Punchlist, and sketches revision clouds with text notes.
2. Review in Desktop: The office CAD technician opens the drawing in AutoCAD Desktop and opens the Trace palette. The new trace appears immediately.
3. Resolution: The drafter inspects the markup, updates the host drawing geometry to match instructions, and marks the trace as completed or deletes it.

Working Modes: Trace Edit, Trace View, Front and Back

When a trace is open on AutoCAD desktop, the Trace toolbar switches between two modes:

• Edit mode (TRACEEDIT): You contribute to the trace. New lines, text, and revision clouds go onto the trace, not into the drawing.
• View mode (TRACEVIEW): You edit the parent drawing while the trace stays visible as a guide, so MOVE, TRIM, or STRETCH act on the real geometry beneath the markup.

Display order is separate from the mode:

• TRACEFRONT: Shows the active trace at full saturation and dims the host drawing (the tracing-paper effect; its opacity is set by TRACEPAPERCTL).
• TRACEBACK: Shows the host drawing at full saturation and dims the trace geometry (fading set by TRACEFADECTL).

AutoCAD 2024 and later add COPYFROMTRACE, which copies selected trace objects into the drawing at the same location (run it while a trace is open with TRACEBACK on), and Import Markup (MARKUPIMPORT), which brings a marked-up PDF or image in as a new trace.

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Sharing Drawings: Share Drawing (SHARE)

Objective 5.1.a covers collaborating through shared drawing files. The current tool is Share Drawing (SHARE, on the Collaborate tab). It uploads a copy of the current drawing, including its external references and images, and gives you a link to that copy in the AutoCAD web app.

1. Save the drawing, then run SHARE (or click Share Drawing).
2. Choose the permission for people who open the link:
   • View only: recipients can look at the drawing but not change it.
   • Edit and save a copy: recipients can edit in AutoCAD on the web and save their own copy.
3. Copy the link and send it.

Key facts:

• The link points to a copy. Later edits to your DWG are not reflected, so share again after revisions.
• Autodesk states that the link expires seven days after it is created.
• Recipients work in the browser-based AutoCAD web app instead of a desktop installation.

Shared Views (Removed in AutoCAD 2027)

Earlier releases also offered Shared Views (SHAREDVIEWS), which published a non-editable visual representation of the drawing to Autodesk Viewer, where reviewers could measure and comment. Autodesk removed Shared Views starting with the 2027 releases of AutoCAD-based products. If an item describes it, remember the difference: a shared view was a view-only visual extract, while Share Drawing sends a link to an actual copy of the DWG.

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Collaborative Technology Selection Matrix

Selecting the appropriate review tool depends on the collaboration goal, team relationship, and required deliverable: