> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/templates/cadd.md).

# CADD

This section describes the CAD primitives used to draft 2D drawings inside an OpenBrIM project — plan views, elevations, cross sections, deck plans, foundation plans, details, and the dimensions and annotations that go on top of them. Each primitive has its own page covering what it's for, the parameters that control it, and how to edit it in the CAD viewer.

The "i" button in the property panel for each shape opens its page directly. The same pages are linked from the FEA / CAD trees in the spreadsheet view.

## Document and layers

* [CAD Document](/templates/cadd/cadd-document.md) — the top-level container for a 2D drawing (a sheet's worth of geometry).
* [Level (CAD Layer)](/templates/cadd/level-cadd.md) — the layer system that controls per-shape color, line weight, and dash style.

## Geometric primitives

* [Line](/templates/cadd/line-cadd.md) — open polyline of two or more points; for centerlines, leaders, breaklines, working lines.
* [Circle](/templates/cadd/circle-cadd.md) — circle by center and radius; for piles, dowels, anchor bolts, drilled-shaft outlines.
* [Rectangle](/templates/cadd/rect-cadd.md) — rectangle by center, width, and height; for pier outlines, footings, plates, panels.
* [Arc](/templates/cadd/arc-cadd.md) — arc of a circle; for fillets, return arcs, curved abutment outlines.
* [Ellipse](/templates/cadd/ellipse-cadd.md) — ellipse by two radii; for elliptical foundations and aesthetic curves.
* [Bezier Curve](/templates/cadd/bezier-cadd.md) — smooth curve shaped by control points; for transitions and aesthetic boundaries.
* [Curve](/templates/cadd/curve-cadd.md) — smooth curve passing through every control point; for surveyed traces and splines.
* [Container](/templates/cadd/container-cadd.md) — group of shapes that move, rotate, and style together.

## Background and 3D-derived

* [Background Image](/templates/cadd/backgroundimage-cadd.md) — raster or PDF reference underlay for tracing.
* [CADD From 3D](/templates/cadd/caddfrom3d-cadd.md) — auto-generated 2D projection from a specific 3D object.
* [CADD From Section](/templates/cadd/caddfromsection-cadd.md) — auto-generated 2D section view driven by an alignment (cross sections, profile elevations, deck plans).

## Dimensions

* [Linear / Aligned Dimension](/templates/cadd/dimensionline-cadd.md) — distance between two points (horizontal, vertical, or aligned).
* [Angular Dimension](/templates/cadd/dimensionangular-cadd.md) — angle between two lines (skew angles, turning angles).
* [Radius Dimension](/templates/cadd/dimensionradius-cadd.md) — radius of an arc or circle.
* [Diameter Dimension](/templates/cadd/dimensiondiameter-cadd.md) — diameter of a circle (piles, drilled shafts, anchors).
* [Arc Length Dimension](/templates/cadd/dimensionarclength-cadd.md) — length along a curved edge.
* [Elevation Dimension](/templates/cadd/dimensionelevation-cadd.md) — elevation above datum (top of pier, top of deck, etc.).
* [Ordinate Dimension](/templates/cadd/dimensionordinate-cadd.md) — coordinates of a point relative to an origin.
* [Slope Dimension](/templates/cadd/dimensionslope-cadd.md) — grade between two points (percent, ratio, or rise per run).

## Annotations

* [Station Offset](/templates/cadd/stationoffset-cadd.md) — alignment-relative point callout (Station + Offset).
* [Text](/templates/cadd/text-cadd.md) — free-form text block.
* [Leader Note](/templates/cadd/note-cadd.md) — text with a leader arrow pointing at a feature.
* [Pin](/templates/cadd/pin-cadd.md) — fixed-size symbol marker for highlighting a point.
* [Revision Cloud](/templates/cadd/cloud-cadd.md) — scalloped boundary marking a revised region.
* [Section Callout](/templates/cadd/sectioncallout-cadd.md) — section reference bubble (`A` / `A`, `B` / `B`).

## Common concepts

**Levels (layers).** Every shape belongs to a Level, which controls color, line weight, and dash style. Routing styling through Levels rather than per-shape is what gives bridge drawings their conventional look — heavy black for cut concrete, light gray for working lines, dashed for hidden, red for revisions.

**Alignment-driven drawings.** When the parent CAD Document is bound to an alignment, shapes drawn in flat coordinates are automatically bent to follow the bridge geometry — straight lines become curved over horizontal curves, rectangles become trapezoidal in plan, etc. Useful for working lines, footprints, and overlays that should track the alignment without being redrawn on every revision.

**Drawings that update with the model.** Section views (CADD From Section), 3D-derived views (CADD From 3D), and dimensions all rebuild automatically when the underlying 3D model or alignment changes. You author the drawing once and the geometry stays correct across revisions.


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