> 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/circle-cadd.md).

# Circle

A **Circle** is defined by a center point and a radius. In bridge drawings you'll use it for piles in foundation plans, dowels and anchor bolts in details, drilled-shaft centerlines, hole layouts, plan-view circular columns, and any feature that's truly circular rather than a polygonal approximation.

To draw: click once to place the center, then click again to set the radius. The radius is the distance between the two click points. A dashed preview line during drawing shows the current radius.

## Geometry

**Name:** Identifier within the parent CAD document. Must be unique.

**Level:** The layer controlling color, line weight, and dash style. Common assignments: "Piles" for foundation plans, "Hardware" for dowel and anchor bolt symbols.

**Center X:** Horizontal coordinate of the circle's center.

**Center Y:** Vertical coordinate of the circle's center.

**Radius:** Distance from the center to the circle. Must be positive.

**Diameter (readonly):** Twice the radius. Shown for convenience when dimensioning by diameter.

**Circumference (readonly):** Length around the circle. Useful for rebar length take-offs on circular columns.

**Area (readonly):** Plan area enclosed.

## Editing

**Move the center:** drag the center handle to translate the circle.

**Resize:** drag any of the four quadrant handles (top, bottom, left, right) to change the radius. The center stays fixed; the radius updates symmetrically.

**Snap:** other shapes can snap to the center and to the four quadrant points (cardinal points on the circle).

**Offset:** create a concentric copy at a fixed distance — useful for showing pile-cap clearances around piles.

## Notes

When the parent CAD document is driven by an alignment, the circle's center is bent onto the alignment, but the circle stays a circle (it does not warp into an ellipse over a horizontal curve). This is the right behavior for piles and anchor bolts — they should remain round in plan even when the bridge is curved.

If you need a circular shape that does warp with the alignment (e.g., a circular hatch pattern that follows the bridge curvature), use a Container with a closed polyline approximating the circle.


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