> ## Documentation Index > Fetch the complete documentation index at: https://docs.opengeometry.io/llms.txt > Use this file to discover all available pages before exploring further. # Arc > A circular arc primitive defined by center, radius, and angles ## Overview The Arc primitive represents a segment of a circle in 3D space. It is defined by a center point, radius, start angle, end angle, and the number of segments used for tessellation. When the angle range equals 2π, the arc forms a complete circle. **Use Cases:** * Creating circular arcs and curves * Drawing complete circles * Rounded corners and fillets * Circular patterns and designs ## Constructor ```rust theme={null} let arc = OGArc::new("arc-1".to_string()); ``` ```typescript theme={null} const arc = new Arc(options?: IArcOptions); ``` ### Rust Constructor Parameters Unique identifier for the arc instance ### TypeScript Constructor Parameters Configuration options for the arc Optional unique identifier (auto-generated if not provided) Center point of the arc Radius of the arc Starting angle in radians Ending angle in radians Number of line segments to approximate the arc (higher = smoother) Arc color as a hexadecimal number (e.g., 0x00ff00 for green) Enable thick line rendering using Line2 Line width when fatLines is enabled ## Methods ### set\_config ```rust theme={null} arc.set_config( center: Vector3, radius: f64, start_angle: f64, end_angle: f64, segments: u32 ); ``` Updates the arc's geometric parameters. ```typescript theme={null} arc.setConfig(options: IArcOptions); ``` Updates the arc configuration and regenerates geometry. ### generate\_geometry ```rust theme={null} arc.generate_geometry(); ``` ```typescript theme={null} // Called automatically by setConfig ``` Generates vertices along the arc using the specified number of segments. For closed arcs (full circles), it automatically creates a face. ### get\_geometry\_serialized ```rust theme={null} let geometry: String = arc.get_geometry_serialized(); ``` ```typescript theme={null} // Used internally for rendering ``` Returns serialized vertex buffer data as a JSON string. ### get\_brep\_serialized ```rust theme={null} let brep: String = arc.get_brep_serialized(); ``` ```typescript theme={null} const brep = arc.getBrep(); ``` Returns the complete BREP representation including vertices, edges, and faces. ### getConfig ```typescript theme={null} const config = arc.getConfig(); ``` Returns the current arc configuration. ### discardGeometry ```typescript theme={null} arc.discardGeometry(); ``` Disposes of the current geometry (called automatically before regeneration). ## Properties Unique identifier for the arc instance Center point of the arc (default: origin) Radius of the arc (default: 1.0) Starting angle in radians (default: 0.0) Ending angle in radians (default: 2π) Number of segments for tessellation (default: 32) Internal BREP representation containing vertices, edges, and optionally a face for closed arcs Arc color (TypeScript only, settable) ## Code Examples ### Creating a Semicircle ```rust theme={null} use opengeometry::primitives::OGArc; use openmaths::Vector3; use std::f64::consts::PI; let mut arc = OGArc::new("arc-1".to_string()); arc.set_config( Vector3::new(0.0, 0.0, 0.0), // center 5.0, // radius 0.0, // start angle PI, // end angle (180 degrees) 32 // segments ); arc.generate_geometry(); ``` ```typescript theme={null} import { Arc, Vector3 } from "opengeometry"; const semicircle = new Arc({ center: new Vector3(0, 0, 0), radius: 5, startAngle: 0, endAngle: Math.PI, segments: 32, color: 0x00ff00 }); ``` ### Creating a Full Circle ```rust theme={null} use std::f64::consts::PI; let mut circle = OGArc::new("circle-1".to_string()); circle.set_config( Vector3::new(0.0, 0.0, 0.0), 3.5, 0.0, 2.0 * PI, // Full circle 64 // Higher segments for smoother circle ); circle.generate_geometry(); ``` ```typescript theme={null} const circle = new Arc({ center: new Vector3(0, 0, 0), radius: 3.5, startAngle: 0, endAngle: Math.PI * 2, segments: 64, color: 0xff0000 }); ``` ### Creating a Quarter Arc ```typescript theme={null} const quarterArc = new Arc({ center: new Vector3(5, 0, 5), radius: 2.0, startAngle: 0, endAngle: Math.PI / 2, // 90 degrees segments: 16, color: 0x0000ff }); ``` ### Using Fat Lines for Arcs ```typescript theme={null} const thickArc = new Arc({ center: new Vector3(0, 0, 0), radius: 10, startAngle: 0, endAngle: Math.PI * 1.5, segments: 48, color: 0xff00ff, fatLines: true, width: 30 }); ``` ### Updating Arc Parameters ```typescript theme={null} arc.setConfig({ center: new Vector3(0, 0, 0), radius: 7.5, startAngle: Math.PI / 4, endAngle: Math.PI * 1.75, segments: 40, color: 0xffff00 }); // Change color arc.color = 0x00ffff; ``` ## Live Demo Try the Arc primitive in the browser ## See Also Smooth curves through control points Straight line segments Connected line segments