OpenNest/docs/superpowers/specs/2026-03-17-shape-library-design.md

Shape Library Design Spec

Overview

A parametric shape library for OpenNest that provides reusable, self-describing shape classes for generating Drawing objects. Each shape is its own class with typed parameters, inheriting from an abstract ShapeDefinition base class. Inspired by PEP's WINSHAPE library.

Location

• Project: OpenNest.Core
• Folder: Shapes/
• Namespace: OpenNest.Shapes

Architecture

Base Class — ShapeDefinition

Abstract base class that all shapes inherit from.

public abstract class ShapeDefinition
{
    public string Name { get; set; }
    public abstract Drawing GetDrawing();

    protected Drawing CreateDrawing(List<Entity> entities)
    {
        var pgm = ConvertGeometry.ToProgram(entities);
        return new Drawing(Name, pgm);
    }
}

• Name: The name assigned to the resulting Drawing.
• GetDrawing(): Each shape implements this to build its geometry and return a Drawing.
• CreateDrawing(): Shared helper that converts a list of geometry entities into a Drawing via ConvertGeometry.ToProgram().

Shape Classes

Tier 1 — Basics (extracted from MCP InputTools)

Class	Parameters	Description
RectangleShape	Width, Height	Axis-aligned rectangle from origin
CircleShape	Diameter	Circle centered at origin
LShape	Width, Height	L-shaped profile — full width bottom, half-width top-left
TShape	Width, Height	T-shaped profile — full-width top bar, centered stem

Tier 2 — Common CNC shapes

Class	Parameters	Description
RingShape	OuterDiameter, InnerDiameter	Annular ring (two concentric circles)
RightTriangleShape	Width, Height	Right triangle with the right angle at origin
IsoscelesTriangleShape	Base, Height	Isosceles triangle centered on base
TrapezoidShape	TopWidth, BottomWidth, Height	Trapezoid with bottom edge centered under top
OctagonShape	Width	Regular octagon fitting within the given width
RoundedRectangleShape	Width, Height, Radius	Rectangle with arc corners

File Structure

OpenNest.Core/
  Shapes/
    ShapeDefinition.cs
    CircleShape.cs
    RectangleShape.cs
    RingShape.cs
    RightTriangleShape.cs
    IsoscelesTriangleShape.cs
    TrapezoidShape.cs
    OctagonShape.cs
    RoundedRectangleShape.cs
    LShape.cs
    TShape.cs

Geometry Construction

Each shape builds a List<Entity> (using Line, Arc, Circle from OpenNest.Geometry) and passes it to the base CreateDrawing() helper. Shapes are constructed at the origin (0,0) with positive X/Y extents.

• Lines for straight edges
• Arcs for rounded corners (RoundedRectangleShape) and ring segments
• Circles for CircleShape and RingShape outer/inner boundaries

MCP Integration

InputTools.CreateDrawing in OpenNest.Mcp will be refactored to instantiate the appropriate ShapeDefinition subclass and call GetDrawing(), replacing the existing private CreateRectangle, CreateCircle, CreateLShape, CreateTShape methods.

Future Expansion

• Additional shapes (Tier 3): Single-D, Parallelogram, House, Stair, Rectangle with chamfer(s), Ring segment, Slot rectangle
• UI shape picker with per-shape parameter editors
• Shape discovery via reflection or static registry