ShapeDrawer

Abstract generic base class for all shape drawers in the ShapesDrawer system. Defines the queue-and-draw pattern: subclasses enqueue shape structs via an Add(...) method, and the system calls Draw() once per camera per frame to render the entire queue using the Shapes library. Also defines the IShapeDrawer interface used for type-erased access.

Definition

Namespace: Paragon.Core.ShapesDrawer Assembly: Paragon.dll

public interface IShapeDrawer
{
    Type Type { get; }
    void Draw();
    void Reset();
}

public abstract class ShapeDrawer<TShape> : IShapeDrawer
    where TShape : struct

Implements: IShapeDrawer

Remarks

ShapeDrawer<TShape> provides the shared infrastructure for all shape types:

• A List<TShape> draw queue that collects shapes throughout the frame.

• Default Shapes library style settings (LineGeometry.Volumetric3D, ThicknessSpace.Pixels).

• A Reset() method called each frame at PRE_UPDATE to clear the queue.

• An abstract Draw() method that subclasses override to iterate the queue and issue Shapes library draw calls.

The IShapeDrawer interface provides non-generic access for the ShapesDrawer singleton, which stores all drawers in a Dictionary<Type, IShapeDrawer>.

Quick Lookup

Goal	How
Create a new shape drawer	Subclass ShapeDrawer<TShape>, define a nested struct, override Draw()
Enqueue a shape	Add to drawQueue (typically via an Add(...) method)
Render all shapes	Override Draw() — called automatically by ShapesDrawer
Clear the queue	Reset() — called automatically each frame

Properties

Type

The concrete runtime type of this drawer. Used as the dictionary key in ShapesDrawer.

public Type Type { get; }

Fields

drawQueue

The queue of shapes to render this frame. Subclasses add to this in their Add(...) method.

protected readonly List<TShape> drawQueue;

lineGeometry

Default line geometry mode for line-based shapes.

protected LineGeometry lineGeometry = LineGeometry.Volumetric3D;

thicknessSpace

Default thickness space for shape rendering.

protected ThicknessSpace thicknessSpace = ThicknessSpace.Pixels;

Methods

Draw

Renders all shapes in the drawQueue. Subclasses must override this to iterate the queue and issue Shapes library draw calls within a PushStyle() / PopStyle() block.

public abstract void Draw();

Reset

Clears the draw queue. Called automatically at PRE_UPDATE by ShapesDrawer. Can be overridden for additional cleanup.

public virtual void Reset()

Extension Points

Required Overrides

Method	Purpose
Draw()	Iterate drawQueue and issue Shapes library draw calls

Optional Overrides

Method	Purpose
Reset()	Additional cleanup beyond clearing the queue. Call base.Reset().

Implementation Requirements

When subclassing ShapeDrawer<TShape>, you MUST:

1. Define a nested readonly struct for TShape with all draw parameters as readonly fields

2. Override Draw() to render all items in drawQueue using the Shapes library

3. Wrap draw calls in Shapes.Draw.PushStyle() / Shapes.Draw.PopStyle() to avoid style leaking

4. Provide a public Add(...) method that creates the struct and enqueues it

You SHOULD:

• Apply lineGeometry and thicknessSpace at the start of Draw() for line-based shapes

• Keep the struct lightweight (value types only, no allocations)

Type Parameters

Parameter	Constraint	Description
TShape	struct	The readonly struct defining the shape's draw parameters (e.g., LineDrawer.Line)

Common Pitfalls

Forgetting PushStyle/PopStyle The Shapes library uses global draw state. Always wrap your Draw() implementation in PushStyle() / PopStyle() to isolate style changes from other drawers.

Shapes persist for one frame only The draw queue is cleared every frame at PRE_UPDATE. To keep a shape visible, you must call the Add() / ShapesDrawer.Draw*() method every frame.

Examples

Custom Shape Drawer

public sealed class DiamondDrawer : ShapeDrawer<DiamondDrawer.Diamond>
{
    public readonly struct Diamond
    {
        public readonly Vector3 Center;
        public readonly float Size;
        public readonly Color Color;

        public Diamond(Vector3 center, float size, Color color)
        {
            Center = center;
            Size = size;
            Color = color;
        }
    }

    public void Add(Vector3 center, float size, Color color)
    {
        drawQueue.Add(new Diamond(center, size, color));
    }

    public override void Draw()
    {
        Shapes.Draw.PushStyle();
        foreach (Diamond diamond in drawQueue)
        {
            // Render diamond using Shapes library calls
        }
        Shapes.Draw.PopStyle();
    }
}

See Also

• ShapesDrawer — the singleton that owns and drives all drawers

• Shapes — concrete drawer implementations

• ShapesDrawer System — system overview