295 lines
12 KiB
C#
295 lines
12 KiB
C#
using System.Collections;
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using System.Collections.Generic;
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using Syntriax.Engine.Core;
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using Syntriax.Engine.Core.Abstract;
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namespace Syntriax.Engine.Physics2D.Primitives;
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/// <summary>
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/// Represents a shape defined by a collection of vertices.
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/// </summary>
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/// <param name="vertices">The vertices of the shape.</param>
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/// <remarks>
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/// Initializes a new instance of the <see cref="Shape"/> struct with the specified vertices.
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/// </remarks>
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[System.Diagnostics.DebuggerDisplay("Vertices Count: {Vertices.Count}")]
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public readonly struct Shape(List<Vector2D> vertices) : IEnumerable<Vector2D>
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{
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public static readonly Shape Triangle = CreateNgon(3, Vector2D.Up);
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public static readonly Shape Box = CreateNgon(4, Vector2D.One);
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public static readonly Shape Pentagon = CreateNgon(5, Vector2D.Up);
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public static readonly Shape Hexagon = CreateNgon(6, Vector2D.Right);
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private readonly List<Vector2D> _verticesList = vertices;
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/// <summary>
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/// Gets the vertices of the shape.
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/// </summary>
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public IReadOnlyList<Vector2D> Vertices => _verticesList;
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/// <summary>
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/// The vertex at the specified index.
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/// </summary>
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/// <param name="index">The zero-based index of the vertex to get or set.</param>
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/// <returns>The vertex at the specified index.</returns>
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public Vector2D this[System.Index index] => Vertices[index];
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/// <summary>
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/// Returns a copy of the current shape.
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/// </summary>
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/// <param name="shape">The shape to copy.</param>
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/// <returns>A copy of the input shape.</returns>
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public static Shape CreateCopy(Shape shape) => new(new List<Vector2D>(shape.Vertices));
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/// <summary>
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/// Creates a regular polygon (ngon) with the specified number of vertices.
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/// </summary>
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/// <param name="vertexCount">The number of vertices in the polygon.</param>
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/// <returns>A regular polygon with the specified number of vertices.</returns>
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public static Shape CreateNgon(int vertexCount) => CreateNgon(vertexCount, Vector2D.Up);
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/// <summary>
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/// Creates a regular polygon (ngon) with the specified number of vertices and a rotation position.
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/// </summary>
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/// <param name="vertexCount">The number of vertices in the polygon.</param>
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/// <param name="positionToRotate">The position to use for rotation.</param>
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/// <returns>A regular polygon with the specified number of vertices and rotation position.</returns>
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public static Shape CreateNgon(int vertexCount, Vector2D positionToRotate)
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{
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if (vertexCount < 3)
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throw new System.ArgumentException($"{nameof(vertexCount)} must have a value of more than 2.");
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List<Vector2D> vertices = new(vertexCount);
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float radiansPerVertex = 360f / vertexCount * Math.DegreeToRadian;
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for (int i = 0; i < vertexCount; i++)
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vertices.Add(positionToRotate.Rotate(i * radiansPerVertex));
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return new(vertices);
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}
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/// <summary>
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/// Gets the super triangle that encloses the given shape.
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/// </summary>
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/// <param name="shape">The shape to enclose.</param>
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/// <returns>The super triangle that encloses the given shape.</returns>
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public static Triangle GetSuperTriangle(Shape shape)
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{
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float minX = float.MaxValue, minY = float.MaxValue;
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float maxX = float.MinValue, maxY = float.MinValue;
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foreach (Vector2D point in shape.Vertices)
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{
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minX = Math.Min(minX, point.X);
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minY = Math.Min(minY, point.Y);
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maxX = Math.Max(maxX, point.X);
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maxY = Math.Max(maxY, point.Y);
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}
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float dx = maxX - minX;
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float dy = maxY - minY;
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float deltaMax = Math.Max(dx, dy);
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float midX = (minX + maxX) / 2;
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float midY = (minY + maxY) / 2;
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Vector2D p1 = new((float)midX - 20f * (float)deltaMax, (float)midY - (float)deltaMax);
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Vector2D p2 = new((float)midX, (float)midY + 20 * (float)deltaMax);
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Vector2D p3 = new((float)midX + 20 * (float)deltaMax, (float)midY - (float)deltaMax);
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return new Triangle(p1, p2, p3);
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}
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/// <summary>
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/// Gets the lines that form the edges of the shape.
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/// </summary>
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/// <param name="shape">The shape to get lines from.</param>
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/// <param name="lines">The list to populate with lines.</param>
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public static void GetLines(Shape shape, IList<Line> lines)
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{
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lines.Clear();
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for (int i = 0; i < shape.Vertices.Count - 1; i++)
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lines.Add(new(shape.Vertices[i], shape.Vertices[i + 1]));
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lines.Add(new(shape.Vertices[^1], shape.Vertices[0]));
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}
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/// <summary>
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/// Gets a list of lines that form the edges of the shape.
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/// </summary>
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/// <param name="shape">The shape to get lines from.</param>
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/// <returns>A list of lines that form the edges of the shape.</returns>
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public static List<Line> GetLines(Shape shape)
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{
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List<Line> lines = new(shape.Vertices.Count - 1);
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GetLines(shape, lines);
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return lines;
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}
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/// <summary>
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/// Projects the shape onto a vector.
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/// </summary>
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/// <param name="shape">The shape to project.</param>
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/// <param name="projectionVector">The vector to project onto.</param>
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/// <param name="list">The list to populate with projected values.</param>
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public static void Project(Shape shape, Vector2D projectionVector, IList<float> list)
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{
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list.Clear();
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int count = shape.Vertices.Count;
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for (int i = 0; i < count; i++)
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list.Add(projectionVector.Dot(shape[i]));
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}
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/// <summary>
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/// Projects the shape onto a vector.
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/// </summary>
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/// <param name="shape">The shape to project.</param>
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/// <param name="projectionVector">The vector to project onto.</param>
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/// <returns>The projection of the shape onto the vector.</returns>
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public static Projection Project(Shape shape, Vector2D projectionVector)
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{
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float min = float.MaxValue;
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float max = float.MinValue;
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for (int i = 0; i < shape.Vertices.Count; i++)
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{
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float projectedLength = projectionVector.Dot(shape.Vertices[i]);
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min = Math.Min(projectedLength, min);
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max = Math.Max(projectedLength, max);
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}
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return new(min, max);
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}
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/// <summary>
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/// Transforms the shape using the specified transform.
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/// </summary>
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/// <param name="shape">The shape to transform.</param>
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/// <param name="transform">The transform to apply.</param>
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/// <returns>The transformed shape.</returns>
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public static Shape TransformShape(Shape shape, ITransform transform)
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{
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List<Vector2D> vertices = new(shape.Vertices.Count);
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int count = shape.Vertices.Count;
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for (int i = 0; i < count; i++)
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vertices.Add(transform.TransformVector2D(shape[i]));
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return new Shape(vertices);
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}
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/// <summary>
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/// Transforms the shape using the specified transform.
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/// </summary>
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/// <param name="from">The shape to transform.</param>
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/// <param name="transform">The transform to apply.</param>
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/// <param name="to">The transformed shape.</param>
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public static void TransformShape(Shape from, ITransform transform, ref Shape to)
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{
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to._verticesList.Clear();
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int count = from._verticesList.Count;
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for (int i = 0; i < count; i++)
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to._verticesList.Add(transform.TransformVector2D(from[i]));
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}
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/// <summary>
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/// Determines whether two shapes are approximately equal.
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/// </summary>
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/// <param name="left">The first shape to compare.</param>
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/// <param name="right">The second shape to compare.</param>
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/// <returns><c>true</c> if the shapes are approximately equal; otherwise, <c>false</c>.</returns>
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public static bool ApproximatelyEquals(Shape left, Shape right)
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{
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if (left.Vertices.Count != right.Vertices.Count)
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return false;
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for (int i = 0; i < left.Vertices.Count; i++)
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if (!left.Vertices[i].ApproximatelyEquals(right.Vertices[i]))
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return false;
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return true;
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}
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/// <inheritdoc/>
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public IEnumerator<Vector2D> GetEnumerator() => Vertices.GetEnumerator();
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/// <inheritdoc/>
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IEnumerator IEnumerable.GetEnumerator() => Vertices.GetEnumerator();
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}
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/// <summary>
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/// Provides extension methods for the <see cref="Shape"/> struct.
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/// </summary>
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public static class ShapeExtensions
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{
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/// <summary>
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/// Creates a copy of the shape.
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/// </summary>
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/// <param name="shape">The shape to copy.</param>
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/// <returns>A copy of the input shape.</returns>
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public static Shape CreateCopy(this Shape shape) => Shape.CreateCopy(shape);
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/// <summary>
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/// Gets the super triangle that encloses the shape.
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/// </summary>
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/// <param name="shape">The shape to enclose.</param>
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/// <returns>The super triangle that encloses the shape.</returns>
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public static Triangle ToSuperTriangle(this Shape shape) => Shape.GetSuperTriangle(shape);
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/// <summary>
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/// Gets the lines that form the edges of the shape.
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/// </summary>
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/// <param name="shape">The shape to get lines from.</param>
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/// <param name="lines">The list to populate with lines.</param>
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public static void ToLines(this Shape shape, IList<Line> lines) => Shape.GetLines(shape, lines);
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/// <summary>
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/// Gets a list of lines that form the edges of the shape.
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/// </summary>
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/// <param name="shape">The shape to get lines from.</param>
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/// <returns>A list of lines that form the edges of the shape.</returns>
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public static List<Line> ToLines(this Shape shape) => Shape.GetLines(shape);
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/// <summary>
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/// Projects the shape onto a vector.
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/// </summary>
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/// <param name="shape">The shape to project.</param>
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/// <param name="projectionVector">The vector to project onto.</param>
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/// <param name="list">The list to populate with projected values.</param>
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public static void ToProjection(this Shape shape, Vector2D projectionVector, IList<float> list) => Shape.Project(shape, projectionVector, list);
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/// <summary>
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/// Projects the shape onto a vector.
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/// </summary>
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/// <param name="shape">The shape to project.</param>
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/// <param name="projectionVector">The vector to project onto.</param>
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/// <returns>The projection of the shape onto the vector.</returns>
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public static Projection ToProjection(this Shape shape, Vector2D projectionVector) => Shape.Project(shape, projectionVector);
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/// <summary>
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/// Transforms the shape using the specified transform.
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/// </summary>
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/// <param name="transform">The transform to apply.</param>
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/// <param name="shape">The shape to transform.</param>
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/// <returns>The transformed shape.</returns>
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public static Shape TransformShape(this ITransform transform, Shape shape) => Shape.TransformShape(shape, transform);
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/// <summary>
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/// Transforms the shape using the specified transform.
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/// </summary>
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/// <param name="transform">The transform to apply.</param>
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/// <param name="from">The shape to transform.</param>
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/// <param name="to">The transformed shape.</param>
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public static void TransformShape(this ITransform transform, Shape from, ref Shape to) => Shape.TransformShape(from, transform, ref to);
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/// <summary>
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/// Determines whether two shapes are approximately equal.
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/// </summary>
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/// <param name="left">The first shape to compare.</param>
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/// <param name="right">The second shape to compare.</param>
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/// <returns><c>true</c> if the shapes are approximately equal; otherwise, <c>false</c>.</returns>
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public static bool ApproximatelyEquals(this Shape left, Shape right) => Shape.ApproximatelyEquals(left, right);
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}
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