Simon Holmberg
Executable
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using Microsoft.Xna.Framework;
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using Microsoft.Xna.Framework.Graphics;
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using Krypton.Common;
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namespace Krypton
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{
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/// <summary>
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/// A hull used for casting shadows from a light source
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/// </summary>
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public class ShadowHull
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{
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#region Orientation
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/// <summary>
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/// The position of the shadow hull
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/// </summary>
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public Vector2 Position;
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/// <summary>
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/// The angle of the shadow hull
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/// </summary>
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public float Angle;
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#endregion
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#region Shape
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/// <summary>
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/// The maximum radius in which all of the shadow hull's vertices are contained, originating from the hull's position
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/// </summary>
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public float MaxRadius;
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/// <summary>
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/// The vertices comprising the shadow hull
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/// </summary>
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public ShadowHullPoint[] Points;
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/// <summary>
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/// The number of vertices comprising the shadow hull
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/// </summary>
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public int NumPoints;
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/// <summary>
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/// The indicies used to render the shadow hull
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/// </summary>
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public Int32[] Indicies;
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/// <summary>
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/// The number of indicies used to render the shadow hull
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/// </summary>
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public int NumIndicies;
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/// <summary>
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/// A value indicating if the hull should cast a shadow
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/// </summary>
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public bool Visible = true;
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/// <summary>
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/// A value indicating how much to stretch the hull
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/// </summary>
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public Vector2 Scale = Vector2.One;
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#endregion
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private ShadowHull(){}
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#region Factory Methods
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/// <summary>
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/// Creates a rectangular shadow hull
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/// </summary>
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/// <param name="size">The dimensions of the rectangle</param>
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/// <returns>A rectangular shadow hull</returns>
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public static ShadowHull CreateRectangle(Vector2 size)
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{
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ShadowHull hull = new ShadowHull();
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size *= 0.5f;
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hull.MaxRadius = (float)Math.Sqrt(size.X * size.X + size.Y * size.Y);
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hull.NumPoints = 4 * 2;
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var numTris = hull.NumPoints - 2;
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hull.NumIndicies = numTris * 3;
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hull.Points = new ShadowHullPoint[hull.NumPoints];
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hull.Indicies = new Int32[hull.NumIndicies];
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// Vertex position
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var posTR = new Vector2(+size.X, +size.Y);
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var posBR = new Vector2(+size.X, -size.Y);
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var posBL = new Vector2(-size.X, -size.Y);
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var posTL = new Vector2(-size.X, +size.Y);
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// Right
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hull.Points[0] = new ShadowHullPoint(posTR, Vector2.UnitX);
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hull.Points[1] = new ShadowHullPoint(posBR, Vector2.UnitX);
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// Bottom
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hull.Points[2] = new ShadowHullPoint(posBR, -Vector2.UnitY);
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hull.Points[3] = new ShadowHullPoint(posBL, -Vector2.UnitY);
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// Left
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hull.Points[4] = new ShadowHullPoint(posBL, -Vector2.UnitX);
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hull.Points[5] = new ShadowHullPoint(posTL, -Vector2.UnitX);
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// Top
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hull.Points[6] = new ShadowHullPoint(posTL, Vector2.UnitY);
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hull.Points[7] = new ShadowHullPoint(posTR, Vector2.UnitY);
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// Create tris
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for (int i = 0; i < numTris; i++)
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{
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hull.Indicies[i * 3 + 0] = 0;
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hull.Indicies[i * 3 + 1] = i + 1;
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hull.Indicies[i * 3 + 2] = i + 2;
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}
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return hull;
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}
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/// <summary>
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/// Creates a circular shadow hull
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/// </summary>
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/// <param name="radius">radius of the circle</param>
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/// <param name="sides">number of sides the circle will be comprised of</param>
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/// <returns>A circular shadow hull</returns>
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public static ShadowHull CreateCircle(float radius, int sides)
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{
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// Validate input
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if (sides < 3) { throw new ArgumentException("Shadow hull must have at least 3 sides."); }
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ShadowHull hull = new ShadowHull();
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hull.MaxRadius = radius;
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// Calculate number of sides
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hull.NumPoints = sides * 2;
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var numTris = hull.NumPoints - 2;
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hull.NumIndicies = numTris * 3;
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hull.Points = new ShadowHullPoint[hull.NumPoints];
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hull.Indicies = new Int32[hull.NumIndicies];
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var angle = (float)(-Math.PI * 2) / sides; // XNA Renders Clockwise
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var angleOffset = angle / 2;
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for (int i = 0; i < sides; i++)
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{
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// Create vertices
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var v1 = new ShadowHullPoint();
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var v2 = new ShadowHullPoint();
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// Vertex Position
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v1.Position.X = (float)Math.Cos(angle * i) * radius;
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v1.Position.Y = (float)Math.Sin(angle * i) * radius;
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v2.Position.X = (float)Math.Cos(angle * (i + 1)) * radius;
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v2.Position.Y = (float)Math.Sin(angle * (i + 1)) * radius;
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// Vertex Normal
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v1.Normal.X = (float)Math.Cos(angle * i + angleOffset);
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v1.Normal.Y = (float)Math.Sin(angle * i + angleOffset);
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v2.Normal.X = (float)Math.Cos(angle * i + angleOffset);
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v2.Normal.Y = (float)Math.Sin(angle * i + angleOffset);
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// Copy vertices
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hull.Points[i * 2 + 0] = v1;
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hull.Points[i * 2 + 1] = v2;
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}
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for (int i = 0; i < numTris; i++)
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{
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hull.Indicies[i * 3 + 0] = 0;
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hull.Indicies[i * 3 + 1] = (Int32)(i + 1);
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hull.Indicies[i * 3 + 2] = (Int32)(i + 2);
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}
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return hull;
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}
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/// <summary>
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/// Creates a custom shadow hull based on a series of vertices
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/// </summary>
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/// <param name="points">The points which the shadow hull will be comprised of</param>
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/// <returns>A custom shadow hulll</returns>
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public static ShadowHull CreateConvex(ref Vector2[] points)
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{
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// Validate input
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if (points == null) { throw new ArgumentNullException("Points cannot be null."); }
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if (points.Length < 3) { throw new ArgumentException("Need at least 3 points to create shadow hull."); }
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var numPoints = points.Length;
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ShadowHull hull = new ShadowHull();
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hull.NumPoints = numPoints * 2;
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var numTris = hull.NumPoints - 2;
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hull.NumIndicies = numTris * 3;
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hull.Points = new ShadowHullPoint[hull.NumPoints];
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hull.Indicies = new Int32[hull.NumIndicies];
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Vector2 pointMin = points[0];
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Vector2 pointMax = points[0];
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for (int i = 0; i < numPoints; i++)
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{
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var p1 = points[(i + 0) % numPoints];
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var p2 = points[(i + 1) % numPoints];
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hull.MaxRadius = Math.Max(hull.MaxRadius, p1.Length());
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var line = p2 - p1;
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var normal = new Vector2(-line.Y, +line.X);
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normal.Normalize();
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hull.Points[i * 2 + 0] = new ShadowHullPoint(p1, normal);
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hull.Points[i * 2 + 1] = new ShadowHullPoint(p2, normal);
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}
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for (Int32 i = 0; i < numTris; i++)
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{
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hull.Indicies[i * 3 + 0] = 0;
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hull.Indicies[i * 3 + 1] = (Int32)(i + 1);
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hull.Indicies[i * 3 + 2] = (Int32)(i + 2);
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}
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return hull;
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}
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#endregion
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}
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}
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