sneak/SharedTests/GeometryTests.cs

using Microsoft.Xna.Framework;
using System;
using Xunit;

namespace SemiColinGames.Tests {
  public class GeometryTests {

    private void AssertVectorsEqual(Vector2 v1, Vector2 v2) {
      Assert.Equal(v1.X, v2.X, 5);
      Assert.Equal(v1.Y, v2.Y, 5);
    }

    [Fact]
    public void TestVector2Rotate() {
      Vector2 v = new Vector2(10, 0);
      AssertVectorsEqual(new Vector2(10, 0), v.Rotate(FMath.DegToRad(0)));
      AssertVectorsEqual(new Vector2(0, 10), v.Rotate(FMath.DegToRad(90)));
      AssertVectorsEqual(new Vector2(-10, 0), v.Rotate(FMath.DegToRad(180)));
      AssertVectorsEqual(new Vector2(0, -10), v.Rotate(FMath.DegToRad(270)));
      AssertVectorsEqual(new Vector2(10, 0), v.Rotate(FMath.DegToRad(360)));
      AssertVectorsEqual(new Vector2(0, 10), v.Rotate(FMath.DegToRad(450)));

      AssertVectorsEqual(new Vector2(0, -10), v.Rotate(FMath.DegToRad(-90)));
      AssertVectorsEqual(new Vector2(-10, 0), v.Rotate(FMath.DegToRad(-180)));
      AssertVectorsEqual(new Vector2(0, 10), v.Rotate(FMath.DegToRad(-270)));
      AssertVectorsEqual(new Vector2(10, 0), v.Rotate(FMath.DegToRad(-360)));
      AssertVectorsEqual(new Vector2(0, -10), v.Rotate(FMath.DegToRad(-450)));

      AssertVectorsEqual(new Vector2(7.0710678f, 7.0710678f), v.Rotate(FMath.DegToRad(45)));
      AssertVectorsEqual(new Vector2(8.6602540f, 5f), v.Rotate(FMath.DegToRad(30)));
      AssertVectorsEqual(new Vector2(5f, 8.6602540f), v.Rotate(FMath.DegToRad(60)));
      AssertVectorsEqual(new Vector2(-5f, 8.6602540f), v.Rotate(FMath.DegToRad(120)));
      AssertVectorsEqual(new Vector2(-8.6602540f, 5f), v.Rotate(FMath.DegToRad(150)));

      AssertVectorsEqual(new Vector2(7.0710678f, -7.0710678f), v.Rotate(FMath.DegToRad(-45)));
      AssertVectorsEqual(new Vector2(8.6602540f, -5f), v.Rotate(FMath.DegToRad(-30)));
      AssertVectorsEqual(new Vector2(5f, -8.6602540f), v.Rotate(FMath.DegToRad(-60)));
      AssertVectorsEqual(new Vector2(-5f, -8.6602540f), v.Rotate(FMath.DegToRad(-120)));
      AssertVectorsEqual(new Vector2(-8.6602540f, -5f), v.Rotate(FMath.DegToRad(-150)));
    }

    [Fact]
    public void TestIntersectSegmentNotColliding() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      Assert.Null(box.IntersectSegment(new Vector2(-16, -16), new Vector2(32, 0)));
    }

    [Fact]
    public void TestIntersectSegmentHit() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      var point = new Vector2(-16, 4);
      var delta = new Vector2(32, 0);
      Hit? maybeHit = box.IntersectSegment(point, delta);

      Assert.NotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.Equal(box, hit.Collider);
      Assert.Equal(0.25, hit.Time);

      Assert.Equal(point.X + delta.X * hit.Time, hit.Position.X);
      Assert.Equal(point.Y + delta.Y * hit.Time, hit.Position.Y);

      Assert.Equal((1.0f - hit.Time) * -delta.X, hit.Delta.X);
      Assert.Equal((1.0f - hit.Time) * -delta.Y, hit.Delta.Y);

      Assert.Equal(-1, hit.Normal.X);
      Assert.Equal(0, hit.Normal.Y);
    }

    [Fact]
    public void TestIntersectSegmentFromInsideBox() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      var point = new Vector2(-4, 4);
      var delta = new Vector2(32, 0);
      Hit? maybeHit = box.IntersectSegment(point, delta);

      Assert.NotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.Equal(box, hit.Collider);
      Assert.Equal(0.0, hit.Time);

      Assert.Equal(-4, hit.Position.X);
      Assert.Equal(4, hit.Position.Y);

      Assert.Equal(-delta.X, hit.Delta.X);
      Assert.Equal(-delta.Y, hit.Delta.Y);

      Assert.Equal(-1, hit.Normal.X);
      Assert.Equal(0, hit.Normal.Y);
    }

    [Fact]
    public void TestIntersectSegmentWithPadding() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(8, 8));
      var point = new Vector2(-16, 4);
      var delta = new Vector2(32, 0);
      int padding = 4;
      Hit? maybeHit = box.IntersectSegment(point, delta, new Vector2(padding, padding));

      Assert.NotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.Equal(box, hit.Collider);
      Assert.Equal(0.125, hit.Time);

      Assert.Equal(point.X + delta.X * hit.Time, hit.Position.X);
      Assert.Equal(point.Y + delta.Y * hit.Time, hit.Position.Y);

      Assert.Equal((1.0f - hit.Time) * -delta.X, hit.Delta.X);
      Assert.Equal((1.0f - hit.Time) * -delta.Y, hit.Delta.Y);

      Assert.Equal(-1, hit.Normal.X);
      Assert.Equal(0, hit.Normal.Y);
    }

    [Fact]
    public void TestIntersectSegmentFromTwoDirections() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(32, 32));
      var farPos = new Vector2(64, 0);
      var farToNearDelta = new Vector2(-32, 0);
      Assert.Null(box.IntersectSegment(farPos, farToNearDelta));

      var nearPos = new Vector2(32, 0);
      var nearToFarDelta = new Vector2(32, 0);
      Assert.Null(box.IntersectSegment(nearPos, nearToFarDelta));
    }

    [Fact]
    public void TestIntersectSegmentXAxisAligned() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(16, 16));
      var pos = new Vector2(-32, 0);
      var delta = new Vector2(64, 0);
      Hit? maybeHit = box.IntersectSegment(pos, delta);

      Assert.NotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.Equal(0.25, hit.Time);
      Assert.Equal(-1, hit.Normal.X);
      Assert.Equal(0, hit.Normal.Y);
    }

    [Fact]
    public void TestIntersectSegmentYAxisAligned() {
      AABB box = new AABB(new Vector2(0, 0), new Vector2(16, 16));
      var pos = new Vector2(0, -32);
      var delta = new Vector2(0, 64);
      Hit? maybeHit = box.IntersectSegment(pos, delta);

      Assert.NotNull(maybeHit);
      Hit hit = (Hit) maybeHit;

      Assert.Equal(0.25, hit.Time);
      Assert.Equal(0, hit.Normal.X);
      Assert.Equal(-1, hit.Normal.Y);
    }
  }
}