mrgameeng/tests/MrGameEng.Graphics.Tests/LightmapBuilderTests.cs

using Microsoft.Xna.Framework;
using MrGameEng.Lighting;
using Xunit;

namespace MrGameEng.Lighting.Tests;

public class LightmapBuilderTests
{
    private static float[] Build(
        int width,
        int height,
        float ambient,
        bool[] occluders,
        params LightSample[] lights
    )
    {
        var light = new float[width * height];
        LightmapBuilder.Build(light, width, height, ambient, occluders, lights);
        return light;
    }

    [Fact]
    public void Ambient_WithoutOccluders_IsUniform()
    {
        var light = Build(4, 4, 0.6f, new bool[16]);
        Assert.All(light, v => Assert.Equal(0.6f, v, 5));
    }

    [Fact]
    public void OccluderCell_IsDarkerThanOpenCell()
    {
        var occ = new bool[9];
        occ[4] = true; // centre cell shaded
        var light = Build(3, 3, 0.8f, occ);
        Assert.True(light[4] < light[0]);
        Assert.Equal(0.8f * LightmapBuilder.OccluderShade, light[4], 5);
    }

    [Fact]
    public void PointLight_IsBrighterNearSourceAndFadesToRadius()
    {
        var light = Build(7, 1, 0f, new bool[7], new LightSample(0, 0, 6f, 1f));
        Assert.True(light[0] > light[2] && light[2] > light[5]);
        Assert.InRange(light[6], 0f, 0.01f); // на радиусе свет угасает
    }

    [Fact]
    public void Occluder_CastsShadowBehindIt()
    {
        var occ = new bool[7];
        occ[3] = true; // препятствие между источником (0) и дальними клетками
        var light = Build(7, 1, 0f, occ, new LightSample(0, 0, 10f, 1f));

        Assert.True(light[1] > 0f); // перед препятствием — освещено
        Assert.Equal(0f, light[5], 5); // за препятствием — тень
    }

    [Fact]
    public void SunShadow_DarkensCellsInTheShadowDirection_FadingFromTheCaster()
    {
        var occ = new bool[7];
        occ[3] = true; // occluder in the middle
        var light = new float[7];
        LightmapBuilder.Build(
            light,
            7,
            1,
            1f,
            occ,
            [],
            sunShadow: new Vector2(3f, 0f),
            sunShadowStrength: 0.6f
        );

        Assert.Equal(1f, light[2], 5); // toward the sun (opposite the shadow) — unshadowed
        Assert.Equal(LightmapBuilder.OccluderShade, light[3], 5); // occluder cell stays self-shaded
        Assert.True(light[4] < 1f); // in shadow
        Assert.True(light[4] < light[6]); // darker near the caster, fading along the shadow
    }

    [Fact]
    public void Values_StayWithinUnitRange()
    {
        var light = Build(
            5,
            5,
            0.5f,
            new bool[25],
            new LightSample(2, 2, 4f, 2f) // яркий свет — проверяем клампинг
        );
        Assert.All(light, v => Assert.InRange(v, 0f, 1f));
    }
}