diff --git a/KeepersCompound.Lightmapper/MathUtils.cs b/KeepersCompound.Lightmapper/MathUtils.cs
index 853167b..769fc72 100644
--- a/KeepersCompound.Lightmapper/MathUtils.cs
+++ b/KeepersCompound.Lightmapper/MathUtils.cs
@@ -4,6 +4,49 @@ namespace KeepersCompound.Lightmapper;
 
 public static class MathUtils
 {
+    public readonly struct Aabb
+    {
+        public readonly Vector3 Min;
+        public readonly Vector3 Max;
+
+        public Aabb(Vector3[] points)
+        {
+            Min = new Vector3(float.MaxValue, float.MaxValue, float.MaxValue);
+            Max = new Vector3(float.MinValue, float.MinValue, float.MinValue);
+
+            foreach (var p in points)
+            {
+                Min = Vector3.Min(Min, p);
+                Max = Vector3.Max(Max, p);
+            }
+        }
+    }
+
+    public readonly struct Sphere
+    {
+        public readonly Vector3 Position;
+        public readonly float Radius;
+
+        public Sphere(Vector3 position, float radius)
+        {
+            Position = position;
+            Radius = radius;
+        }
+    }
+
+    public static Vector3 ClosestPoint(Aabb aabb, Vector3 point)
+    {
+        return Vector3.Min(aabb.Max, Vector3.Max(aabb.Min, point));
+    }
+
+    public static bool Intersects(Sphere sphere, Aabb aabb)
+    {
+        var closestPoint = ClosestPoint(aabb, sphere.Position);
+        var d2 = (sphere.Position - closestPoint).LengthSquared();
+        var r2 = sphere.Radius * sphere.Radius;
+        return d2 < r2;
+    }
+
     public static float DistanceFromPlane(Plane plane, Vector3 point)
     {
         return Math.Abs(Vector3.Dot(plane.Normal, point) + plane.D) / plane.Normal.Length();
diff --git a/KeepersCompound.Lightmapper/Program.cs b/KeepersCompound.Lightmapper/Program.cs
index 13d3136..b8c8164 100644
--- a/KeepersCompound.Lightmapper/Program.cs
+++ b/KeepersCompound.Lightmapper/Program.cs
@@ -1,4 +1,4 @@
-using System.Numerics;
+using System.Numerics;
 using KeepersCompound.LGS.Database;
 using KeepersCompound.LGS.Database.Chunks;
 using TinyEmbree;
@@ -22,6 +22,7 @@ class Program
 
         var misPath = "/stuff/Games/thief/drive_c/GOG Games/TG ND 1.27 (MAPPING)/FMs/JAYRUDE_Tests/lm_test.cow";
         misPath = "/stuff/Games/thief/drive_c/GOG Games/TG ND 1.27 (MAPPING)/FMs/AtdV/miss20.mis";
+        misPath = "/stuff/Games/thief/drive_c/GOG Games/TG ND 1.27 (MAPPING)/FMs/TDP20AC_a_burrick_in_a_room/miss20.mis";
         Timing.TimeStage("Total", () => LightmapMission(misPath));
 
         Timing.LogAll();
@@ -246,6 +247,15 @@ class Program
                 topLeft -= renderPoly.TextureVectors.Item1 * (renderPoly.TextureBases.Item1 - info.Bases.Item1 * 0.25f);
                 topLeft -= renderPoly.TextureVectors.Item2 * (renderPoly.TextureBases.Item2 - info.Bases.Item2 * 0.25f);
 
+                var xDir = 0.25f * lightmap.Width * renderPoly.TextureVectors.Item1;
+                var yDir = 0.25f * lightmap.Height * renderPoly.TextureVectors.Item2;
+                var aabb = new MathUtils.Aabb([
+                    topLeft,
+                    topLeft + xDir,
+                    topLeft + yDir,
+                    topLeft + xDir + yDir,
+                ]);
+
                 foreach (var light in lights)
                 {
                     // Check if plane normal is facing towards the light
@@ -266,6 +276,13 @@ class Program
                         continue;
                     }
 
+                    // If the poly of the lightmap doesn't intersect the light radius then
+                    // none of the lightmap points will so we can discard.
+                    if (!MathUtils.Intersects(new MathUtils.Sphere(light.position, light.radius), aabb))
+                    {
+                        continue;
+                    }
+
                     for (var y = 0; y < lightmap.Height; y++)
                     {
                         for (var x = 0; x < lightmap.Width; x++)