Culling function

Test is currently empty because I don't know how to pass the camera

Author: Kuba663

src/main/java/com/cleanroommc/kirino/engine/render/geometry/component/MeshletComponent.java

@@ -11,6 +11,8 @@
 import org.joml.Vector4f;
 import org.jspecify.annotations.NonNull;
 
+import java.util.Arrays;
+
 @CleanComponent
 public class MeshletComponent implements ICleanComponent {
     public AABB aabb;
@@ -65,6 +67,8 @@ public static boolean cull(@NonNull MeshletComponent meshlet,
         Vector3f direction = new Vector3f();
         Vector4f tmp = new Vector4f();
 
+        boolean isFront = false, isOutsideView = true;
+
         // Bounding box points
         Vector3f[] points = {
                 // Meshlet
@@ -87,14 +91,41 @@ public static boolean cull(@NonNull MeshletComponent meshlet,
                 new Vector3f(aabb.xMax, aabb.yMax, aabb.zMax)
         };
 
+        Integer[] indices = new Integer[16];
+
+        for (int i = 0; i < indices.length; i++) {
+            indices[i] = i;
+        }
+
         // Convert points to use camera origin as (0;0)
         for (int i = 0; i < points.length; i++) {
             points[i].sub(camera.getWorldOffset(), points[i]);
         }
 
+        Arrays.sort(indices, (a, b) -> (int) (points[a].lengthSquared()-points[b].lengthSquared()));
+
+        for (int i = 0; i < 8; i++) {
+            if (indices[i] >= 8) {
+                isFront = true;
+                break;
+            }
+        }
+
+        if (!isFront) {
+            return true;
+        }
+
         camera.getViewRotationMatrix().getColumn(2, tmp);
         tmp.xyz(direction);
 
-        return true;
+        direction.normalize(); // not sure if I need to do that
+        for (int i = 8; i < points.length; i++) {
+            float simm = direction.dot(points[i])/(direction.length()*points[i].length());
+            if (simm < 0.f) {
+                return true;
+            }
+        }
+
+        return false;
     }
 }

src/test/java/com/cleanroommc/test/kirino/meshlet/CullingTest.java

@@ -0,0 +1,30 @@
+package com.cleanroommc.test.kirino.meshlet;
+
+import com.cleanroommc.kirino.engine.render.geometry.AABB;
+import com.cleanroommc.kirino.engine.render.geometry.component.MeshletComponent;
+import it.unimi.dsi.fastutil.objects.ObjectArrayList;
+import org.joml.Vector3f;
+import org.junit.Before;
+
+import java.util.List;
+
+public class CullingTest {
+
+    private List<MeshletAABBPair> meshlets = new ObjectArrayList<>();
+
+    @Before
+    public void setup() {
+        for (int i = 0; i < 36; i++) {
+            float multiplier = i % 2 == 0 ? 0.25f : 1.75f;
+            Vector3f baseAABBPosition = new Vector3f((float) Math.sin(multiplier*10*i), (float) Math.cos(multiplier*10*i), 0.f);
+            Vector3f baseMeshletPoint = new Vector3f((float) Math.sin(10*i), (float) Math.cos(10*i), 0.f);
+            MeshletComponent component = new MeshletComponent();
+            component.transparent = false;
+            component.aabb = new AABB(baseMeshletPoint.x, baseMeshletPoint.y, baseMeshletPoint.z, baseMeshletPoint.x+ 3.f, baseMeshletPoint.y + 3.f, baseMeshletPoint.z + 3.f);
+            AABB entity = new AABB(baseAABBPosition.x, baseAABBPosition.y, baseAABBPosition.z, baseAABBPosition.x+ 1.f, baseAABBPosition.y + 1.f, baseAABBPosition.z + 1.f);
+            meshlets.add(new MeshletAABBPair(component, entity, i % 2 == 0));
+        }
+    }
+
+    private record MeshletAABBPair(MeshletComponent meshlet, AABB aabb, boolean expectedCullingResult) {}
+}