From afadfb2ea8a3fd708a8204280e99dab31359c39f Mon Sep 17 00:00:00 2001
From: sudhir <sudhir9297@gmail.com>
Date: Mon, 11 May 2026 11:24:44 +0530
Subject: [PATCH] Guard viewer BVH against empty geometries

---
 .../viewer/src/components/viewer/index.tsx    |   6 +-
 .../src/components/viewer/scene-bvh.tsx       | 137 ++++++++++++++++++
 2 files changed, 140 insertions(+), 3 deletions(-)
 create mode 100644 packages/viewer/src/components/viewer/scene-bvh.tsx

diff --git a/packages/viewer/src/components/viewer/index.tsx b/packages/viewer/src/components/viewer/index.tsx
index bc2b5b85..f4d9bd9b 100644
--- a/packages/viewer/src/components/viewer/index.tsx
+++ b/packages/viewer/src/components/viewer/index.tsx
@@ -1,6 +1,5 @@
 'use client'
 
-import { Bvh } from '@react-three/drei'
 import { Canvas, extend, type ThreeToJSXElements, useFrame, useThree } from '@react-three/fiber'
 import { useEffect, useMemo, useRef } from 'react'
 import * as THREE from 'three/webgpu'
@@ -28,6 +27,7 @@ import FrameLimiter from './frame-limiter'
 import { Lights } from './lights'
 import { PerfMonitor } from './perf-monitor'
 import PostProcessing, { DEFAULT_HOVER_STYLES, type HoverStyles } from './post-processing'
+import { SceneBvh } from './scene-bvh'
 import { SelectionManager } from './selection-manager'
 import { ViewerCamera } from './viewer-camera'
 
@@ -216,9 +216,9 @@ const Viewer: React.FC<ViewerProps> = ({
         {/* <directionalLight position={[10, 10, 5]} intensity={0.5} castShadow
           /> */}
         <Lights />
-        <Bvh>
+        <SceneBvh>
           <SceneRenderer />
-        </Bvh>
+        </SceneBvh>
 
         {/* Default Systems */}
         <LevelSystem />
diff --git a/packages/viewer/src/components/viewer/scene-bvh.tsx b/packages/viewer/src/components/viewer/scene-bvh.tsx
new file mode 100644
index 00000000..c4517e6b
--- /dev/null
+++ b/packages/viewer/src/components/viewer/scene-bvh.tsx
@@ -0,0 +1,137 @@
+import { useThree } from '@react-three/fiber'
+import {
+  type ReactNode,
+  forwardRef,
+  useEffect,
+  useImperativeHandle,
+  useRef,
+} from 'react'
+import { Group, Mesh, type BufferGeometry } from 'three'
+import {
+  SAH,
+  acceleratedRaycast,
+  computeBoundsTree,
+  disposeBoundsTree,
+  type SplitStrategy,
+} from 'three-mesh-bvh'
+
+type SceneBvhProps = {
+  children?: ReactNode
+  enabled?: boolean
+  firstHitOnly?: boolean
+  strategy?: SplitStrategy
+  verbose?: boolean
+  setBoundingBox?: boolean
+  maxDepth?: number
+  maxLeafSize?: number
+  indirect?: boolean
+}
+
+const isMesh = (object: unknown): object is Mesh =>
+  !!object && typeof object === 'object' && (object as Mesh).isMesh === true
+
+const hasBvhCompatibleGeometry = (geometry?: BufferGeometry | null) => {
+  if (!geometry) return false
+
+  const position = geometry.getAttribute('position')
+  if (!position) return false
+
+  const vertexCount = geometry.getIndex()?.count ?? position.count
+  return vertexCount >= 3
+}
+
+export const SceneBvh = forwardRef<Group, SceneBvhProps>(
+  (
+    {
+      children,
+      enabled = true,
+      firstHitOnly = false,
+      strategy = SAH,
+      verbose = false,
+      setBoundingBox = true,
+      maxDepth = 40,
+      maxLeafSize = 10,
+      indirect = false,
+    },
+    forwardedRef,
+  ) => {
+    const ref = useRef<Group>(null)
+    const raycaster = useThree((state) => state.raycaster)
+
+    useImperativeHandle(forwardedRef, () => ref.current!, [])
+
+    useEffect(() => {
+      if (!enabled || !ref.current) return
+
+      const options = {
+        strategy,
+        verbose,
+        setBoundingBox,
+        maxDepth,
+        maxLeafSize,
+        indirect,
+      }
+      const group = ref.current
+      const acceleratedMeshes = new Set<Mesh>()
+      const computedGeometries = new Set<BufferGeometry>()
+
+      ;(raycaster as any).firstHitOnly = firstHitOnly
+
+      group.traverse((child) => {
+        if (!isMesh(child)) return
+
+        if (child.raycast === Mesh.prototype.raycast) {
+          child.raycast = acceleratedRaycast
+          acceleratedMeshes.add(child)
+        }
+
+        if (child.raycast !== acceleratedRaycast) return
+
+        const geometry = child.geometry
+        if (geometry.boundsTree || !hasBvhCompatibleGeometry(geometry)) return
+
+        try {
+          geometry.computeBoundsTree = computeBoundsTree
+          geometry.disposeBoundsTree = disposeBoundsTree
+          geometry.computeBoundsTree(options)
+          computedGeometries.add(geometry)
+        } catch (error) {
+          console.warn('[viewer] Skipping BVH for incompatible mesh geometry.', {
+            mesh: child.name || child.type,
+            error,
+          })
+        }
+      })
+
+      return () => {
+        delete (raycaster as any).firstHitOnly
+
+        for (const geometry of computedGeometries) {
+          if (geometry.boundsTree) {
+            geometry.disposeBoundsTree()
+          }
+        }
+
+        for (const mesh of acceleratedMeshes) {
+          if (mesh.raycast === acceleratedRaycast) {
+            mesh.raycast = Mesh.prototype.raycast
+          }
+        }
+      }
+    }, [
+      enabled,
+      firstHitOnly,
+      strategy,
+      verbose,
+      setBoundingBox,
+      maxDepth,
+      maxLeafSize,
+      indirect,
+      raycaster,
+    ])
+
+    return <group ref={ref}>{children}</group>
+  },
+)
+
+SceneBvh.displayName = 'SceneBvh'