Fix OBJ mesh index buffer overflow by using UNSIGNED_INT for large models (#148)

Author: MustafaMulla29

lib/gltf/buffer-builder.ts

@@ -67,6 +67,16 @@ export class BufferBuilder {
     return byteOffset
   }
 
+  addUint32Array(values: number[]): number {
+    const byteOffset = this.offset
+    this.ensureCapacity(values.length * 4)
+    for (const value of values) {
+      this.view.setUint32(this.offset, value, true)
+      this.offset += 4
+    }
+    return byteOffset
+  }
+
   addBytes(bytes: Uint8Array): number {
     const byteOffset = this.offset
     this.ensureCapacity(bytes.length)

lib/gltf/gltf-builder.ts

@@ -239,7 +239,7 @@ export class GLTFBuilder {
       const indicesAccessorIndex = this.addAccessor(
         transformedMeshData.indices,
         "SCALAR",
-        COMPONENT_TYPE.UNSIGNED_SHORT,
+        COMPONENT_TYPE.UNSIGNED_INT,
         TARGET.ELEMENT_ARRAY_BUFFER,
       )
 
@@ -722,6 +722,9 @@ export class GLTFBuilder {
     } else if (componentType === COMPONENT_TYPE.UNSIGNED_SHORT) {
       byteOffset = this.bufferBuilder.addUint16Array(data)
       byteLength = data.length * 2
+    } else if (componentType === COMPONENT_TYPE.UNSIGNED_INT) {
+      byteOffset = this.bufferBuilder.addUint32Array(data)
+      byteLength = data.length * 4
     } else {
       throw new Error(`Unsupported component type: ${componentType}`)
     }