fix(GLTFImporter): fix GLTF Draco normals

fix #3192

Author: daker

Sources/IO/Geometry/GLTFImporter/Extensions.js

@@ -2,6 +2,7 @@ import macro from 'vtk.js/Sources/macros';
 import * as vtkMath from 'vtk.js/Sources/Common/Core/Math';
 import vtkDracoReader from 'vtk.js/Sources/IO/Geometry/DracoReader';
 import vtkLight from 'vtk.js/Sources/Rendering/Core/Light';
+import vtkPolyDataNormals from 'vtk.js/Sources/Filters/Core/PolyDataNormals';
 
 import { MIN_LIGHT_ATTENUATION } from 'vtk.js/Sources/IO/Geometry/GLTFImporter/Constants';
 
@@ -89,7 +90,10 @@ export function handleKHRLightsPunctual(extension, transformMatrix, model) {
 export async function handleKHRDracoMeshCompression(extension) {
   const reader = vtkDracoReader.newInstance();
   reader.parse(extension.bufferView);
-  return reader.getOutputData();
+  const pdn = vtkPolyDataNormals.newInstance();
+  pdn.setInputConnection(reader.getOutputPort());
+  pdn.setComputePointNormals(true);
+  return pdn.getOutputData();
 }
 
 /**