Fix OBJ unlit color space (#3147)

Author: Meakk

application/testing/tests.native.cmake

@@ -1,6 +1,7 @@
 ## Tests file formats from native plugin
 f3d_test(NAME TestPLY DATA suzanne.ply)
 f3d_test(NAME TestOBJ DATA world.obj)
+f3d_test(NAME TestOBJUnlit DATA cube_unlit.obj)
 f3d_test(NAME TestSTL DATA suzanne.stl)
 f3d_test(NAME TestVTICell DATA waveletMaterial.vti ARGS -s --coloring-array=Material -c --roughness=1)
 f3d_test(NAME TestVTU DATA dragon.vtu)

testing/baselines/TestOBJUnlit.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:48187bfef8e71b74c376879f6787c0eb611a839fc90c5f593ed17bbe61a47920
+size 100

testing/data/cube_unlit.mtl

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:bf212ee2dd625ab64bf8f00211bbf4dee54e184de335247742d918556bbc1a33
+size 674

testing/data/cube_unlit.obj

@@ -340,36 +340,41 @@ bool vtkF3DMetaImporter::Update()
 
       // convert to PBR materials if needed
       // this should be moved elsewhere, see https://github.com/f3d-app/f3d/issues/2995
-      if (!genericImporter && actor->GetProperty()->GetInterpolation() != VTK_PBR &&
-        actor->GetProperty()->GetLighting())
+      if (!genericImporter && actor->GetProperty()->GetInterpolation() != VTK_PBR)
       {
-        actor->GetProperty()->SetInterpolationToPBR();
-
-        // Convert to linear space
-        auto toLinear = [](double c) { return std::pow(c, 2.2); };
-        double diffuseColor[3];
-        actor->GetProperty()->GetColor(diffuseColor);
-        actor->GetProperty()->SetColor(
-          toLinear(diffuseColor[0]), toLinear(diffuseColor[1]), toLinear(diffuseColor[2]));
-
-        // restore diffuse/specular to 1 and ambient to 0
-        actor->GetProperty()->SetSpecular(1.0);
-        actor->GetProperty()->SetDiffuse(1.0);
-        actor->GetProperty()->SetAmbient(0.0);
-
-        // texture diffuse is now base color
+        // get texture
         vtkSmartPointer<vtkTexture> diffuseTex = actor->GetTexture();
         if (!diffuseTex)
         {
           diffuseTex = actor->GetProperty()->GetTexture("diffuseTex");
         }
         if (diffuseTex)
         {
-          actor->SetTexture(nullptr);
           diffuseTex->UseSRGBColorSpaceOn();
+        }
+
+        if (actor->GetProperty()->GetLighting())
+        {
+          actor->GetProperty()->SetInterpolationToPBR();
+
+          // Convert to linear space
+          auto toLinear = [](double c) { return std::pow(c, 2.2); };
+          double diffuseColor[3];
+          actor->GetProperty()->GetColor(diffuseColor);
+          actor->GetProperty()->SetColor(
+            toLinear(diffuseColor[0]), toLinear(diffuseColor[1]), toLinear(diffuseColor[2]));
+
+          // restore diffuse/specular to 1 and ambient to 0
+          actor->GetProperty()->SetSpecular(1.0);
+          actor->GetProperty()->SetDiffuse(1.0);
+          actor->GetProperty()->SetAmbient(0.0);
 
-          actor->GetProperty()->SetColor(1.0, 1.0, 1.0);
-          actor->GetProperty()->SetBaseColorTexture(diffuseTex);
+          if (diffuseTex)
+          {
+            actor->SetTexture(nullptr);
+            actor->GetProperty()->SetColor(1.0, 1.0, 1.0);
+            actor->GetProperty()->SetBaseColorTexture(diffuseTex);
+          }
         }
       }