Normals/roughness appear to be missing from display using vtkOBJImporter

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1

Hello,

I’m using vtkOBJImporter to display an obj file. I have an associated .mtl file which references various roughness, normals, diffuse texture .pngs etc.

VTK succesfully displays the .obj file and I can clearly see the contents of the diffuse texture are included but it seems like the normals and roughness are not being processed - the image is completely flat.

I’m using Python and VTK 9.2.2 on Windows and the code I’m using is shown below.

Any ideas on why the normals/roughness are not being processed?

Thanks in advance,

Doug

def main():

    # Get the full pathname of the vtp file containing the cow definition from the res folder
    current_file_path = os.path.dirname(os.path.realpath(__file__))

    objfname=os.path.join(os.path.dirname(current_file_path), r'res\snowman\snowman_finish.obj')
    matfname=os.path.join(os.path.dirname(current_file_path), r'res\snowman\snowman_finish.mtl')
    texturepath=os.path.join(os.path.dirname(current_file_path), r"res\snowman")

    # Set up the importer and initialize with the files
    objimporter=vtkOBJImporter()
    objimporter.SetFileName(objfname)
    objimporter.SetFileNameMTL(matfname)
    objimporter.SetTexturePath(texturepath)

    # Render window, renderer and interactor
    renderer=vtkRenderer() 
    renwin=vtkRenderWindow()
    renwin.AddRenderer(renderer)
    iren = vtkRenderWindowInteractor()
    iren.SetRenderWindow(renwin)

    # Connect the importer to the render window
    objimporter.SetRenderWindow(renwin)
    objimporter.Update()

    # Render
    iren.Initialize()
    renwin.Render()
    iren.Start()


if __name__=='__main__':
    main()
1 Like
2

Here’s what the display looks like in VTK

Flat snowman
Flat snowman562×583 36.5 KB

And how it looks in an alternate viewer

image
image926×766 23.6 KB

3

mtl file

newmtl snow
Ns 225.000000
Ka 1.000000 1.000000 1.000000
Kd 0.800000 0.800000 0.800000
Ks 0.500000 0.500000 0.500000
Ke 0.000000 0.000000 0.000000
Ni 1.450000
d 1.000000
illum 2
map_Bump -bm 0.500000 snowman2_normal.png
map_Kd snowman2_diffuse.png
map_Ns snowman2_roughness.png

newmtl snowman1.001
Ns 225.000000
Ka 1.000000 1.000000 1.000000
Kd 0.800000 0.800000 0.800000
Ks 0.500000 0.500000 0.500000
Ke 0.000000 0.000000 0.000000
Ni 1.450000
d 1.000000
illum 2
map_Bump -bm 0.500000 snowman1_normal.png
map_Kd snowman1_diffuse.png
map_Ns snowman1_roughness.png
4

OK - After some more research, I found,

  1. vtkOBJImporter is known to support only a single texture. Not sure how I missed that i my initial research
  2. Even if it supported multiple textures my current approach would not have worked because the default Gouraud shading model only supports a single color texture. I need to update my code to use PBR rendering to see the effects of the different roughness etc, textures.
2 Likes