Shading error

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Old 06 June 2005   #1
Shading error

Ok this is driving me crasy. I have made this extremely basic set in silo.
It is just a bunch of cubes. I exported it to maya and this is the way it looks in viewport and during render. It is just a simple lambert shader.

I exported it as a obj it is pretty large in scale 150m wide I believe. I know it would be just as easy to just do this right in maya. These are !@#$% cubes. But my bigger concern is what is causing this at all. I tried to adjust the normal soft/hardness in maya an nothing changed, so I am out of ideas. Is this due to the size? Am I missing an export setting in silo?

All clues to solve this would be much appreciated.

Old 06 June 2005   #2
are all the poly normals facing the same way (edit: heh, I mean all facing outward)?

Can you upload the object somewhere so we can have a look at it?

Last edited by Cinnsealach : 06 June 2005 at 09:41 AM.
Old 06 June 2005   #3
Here is a link to the file. Again in silo all is well it is when exported to maya/xsi that this error occurs.

File here right click save as. It is a simple obj file. I also tried this with a unedited cube default size position everything, same problem. I wonder if it is a obj error possibly maya/xsi interpret the file differently than silo. I have exported other objects without this issue, they were not as basic and often subdivided in render app.

Thanks for the help,

Old 06 June 2005   #4
I found the problem but not the best fix. I opened up the object in xsi, and there is a user normal cluster assigned. deleting this solves the problem. Now I need to know how to make silo not create this in the first place. Any ideas? I am a totally maya noob and do not know where this might be hidden in that app.... really do not like the idea of having to run everything through xsi before bringing it into maya.
Old 06 June 2005   #5
First, what exactly are you seeing in Maya that you aren't expecting? What looks wrong to you? Everything looks like it should as far as I can tell.

Second, the User Normal Cluster you are seeing in XSI is something that XSI adds on to OBJ files it imports, because this is not something that is supported in an OBJ file.

If you tell me what you think is wrong I can try and help you fix it.
mike hovland
lead technical artist

Life beats down and crushes the soul... art reminds you that you have one. - Stella Adler
Old 06 June 2005   #6
Ok well the thing is when this user normal cluster is removed the diagonal shading you see in the image is no longer present. It is in renders as well as open gl view. This is not present in silo, only when imported to either maya or xsi. Now when the object has this user normal stripped it causes maya to render with a warning for each object, but the render looks fine.

// Warning: (Mayatomr.Scene) : object1Shape: empty UV set map1 detected, ignored //

I can live with it in this scene, but with advanced object this will be a big problem. Could there be a export setting in silo i am missing? The images below have the same lighting and shaders.

this is a render without the removed clusters.

this is with the cluster removed.

Old 06 June 2005   #7
Can you post the Maya scene file, so I can look at it?

What version of Maya are you using?
mike hovland
lead technical artist

Life beats down and crushes the soul... art reminds you that you have one. - Stella Adler
Old 06 June 2005   #8
opengl error

maya error

Ok I posted two files one that is just the imported obj file with the visual error. The second is of the error about the uv maps after stripping out the cluster in xsi. I am using maya 6.5, and xsi 4.2, and silo 1.4. I am pretty new to both maya and silo. Just started using maya about 3 months ago and do only animation in it. Really do not know my way around in it to well. Silo I have only been using for about 6 weeks I guess. Thanks so much for your help Mike much appreciated.
Old 06 June 2005   #9
I fixed the openGL problem. Here is how to go about it.

select all the objects and go to:

Edit Polygons => Normals => Set Vertex Normal => Option Box

Now go to the Edit menu at the top of the window, and Reset Settings, click Apply.

That will fix the problem. If you want to see what is going on, instead of selecting all the objects, do the fix on one of the objects, and then select:

Edit Polygons => Normals => Vertex Normal Edit Tool => Option Box

If you look at the vertex normals that are displayed on the fixed object, you will see that at the corner of each box, you have 3 normals pointing out.

Now select one of the boxes that isn't fixed, and you will see only 1 normal pointing out, at the average of the vert normals. You also see a big manipulator. If you rotate the manip, you will be moving the normals for the average of the verts. Move the manip, and then undo it, and you will see all 3 normals pop out.

Does that solve the problem?

Why this is happening is because the OBJ format isn't writing out per vertex normals, and is averaging out the face normals to arrive at the vertex normal. You have both face normals (which determine which direction the face is pointing) and vertex normals (that define shading across edges). Here is the information for the first objects vertices, and the vertex normals:

v -522.197 -10.4401 -720.084
vn -0.57735 -0.57735 -0.57735
v 749.705 -10.4401 -720.084
vn 0.57735 -0.57735 -0.57735
v -522.197 -0.44009 -720.084
vn -0.57735 0.57735 -0.57735
v 749.705 -0.44009 -720.084
vn 0.57735 0.57735 -0.57735
v -522.197 -10.4401 595.62
vn -0.57735 -0.57735 0.57735
v 749.705 -10.4401 595.62
vn 0.57735 -0.57735 0.57735
v -522.197 -0.44009 595.62
vn -0.57735 0.57735 0.57735
v 749.705 -0.44009 595.62
vn 0.57735 0.57735 0.57735

Notice that the vn (vertex normal) lines are all the same (well almost the same, they are the same 0.57735 values, some positive, some negative, either way, it is an average).

Hope that helps with that issue.

The second issue is that OBJ's from Silo don't export UV's, really. If you open the OBJ file in a text editor, you will see this in the face list:

f 4/1/4 2/2/2 1/3/1 3/4/3
vt 0 0
vt 0 0
vt 0 0
vt 0 0

The f (face) line defines the face, and the vt (vertex texture) lines are for UV information for the face, which are all set to 0's.

To get around this, in Maya just apply some sort of UV mapping to the objects, and the errors go away.
mike hovland
lead technical artist

Life beats down and crushes the soul... art reminds you that you have one. - Stella Adler
Old 07 July 2005   #10

Awesome! Thanks so much for sorting this out for me, I am really very grateful! Thought I was losing my mind there.... You went way out of your way to help. Thank you so much for that!
Old 07 July 2005   #11
Anytime! Glad I could help. If I can answer anymore Silo / Maya questions for you, let me know.
mike hovland
lead technical artist

Life beats down and crushes the soul... art reminds you that you have one. - Stella Adler
Old 07 July 2005   #12
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