OpenGL tinkering

# 1 12-04-2010 , 01:03 AM

Level 32 pachyderm
Join Date: Dec 2007

Location: England

Posts: 1,859

I've been experimenting with openGL (using pyOpenGL for python)
So far I've managed to get a textured cube to rotate. I've got my code and a screen shot attached in the zip file. As you can see on the screenshot, there are strange things going on at the edges of the cubes. Does anyone know of a likely cause/solution?

Next I'm going to try to display an .obj file.

Attached Files

archive.zip (152.4 KB, 288 views)

https://users.ecs.soton.ac.uk/as28g11/

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# 2 13-04-2010 , 06:33 PM

Level 32 pachyderm
Join Date: Dec 2007

Location: England

Posts: 1,859

I've finished my class to load and display .obj files. It works on some models but doesn't work on anything I export and I get a rather strange error:

Code:

Traceback (most recent call last):
  File "/Users/Elephant_Inc/Desktop/bpwpapcode/Chapter11/tankdemo.py", line 92, in <module>
    run()
  File "/Users/Elephant_Inc/Desktop/bpwpapcode/Chapter11/tankdemo.py", line 64, in run
    tank_model.read_obj('elephanilla.obj')
  File "/Users/Elephant_Inc/Desktop/bpwpapcode/Chapter11/model3d.py", line 120, in read_obj
    texture_path = os.path.join(model_path, material.texture_fname)
  File "/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/posixpath.py", line 60, in join
    if b.startswith('/'):
AttributeError: 'NoneType' object has no attribute 'startswith'

I've triangulated the mesh (I have a thing in the program to check for that anyway). Does anyone know what the cause could be?

https://users.ecs.soton.ac.uk/as28g11/

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# 3 14-04-2010 , 12:11 AM

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Location: Michigan, USA

Posts: 2,998

well from the traceback it appears things start to go south starting at line 60 and the error does not seem to be with the .obj file at that point but with hashing the path "/" character.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 4 14-04-2010 , 12:55 AM

EduSciVis-er
Join Date: Dec 2005

Location: Toronto

Posts: 3,374

Well it's not necessarily the / character itself, but that you've got a NoneType (essentially nothing) when it's expecting a string or something like that. Basically I don't think the .obj is getting passed in correctly, but I think you already knew that. Could you try with a simple cube or something?

-stwert

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# 5 14-04-2010 , 10:03 AM

Level 32 pachyderm
Join Date: Dec 2007

Location: England

Posts: 1,859

I tried it with a cube and got the same error, but I tried it with someone else's model and it did work. I wonder if Maya does something my program doesn't like.
I'll go back to the cube and see if I can find anything strange in there.

Code:

texture_path = os.path.join(model_path, material.texture_fname)

This seems to be the problem with my program. Maybe it doesn't like the fact that it has no texture.

edit: :attn:
I've got it to work. It didn't like the fact that no texture was specified.
Thanks for the help.
user added image

https://users.ecs.soton.ac.uk/as28g11/

Last edited by elephantinc; 14-04-2010 at 11:59 AM.

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# 6 14-04-2010 , 04:14 PM

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Join Date: Dec 2007

Location: England

Posts: 1,859

Here's my elephanilla model rendered using my program:
As you can see, all the duplicated features (eyes, tusks etc.) don't seem to display properly. So far I've had no luck figuring out what's causing it.
It seems that the half facing away from the camera (that shouldn't be drawn) is being draw but the half that is facing the camera isn't being.

After a bit of testing, it seems to happen when I duplicate/mirror the features. If I duplicate with out mirroring them, they display fine.
Reversing the normals seems to fix it but messes up the lighting

edit: After freezing transformation and reversing normals, it displays correctly! Now I'm going to add some camera controls and then I'll try and make it a bit less picky.

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