Hello,
I have generated what should be a valid 4OFF file, however trying to open it within stella gives a popup with the text; 'CreateCells failed: coplanar faces?'. Is there a way to view which cell stella failed on? A debug log or something similar?
Thanks
4OFF debug information
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robertw
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Re: 4OFF debug information
Hi, nope I'm afraid Stella won't give any further details. This error is happening when it's trying to group the faces into cells. You can optionally specify the cells too in the 4OFF which may help if there's any ambiguity.
Looking at the code, the error is given if either of two conditions fails. Been a while, so not entirely sure, but it seems one is finding coplanar faces sharing an edge, which it doesn't want to put into the same cell. The other is that it just doesn't find a neighbouring face to include in the cell. That's probably more likely. That is, the surface has holes in it.
If you send me the OFF file I may be able to see what's wrong with it. I'm interested to see what's triggering that error.
Looking at the code, the error is given if either of two conditions fails. Been a while, so not entirely sure, but it seems one is finding coplanar faces sharing an edge, which it doesn't want to put into the same cell. The other is that it just doesn't find a neighbouring face to include in the cell. That's probably more likely. That is, the surface has holes in it.
If you send me the OFF file I may be able to see what's wrong with it. I'm interested to see what's triggering that error.
Re: 4OFF debug information
I did specify the cells in the 4OFF, but it still gave the same error.
I'm trying to attach the file to this post, but it doesn't seem to accept any file extensions, I'll just email it to you.
I'm trying to attach the file to this post, but it doesn't seem to accept any file extensions, I'll just email it to you.
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robertw
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Re: 4OFF debug information
Hi, yep just emailing is the way.
Had a look at your file. First, when specifying the cell, you still need to include the number of edges on the second line, which can be zero because it's ignored, but since 4OFF expands on the original OFF format, the edge-count still has to be there. So first two lines should be:
4OFF
21 108 0 48
But I see the main issue. Your vertices all have zero in the 4th column, ie they're 3D coordinates not 4D.
Had a look at your file. First, when specifying the cell, you still need to include the number of edges on the second line, which can be zero because it's ignored, but since 4OFF expands on the original OFF format, the edge-count still has to be there. So first two lines should be:
4OFF
21 108 0 48
But I see the main issue. Your vertices all have zero in the 4th column, ie they're 3D coordinates not 4D.
Re: 4OFF debug information
Ah well that was embarrassing, but I appreciate the help.
The file I sent you was actually incorrect; I don't know why the 'w' coordinates had been zeroed, but the file I meant to send has the proper coordinates. However, adding the number of edges did fix my issue and Stella was able to move forward.
The issue I am having now would be stella reporting the polytope not being closed... which is odd because the method I use to create them is a grown mix of an FCC and BCC lattice type structure. It works fine in 3 dimensions, but I am trying to use stella as a visualizer to see what is produced by adding the fourth due to my lack of geometric / mathematical experience, and unfortunately it's not adding up.
The file I sent you was actually incorrect; I don't know why the 'w' coordinates had been zeroed, but the file I meant to send has the proper coordinates. However, adding the number of edges did fix my issue and Stella was able to move forward.
The issue I am having now would be stella reporting the polytope not being closed... which is odd because the method I use to create them is a grown mix of an FCC and BCC lattice type structure. It works fine in 3 dimensions, but I am trying to use stella as a visualizer to see what is produced by adding the fourth due to my lack of geometric / mathematical experience, and unfortunately it's not adding up.
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robertw
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Re: 4OFF debug information
Sorry for slow reply. Feel free to send me another OFF file if you want. But Stella works best with polytopes. In 3D it expects exactly 2 faces to meet at each edge, whereas a 3D lattice may have any number of faces meeting at an edge. A lattice doesn't generally have a surface as such, depending how you do it.
Same in 4D, it expects exactly two cells to meet at each face. But I'd have to see what you're doing.
Same in 4D, it expects exactly two cells to meet at each face. But I'd have to see what you're doing.