Deciphering a coordinate system in an XML file

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Discussion Overview

The discussion revolves around understanding a coordinate system used in an XML file containing image data, specifically focusing on the representation of points and triangles in a 3D space. Participants are exploring the structure of the XML data, its potential relation to the DICOM format, and how to effectively plot the data.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the XML contains two sets of image data represented in x, y, z coordinates, and mentions a specific structure for triangles that may be relevant.
  • Another participant suggests that the points might be grouped to form triangles, proposing a format for the coordinates based on the triangle's corners.
  • Some participants request additional information, specifically the XML header or references to a DTD or XSD, to better understand the structure and validate assumptions about the data.
  • There is mention of an inconsistency in the number of compared to , with one participant observing that some segments have double the number of indices.
  • One participant speculates that the backslash delimitation may be part of the DICOM format syntax, indicating a potential area for further investigation.

Areas of Agreement / Disagreement

Participants have not reached a consensus on the interpretation of the coordinate system or the implications of the XML structure. Multiple viewpoints and suggestions are present, indicating ongoing exploration and uncertainty.

Contextual Notes

Participants have not provided a complete view of the XML structure, particularly the header or any associated DTD/XSD, which may limit the understanding of the data format and its implications.

neu
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Hello, firstly I have to make the usual apologies of ignorance and inexperience, but that's why I'm here!

I have a library of XML files which each contain two sets of image data. Together they make something very similar to this:http://imgur.com/vjs7MRH

The grey and red points are given in basic x,y,z coordinates, the white line picture is given in less obvious coordinate system which is shown below.

XML:
<part>
<skin>
- <triangles>
- <segment name="Step_0">
  <positions>-3\0\0\-2\0\0\-2.7029\-1.3017\0\-1.8705\-2.3455\0\-1.8019\-0.8678\0\-1.247\-1.5637\0\-0.445\-1.9499\0\-0.6676\-2.9248\0\0.6676\-2.9248\0\-1.247\1.5637\0\-2.7029\1.3017\0\-1.8705\2.3455\0\-1.8019\0.8678\0\-0.445\1.9499\0\0.445\1.9499\0\-0.6676\2.9248\0\1.8705\-2.3455\0\0.445\-1.9499\0\1.247\-1.5637\0\1.8019\-0.8678\0\2.7029\-1.3017\0\2\0\0\3\0\0\0.6676\2.9248\0\1.247\1.5637\0\1.8705\2.3455\0\1.8019\0.8678\0\2.7029\1.3017\0\2.7029\1.3017\152.5\0.6676\2.9248\152.5\1.8705\2.3455\152.5\3\0\152.5\-1.8705\2.3455\152.5\-3\0\152.5\-2.7029\1.3017\152.5\-0.6676\2.9248\152.5\-2.7029\-1.3017\152.5\-0.6676\-2.9248\152.5\-1.8705\-2.3455\152.5\1.8705\-2.3455\152.5\2.7029\-1.3017\152.5\0.6676\-2.9248\152.5\-2\0\152.5\-1.8019\-0.8678\152.5\-0.445\-1.9499\152.5\-1.247\-1.5637\152.5\-1.247\1.5637\152.5\-1.8019\0.8678\152.5\-0.445\1.9499\152.5\0.445\1.9499\152.5\1.247\-1.5637\152.5\0.445\-1.9499\152.5\1.8019\-0.8678\152.5\2\0\152.5\1.247\1.5637\152.5\1.8019\0.8678\152.5</positions>
  <indices>0\1\2\3\2\4\5\6\7\8\7\6\5\3\4\7\3\5\4\2\1\9\10\11\1\0\12\12\0\10\9\11\13\14\13\15\13\11\15\12\10\9\16\17\18\6\17\8\8\17\16\18\19\20\19\21\22\22\20\19\16\18\20\23\24\14\25\24\23\15\23\14\26\27\21\22\21\27\26\25\27\24\25\26\22\27\28\25\23\29\27\25\30\28\31\22\29\30\25\28\27\30\23\15\29\15\11\32\10\0\33\11\10\34\32\35\15\33\34\10\32\11\34\15\35\29\0\2\36\3\7\37\2\3\38\36\33\0\37\38\3\36\2\38\7\8\37\8\16\39\20\22\31\16\20\40\39\41\8\31\40\20\39\16\40\8\41\37\36\42\33\43\36\38\37\44\45\44\37\41\43\38\45\45\38\37\42\36\43\32\34\46\47\33\42\34\33\47\48\32\46\35\48\49\35\32\48\46\34\47\50\51\39\41\51\44\39\51\41\40\52\50\31\53\52\52\40\31\40\50\39\49\54\29\29\54\30\49\29\35\53\28\55\28\53\31\28\30\55\55\30\54\12\47\42\13\48\46\9\46\47\42\1\12\46\9\13\9\47\12\13\49\48\24\54\49\21\53\55\26\55\54\49\14\24\55\26\21\26\54\24\13\14\49\19\52\53\17\51\50\18\50\52\53\21\19\50\18\17\18\52\19\17\44\51\5\45\44\1\42\43\4\43\45\44\6\5\43\4\1\4\45\5\17\6\44</indices>
  </segment>
[18 more segments]
</triangles>
</skin>
</part>

I've left out the rest of the code and other segments for brevity.

Interestingly, this segment had double the number of <indices> elements than <positions> elements, however other segments have less than double.

I have tried plotting this data in various ways to no avail.

I think the backslash delimitation is part of the DICOM format syntax.

Any help or suggestions of what this might be will be very much appreciated!.

Thanks
 
Last edited by a moderator:
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Since it says triangles then perhaps the points are grouped to make triangles:

1x/1y/1z/2x/2y/2z/3x/3y/3z where the 1,2,3 are the corners of the triangle and the 1x/1y/1z are the 3D coordinates of the 1st corner.
 
It would help if you showed the XML header (where they refer to a DTD - Document Type Definition).
 
Svein said:
It would help if you showed the XML header (where they refer to a DTD - Document Type Definition).
Or alternatively, an XSD - XML Schema Definition.
 

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