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Measure CT Marker Coordinates in Maya

What you need:
Mesh models of your radio-opaque markers in .obj format
Mesh models of your bones in .obj format

What you get:
A .csv file containing the xyz coordinates of your markers in CT space

In this step, 3D models of the bones and their markers will be imported into Maya. Then the XYZ coordinates of the markers, relative to the polygonal models of the bones, will be measured and saved as CTmarkerCoordinates. This step is done in Maya using the XROMM Maya Tools&nbsp

1)  Import bone and marker models

  • In Maya, go to file<import
  • Make sure the file type is set to .obj, .ma or BestGuess click here if you have VRML models.
  • select the file and click ok
  • repeat for each model

(Note: Depending on what method you used to get the bone models, the bone models can be in a different scale than the Maya scene. That results in animations were bones are misaligned or overlapping. One way to check that is to create the mayacams as for Rotoscoping and rotoscope one frame for one bone. Another way is to check scale against the grid.)

2)  Get marker coordinates from the marker models

  • In the main camera view window, select all bone models (but not the markers). Hit ctrl+h on the keyboard to hide all of the bones. Only the markers are showing. OR use Layers to hide and show objects (preferred).
  • Select the marker object
  • right click and select vertex from the marking menu
  • drag select the vertices for a single marker
  • click vAvg on the XROMM tool shelf or type vertAvg on the command line.
    If you are using XROMM_Maya_tools_2.0.6 or later, the window will look like this:

    This window will name markers one at a time rather than creating a list of markers for you to choose from. This change was made to make the vertAvg tool work better on Mac computers. If you are a PC user and prefer using the old window (below), replace the vertAvg script in your scripts folder with one from an earlier version of XROMM_Maya_tools.
  • In the Marker Name box, enter a name that you want all of the markers to have. You can leave this with just the "m" if you would like. If you just have the "m", then the locators will be named m_001 etc.
  • With the markers in vertex mode, select all of the vertices of the marker you want to create a locator for.
  • In the Marker Number window, enter the number of the marker you want to create a locator for.
  • Press the Calculate Centroid button and a locator will be created.
  • Repeat this process for all of your makers.

3)  Export the CT marker locator data

  • Click the CTex from the XROMMtools Shelf, or type CTMexport in the MEL box
  • Select all of your marker names
  • Save the .csv file

If you are using XROMM_Maya_tools_2.0.5 or earlier, the window will look like this: 

  • Type in the number of markers you have and press enter. In the above example, we had 10 markers.
  • Select the marker number from the list that corresponds to the vertices you selected and hit the "calculate centroid" button.
  • A locator is created with the xyz coordinates of the marker centroid. It will be name "marker##" where ## is the number you typed.
  • repeat for all markers
  • (hint: if you need to see the bones to determine marker numbers Shift+h will unhide the bones)
  1. Export the CT marker locator data
    • This step can be done in the vAvg window if you are using the older version. Once you have created centroid locators for all of the makers, the "export centroids" button will become black. Press this button and save the file it produces.
    • If you closed the vAvg window, you can also export the marker locations by doing the following:
      • select all of the locators that you just created.
      • click the CTex from the XROMMtools Shelf, or type CTMexport in the MEL box
      • Save the .csv file
    • Save the scene.

Converting .wrl (VRML) models into Maya-friendly format (Windows only). Note: it is more convenient to export 3D models in .obj format from Amira (or Microscan Tools) because .obj files can be imported directly into Maya. These instructions are provided in case only VRML models are available.

If using older SmoothData MATLAB script, then Reset Bone element pivots(**this step omitted if using rigidBody MATLAB script)

  1. Select all marker locators for single bone (using shift select for multiple selection)
  2. Shift select the bone associated with the selected locators
  3. click the mvPv button on the XROMMtools shelf
  4. repeat for each bone
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