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**UNDER CONSTRUCTION**


Measuring XYZ Coordinates of a Point Over Time in an Anatomical Coordinate System

Sometimes it is valuable to track (over time) the XYZ coordinates of a single point relative to a user-defined anatomical coordinate system. This is useful, for example, if soft tissue markers have been implanted and their movement relative to a coordinate system defined by the bones is of interest.

  1. Press the gLoc button in Maya XROMM Tools to create a Giant Locator
  2. Move and rotate the Giant Locator into position to define the Anatomical Coordinate System (ACS)
  3. Parent the giant_locator to the reference object (usually a bone)
  4. Create a regular locator for the point you want to track. Move it to the position you want to track (holding down the V key while moving the locator will snap it to the nearest point on a mesh).
  5. Parent regular locator to the animated movement of interest (usually either a bone or an animated locator)
  6. Press the oRel button in Maya XROMM Tools to output Relative Motion
  •  In the pop-up window, specify the proximal object: the Giant Locator
  • distal object: the regular locator or some other point whose motion you want to measure
  • output node: name of the data node

5. Press Output relative data. This should give you a data node (locator) with the motions of the point calculated relative to the coordinate system.

6. You can then view the data in the Graph window and export the relative motion data using the exp shelf tool.

 

Older Method:

  1. Type createGiantLocator("giant_locator") in the Mel box (replace giant_locator with the name of the coordinate system that you wish to create; the quotation marks are necessary)
  2. Move and rotate the giantlocator into position to define the anatomical axis
  3. Parent the giant_locator to the reference object (usually a bone)
  4. Create locator1 (topMenu/Create/Locator)
  5. Move locator1 to point of interest
  6. Parent locator1 to the animated movement of interest (either a bone or an animated locator)
  7. Create a second locator by duplicating the first locator (control + d) – the second locator should be in the same location as the first
  8. Move to frame with preferred zero position for locators
  9. Parent locator2 to giant_locator
  10. (optional step) Set Zero
    • select locator 2
    • freeze transforms/translations to set xyz zero position
  11. Constrain locator2 to locator1
    • select locator1 then shift-select locator2
    • topMenu/Constrain/Point (locator1 was already animated by parenting it to movement of interest; now locator2 will be constrained to move with locator1, but its movement will be defined in the giant_locator coordinate system)
  12. Export translations of locator2
    • select locator2
    • select the names (attributes) Translate X, Translate Y, Translate Z in Channel Box
    • type exportSelAttr in MEL box (need old exportSelAttr script for this)
    • Note: the following should work, but is not working with XROMM Maya Tools 2.1.4
    • press exp button on XROMM Maya Tools Shelf
    • select translation, global coordinate system
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