Skip to end of metadata
Go to start of metadata

This morning we'll work with anatomical coordinate systems (ACSs) and joint coordinate systems (JCSs) for measuring motion

1) Create a standard (from Brainerd et al. 2010) JCS for pig TMJ

Select a specific frame of your pig animation in which the jaw is closed and centered. This "pose" will be the zero position = "reference pose" for your JCS.

  • Create a polygon plane: top menu Create/Polygon Primitves/Plane/. Scale the plane X to 10 cm and Z to 7 cm. If you have interactive creation on, then top menu Create/Polygon Primitves/Plane/ and drag on the grid to create a 10 x 7 cm plane.
  • Translate and rotate the plane to align it with the occlusal (chewing) surface of the lower jaw teeth. 
  • Translate the plane along the Y axis to intersect the pointy medial tips of the mandibular condyles.
  • Press Jax button to create anatomical coordinate system (ACS) for pig mandible. Do not press “Set Joint Axes” yet. And do not close the jAx window.
  • A "giant locator" will be created at the origin. Rotate and translate (by hand) the giant locator to the plane.
  • Align the blue (Z) axis to go through the medial tips of the mandibular condyles, with arrow pointing toward the pig's right side. Red (X) and green (Y) as in image below.

  • Select File/Save As and save the file with JCS2 (joint coordinate system 2) in the file name. Then Select File/Save As and save the file again with JCS1 in the file name.
  • Then press “Set Joint Axes” (on your JCS1). Play the animation.
  • Select yourJointAxesdata object in the Hypergraph Hierarchy (top menu: Window/Hypergraph Hierarchy)

2) Create a 45 degree rotated JCS (Optional, if time)

  • Save the JCS1 file and open your JCS2 file. Rotate the axis system about 45 degrees around the Z-axis (so now the X and Y axes are no longer pointing in the rostro-caudal and dorso-ventral directions).
  • Click jAx if you do not see the Anatomical Joint Axes window. Click Set Joint Axes.
  • Look at 6 DOF rigid body graphs in Maya; Export 6 DOF data; compare with JCS1 in Excel (or preferred graphing program)
  • Try other JCS locations and orientations. Can you place the JCS in a location that reduces Z-translations?

3) Measure mouth opening and closing (gape) distance (TOOL IS CURRENTLY BROKEN, SO NEVER MIND)

  • Measure gape between the upper and lower incisors.
  • Wiki Link: Instructions for measuring and importing distances between two points. 
  • Measure distance using the distance tool (Create/Measure Tools/Distance Tool). 
  • Select the distance tool, then click and drag in the Maya scene. This will create two locators. Move these locators to the two positions on your mesh models that you want to measure between.
  • Hint: hold down "V" while moving the locator to snap the locator to the mesh model. Caution: this sometimes snaps the locator to an interior surface.
  • Parent point 1 to bone 1 (upper incisor locator to skull) and point 2 to bone 2 (lower incisor locator to mandible). 
  • Export distances by selecting the DistanceDimension(transform) from your hypergraph. Use the EXP button on the XROMM Toolbar, select distance as the data type.

4) Measure gape as dorsoventral (DV) position relative to an Anatomical Coordinate System of the skull, oriented to the anatomical directions (dorsoventral, mediolateral and rostrocaudal). (TOOL IS CURRENTLY BROKEN, SO NEVER MIND)

  • No labels