Measurement Tools

Anne Jorstad edited this page Jul 1, 2018 · 13 revisions

This module measures surface areas, volumes, and lengths of regions of meshes specified by a user-defined selection of vertices. New objects are created as children of the original mesh object, and the measurements are stored in appropriate property variables of these children objects in the Geometry Properties panel of the Object context (bottom right of the Blender interface, see below for details). Measurements can be exported into a .csv file that can be read by Excel.


Surface Area and Volume Measurements

  • Select the mesh object to be measured and enter Edit Mode by clicking tab on the keyboard.

  • Select the vertices of the subregion to be measured. This can be done using the lasso select (shortcut: ctrl - left click) to drag the mouse to form a freehand selection area. Non-visible vertices can be selected by disabling the "limit selection to visible" option in Blender at the bottom of the Blender interface in Edit Mode). Vertices can be deselected by hitting the a key.


  • Click on either the Surface Area or the Volume button. Make sure to give a name to the feature measured, eg. "spine1".
    • Surface Area: Measures the surface area of the continuous region defined by the currently selected vertices. Creates a new mesh object as a child of the active object called "name"_surf that consists of exactly those vertices selected.
    • Volume: Measures the volume of the continuous regions defined by the current selected vertices. Creates a new mesh object as a child of the active object called "name"_vol that consists of the selected vertices, and in addition, any additional vertices that are required to close any open holes of the selected region, as volume can only be defined on a closed mesh. Provides both volume and surface area measurements, where the surface area includes the areas of the triangles required to close any open holes, so may be larger than the surface area found from the "Surface Area" button.

  • Both: Calls both Surface Area and Volume.

  • Multi Object: Measures both surface area and volume of all selected objects. This button is useful for measuring many small closed objects at once, and only the "name"_vol objects (which contain both surface area and volume measurements) are created.

  • The measured feature will be a child of the original object, and will be hidden (to make visible, click on the eye icon). It will be listed in the "Outliner" window on the right.

  • The measured values are displayed in the "Geometry Properties" panel of the "Object" context in the Properties window (bottom right of the Blender interface).


Length Measurements

All length measurements calculated will be displayed directly in the panel.

Uncheck "Create Length Object" if you do not want to create a child object of edges used in the length calculation.

  • Distance Between 2 Points: Length of line segment connecting two points in space (select two vertices, the click). Child object will be called "name"_dist_3D_seg. Example of two such segments seen here.

  • Shortest Distance on Mesh: Shortest path between two points through vertices on the mesh (select two vertices, the click). Child object will be called "name"_dist_on_mesh.

  • Length of Selected Edges: Total distance of all selected edges (select all desired edges or points to include, then click). Child object will be called "name"_dist_edges.

Scale

  • Apply Scale: Rescales all objects and child objects by the scale factor defined by "scale".

Output Data

  • Export Measurements: Exports all scene measurements to the user-defined file by listing all object information with column format "Object Name,Parent,Surface Area,Volume,Number of Vertices,Length,Path" into a .csv file that can be read by Excel.

  • Export Selected: Exports the measurements of only the selected objects and their children.

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