Statistics Menu

This menu has a number of options for performing statistical and related operations.

Average construction

Match to base face

This is a legacy function used to align surface via delineation of the 2D texture map using a .tem file. Recommended to use the warping options on the Edit menu instead.

Display N

Displays the number of faces in this averge on the status line (at the bottom of the window).

Add to average

Prompts for a .obj file to add to the currently displayed (average) surface. Files should have the same mesh structure before calling this method, use Edit->Warp3D.

Average list

Average a set of .obj files together. The list is read from a text file with the name of each (aligned) .obj file on each line.

Iterate average

Tick this option when averaging lists of faces for improved accuracy of the average. The shape of the average is affected by the (rigid+scale) alignment of the faces, for best results faces to be averaged should be aligned to the average. As the average is initially unknown this iterates by aligning to the current estimate of the average each iteration.

Auto procrustes normalise

Procrustes normalisation is rigid body plus scaling to minimise the differences between surfaces. This option should be turned on unless the surface position/orientation/scale are pre-normalised some how.

Using averages

For all the following operations all files must have the same mesh structure (ie. number of vertices). It is best to warp a standard shape into all the files you want to use using the Batch Warp method before constructing the averages, comparing and transforming.

Compare individual

Compare a single subject to an average. You should have the subject loaded and you are prompted for the average. The results show the Manhalobis distance of each point from the average as a colour i.e. the distance scaled by the shape of the distribution.

Compare averages

Compare two averages using Hotelling's T^{2 test at each vertex (related to the Student's t-test for 1D distributions). Shows the facial areas where the samples are significantly different.}

Transform

Adds the differences between two surfaces (usually averages) to alter a facial surface. You are prompted for the two (average) surfaces and the amount to scale the differences by. e.g. to change a female face to their male equivalent load the subject's (standard) mesh, select Transform, load the female then the male average when prompted, then set the change to 1 (100% of the difference between the two).

View Morph: Loads a sequence of (aligned) faces over time. The text file should have the name of the file to use and the time point of each on each line. The times should be ordered in increasing value starting at 0 e.g.

face0.obj 0
face1.obj 10
face2.obj 40
face3.obj 45
face4.obj 60

A dialog will be displayed allowing the morph frame to be selected or the sequence animated (using the play button).

Shape PCA