Display Particle Paths

This option determines the form of diagnostics displayed during the tracking process. The diagnostics will be displayed using the second extended memory buffer and buffer 0, when the latter is not in use for other purposes.

When not using buffer 0, display: particles on Location, Matching or Validation, or display Nothing?

<L> will cause a white dot to be added to the display for each particle as it is located; particles which were located in the previous frames are displayed with lower intensities. <M> will display the particle positions only after a matching has been made and <V> only after a matching both forwards and backwards in time. Displaying <N>othing is inadvisable as it is more difficult to determine if the tracking is behaving properly.

<M> will cause a white dot or line to be added to the display for each particle for which a match is found. If the location of the particle at the previous time step is not already displayed, then it will also be added.

<V> will cause the particles to be plotted only once they have been matched at least twice (ie. the path extends over at least three frames). Note that the position of the particle at the first frame on the path will not be shown.

<C> produces a graphical version of the cost matrix used in the modified transportation algorithm (see the help facility within the [P Pricing policy] menu for more details). Each row of this matrix corresponds to a particle at the old time step, and each column to a particle at the new time step. The costs are scaled from 0 to 254, with 255 (white) reserved as infinite costs, representing prohibited matchings.

<B> displays both the particles on matching and the cost matrix at different times during the tracking process.

<N> prevents any diagnostic display from being produced. This option allows more rapid execution, but in general the diagnostics from <M> are considered worth the computational overhead.

Decrease intensity by how much for each sample ?asdf

Prior to displaying new particles, either on location or at matching, the image containing the particles so displayed during the previous time step is decreased in intensity by the amount specified by this entry. Thus we are able to build up a picture of the evolution of the flow with the most recent particle locations displayed in white, and the history of their paths slowly fading into the background.

Plot Points or Lines ?

When either <M>, <V> or <B> has been chosen, the particle positions are ploted after a matching has been found. This plotting may be either in the form of single pixels (<P>), or lines (<L>) connecting the old and new locations. Note that the lines option will only be of use when the particles move a relatively large distance between time steps, and that the execution of this is significantly slower than the single pixel approach.

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DigImage User Documentation

Stuart Dalziel, last page update: 19 February 1996