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I have a question regarding the "new" scaling method with the latest version of 3.3. I initially learned scaling on OpenSim 3.2 where you would move the pink/virtual markers to reduce the max and RMS error between the virtual and experimental markers. I understand now that in the 3.3 version, the virtual markers are matched (put exactly in same position) with their corresponding experimental markers. Therefore, the step in version 3.2 where we clicked preview markers before movement is eliminated,as the virtual markers are moved to correspond exactly to the position of the experimental markers. We still get the RMS and max error for marker placement in the message window. I therefore understand that in order to get a smaller error in this 3.3 version, we would need to try and change the scaling factors of the different segments only, as opposed to moving the location of the virtual markers to match the location of the experimental markers, is that correct?

I was looking on the forum for an answer to this question and found this related topic: https://simtk.org/forums/viewtopic.php?f=91&t=5836. However, it didn't explicitly answer the question. I also tried to preview the experimental data, but the two sets of markers are not superimposed as it used to be in 3.2, and therefore makes it hard to compare both markersets (virtual and experimental).

Thank you very much for you help.

Erica-

There was no change in the Scale algorithm between 3.2 and 3.3. The 'Preview Static Pose' option in GUI was incorrect and was giving incorrect results. In the previous versions, it may have looked like the markers hadn't moved but they had. So there was a disconnect between what was presented on the screen and the actual changes to the model.

There is a previous forum post that gives some detail on the marker placer step here;
https://simtk.org/forums/viewtopic.php?f=91&t=4477

When comparing marker positions using experimental data, either the model or data has an offset imposed when loaded in the GUI. You can change the offset in the Navigator window.

Cheers,
-j