Change parameters such as Height, Age and Weight

[Akshay Desai]

Hello everyone,
Hope everyone is doing well. I have an OpenSim query. I am working on a project for Ergonomics and I would like to change the following parameters.
1. Height of my OpenSim model
2. Change in Age.
3. Change in Weight
4. Change in Speed.

Kindly reply as soon as possible, my project is getting delayed day by day, I am trying on this continously.

[Ayman Habib]

Hi Akshay,

While I agree that it would be a good idea to have generic models for these various demographics/Ages/genders, unfortunately we don't have such models. Typically our users collect motion capture data and scale the generic model to match the data. This would account for height, and possibly for mass but not the other factors.
There are studies that customize models for obesity or other factors but we don't have such models in house.

Best of luck.
-Ayman

[Akshay Desai]

Can you explain me the procedure for change in Height and Mass please?

[Karthick Ganesan]

Please see here for scaling the model.
https://simtk-confluence.stanford.edu:8 ... th+Scaling

[Akshay Desai]

Please see here for scaling the model.
https://simtk-confluence.stanford.edu:8 ... th+Scaling

Thank you for your reply @Karthick Sir. But I have read this manual earlier also, and I am still not clear with the usage of scale factor. Suppose if I want to make a subject for 172 height, what will I use the scale factor here as?

[Daniella Bianchi]

I too am very confused about how to calculate the scaling factor. If it is just an "overall scale factor s can then be used to scale any segments, and along any combination of the X, Y, and Z axe" how does the values for each body segment change? Where do you even find the model (say gait2354) distances to compute s = e/m? I am confused.

[Thomas Uchida]

Ideally, you would scale a full-body model using data from markers placed all over the body. Each body segment can then be scaled based on the markers affixed to that segment. If you have only the height of the model ("Suppose if I want to make a subject for 172 height"), you could (1) put a marker on the top of the model's head, (2) calculate the height of the generic model (e.g., in the ScriptingShell Window using the script below), (3) calculate the scale factor to match the subject's height (i.e., scale_factor = 172cm / current_height), and (4) enter this scale factor to "manually scale" all body segments by the same amount in all dimensions. You should expect large errors in the other dimensions of your model.

Code: Select all

model = getCurrentModel()
state = model.getWorkingState()
mHead = model.getMarkerSet().get('marker_name')
mHead.getLocationInGround(state)

[Jobin Geevarghese ThampI]

ok, height and weight dimensions will change once we scale the model, but what about other factors like age, can we change the age of the model in XML file, is it possible?...because I tried to change the age of the model in XML file, but I don't know how effective it will be

[Thomas Uchida]

There is no global "age" parameter you can use to automatically modify parameters throughout the model. However, once you decide which parameters you wish to modify and the calculations you want to use to modify them, you can write a script to modify all components in the model of that type.

[Jobin Geevarghese ThampI]

So, i was calculating the height of the model after placing a marker on the top of the head and I named the marker as 'head", also I entered the script which you posted here, and how can I get the value, I am new to OpenSim