View Full Version : Maya Unit of Measure problem...

03 March 2006, 10:21 PM
I've never really understood what's going on with Maya's unit of measure. I realize that is arbitrary, but only really matters when going back and forth between models and their relative scale to one another. However, I just built a camera rig in a scene with 'Foot' as the unit of measure, and when I import it into any other scene it's way too small. So, I go up to the Settings/Prefs -> Settings -> Unit of Measure, and change it from centimeters to feet. (first of all in a scene with cent, a feet model should be huge, not small) When I change it to feet then the model gets even smaller. And how come when you change the unit of a scene that's already open, nothing really changes??

Please help, I'm working on an animatic for my grad project and need proper scale/translate values for camera measurements.

03 March 2006, 10:32 PM
Solving my own problem here...

In the userPrefs file there are two entries for default unit:

-sv "workingUnitLinear" "ft"
-sv "workingUnitLinearDefault" "cm"

I'm not sure what the difference is, but changing the second line to ft seemed to work. Can anyone explain the differnece?

03 March 2006, 12:45 AM
Maya has internal units that are used to do all calculations, and on the ohter hand, user defined units that Maya converts on the fly including the default angular unit - the degree which internally is radian. When you choose a new unit in the preferences, all numbers associated with the geometry will be converted to the new unit, except the scale values witch will remain relative to the unit they were created with.

To check how different units affect your scene, just create a cube and move it from its original position, then change the units while watching the channel box coordinates of the cube. After you changed the unit, create another cube in the same scene you will see a big size difference between the default cubes. You can also use some of the measure tools (including the Maya 7 Universal Manipulator) on objects and check how their numbers change when you change the units.

I use different units mostly while building a scene that has objects with very different sizes, for example a table with small objects in a huge room. While building the small objects and the table, I work with centimeters or inches, and when building the walls, I switched to meters or feet for convenience. Once everything is built I put the units back to the internal ones, especially before applying things like dynamics or some expressions which work best with the internal units.

I canít tell why your object is small when you import it in other scenes. Are you referring to numbers when you say it is small?.

03 March 2006, 12:49 AM
Actually you shed some very good light on my problem. When I created the scene for the first model, it must have been in cm even thought I believed it to be in feet. Scaling the model from 1 to 30.48 (how many cm are in 1 foot) it lined up. That told me my original scene was definately in cm. So changing the units doesn't change the scale, that makes a lot more sense now. Thank you!!

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03 March 2006, 12:49 AM
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