From MoCap to MMU
The first part describes how to get the motion file. One way to get the file is to execute this motion yourself and record it with a motion capture system. Common systems for this are for example the motion capture system from Xsens. In addition to the motion capture suit, Xsens also provides the software to capture, record and process the motion. After a successful capture, the motion is stored in MVN's own file format and can be processed in the program as desired. The recording can be cut in such a way that only the necessary motion for the animation is preserved. Finally, the finished edited motion must be exported as an FBX file.
Another way to get the motion file is to use motion libraries, which contain a set of animation files that can usually be purchased. The important thing here is that the file is a FBX format to use it for building a MMU.
The following is an example of how motion capture with Xsens MVN Analyzer works for an Xsens motion capture system. The manufacturer of the selected motion capture system provides detailed documentation (usually on the website) to obtain successful motion data. Xsens for example provides some helpful instructions and video tutorials.
- First, the Xsens system must be connected to the computer and recognized in MVN. In addition, the dimensions of the body on which the motion capture system will be applied must be entered or loaded from an existing file (see Fig. 1).
Fig. 1
- Now you can see in the program that the motion is transferred from the motion capture system to the digital human model, but the body is not displayed correctly (see Fig. 2). For this, a calibration process must be started. By pressing the "Start" button in the calibration window on the left side, the calibration can be started, by following the instructions on the screen (see Fig. 3). The calibration data is automatically processed and evaluated. If the calibration is successful, the actual recording can be started.
Fig. 2
Fig. 3
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The digital human model is now visualized as it should be. The recording can begin. The desired motions can be executed and saved in Xsens' own format at the end of the recording process. When saving, the recording is automatically post-processed to obtain clean and smooth motion data.
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For further processing of the motion data, it is necessary to export the motion data in a common data format like FBX. When exporting to MVN, the "Export Selection" option can be used to cut out the required sequence of the recording. To do this, the required frames must be selected at the bottom of the timeline. To help, markers can be set at the beginning and end of the sequence (see Fig. 4).
Fig. 4
Note that MVN exports the FBX files in ASCII format. If further post-processing or editing of the motion data with free software such as Blender is required, the FBX file must be converted to a binary data format. Free programs such as Autodesk FBX Converter are useful tools for this.