Motion capture |
  
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Motion capture |
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Motion capture based movements can be applied on the digital human model. Both full body movements and movements of specific bodyparts are supported.
For this purpose MoCap data a special kind of task type has been developed (MoCap data) which enables seamless integration of motion capturing based movements with existing parametrical tasks. This new task is able to transfer file based motion data with the help of a mapping table to the digital human model. This mapping table maps the bodypart names in the external file to the internal bodypart names.
Requirements
▪motion data in Biovision hierarchy format (bvh) (see figure Structure of a bvh file)
▪a bodypart mapping table in csv format, which maps the external bodypart names from bvh file to the internal bodypart names (see figure Body part mapping table)
iExamples of bodypart mapping tables can be found in the installation folder under C:\Program Files\ema Software Suite\emaWorkDesigner\Manual\MoCap. |
ema human model structure
For creating the bodypart mapping table internal names of bodyparts / joints are necessary (see figure Skeletal structure of ema).
Figure 196: Skeletal structure of ema
Body part mapping table
Purpose of the body part mapping table is to map the definitions from the bvh file to the internal ema structures. Bodypart names can vary with the bvh file. Therefore the user has to ensure that the mapping information is correct.
iLines within in the file which are beginning with "//" will be handled as comments and therefore ignored during file parsing. |
Mapping file contains two parts GENERAL and BODYPARTS. First part (GENERAL) contains a parameter called pScalingFactorToMillimeters which has to be defined in order to map the bvh files units to the ema internal unit which is in millimeters. Examples:
▪bvh position information in meters -> correct scaling factor "1000"
▪bvh position information in inch -> correct scaling factor "25.4"
If the scaling factor has been set incorrect, position changes in the resulting movements will be either unrealistically big or small.
Area BODYPARTS contains a mapping table with bodypart names from bvh file (BodyPartExtern) and the corresponding names from ema (BodyPartIntern). If required, an additional column ConversionMatrix allows a mapping between external and internal bodypart coordinate systems (default is a 4x4 unity matrix) (see see figure Body part mapping table)
Figure 197: Body part mapping table
Motion data – bvh format
BVH is a text based file format. It contains a hierarchical description of the underlying digital human model. A Name, an Offset (local position) and 3 to 6 transformation Channels for rotations and translations are defined for every single joint. Second part of the file contains the movement data in a table structure. Every column represents one of the previously defined transformation channels in the order they have been defined. Each row represents a single frame of the movement keeping the values for the defined channels. In short, each row represents the individual poses/keyframes captured.
Figure 198: Structure of a bvh file