BASH - Biomechanical Animated Skinned Human
Schleicher, R., Nitschke, M., Martschinke, J., Stamminger, M., Eskofier, B., Klucken, J., Koelewijn, A. (2021). BASH: Biomechanical Animated Skinned Human for Visualization of Kinematics and Muscle Activity. 16th International Conference on Computer Graphics Theory and Applications (GRAPP), 2021.
https://www.scitepress.org/Papers/2021/102106/102106.pdf
BASH Model
Converting a OpenSim [1] format file (.osim + .mot) to the SCAPE [2] framework. Visualization tool to inspect the animated model in 3D.
Processing Pipeline
Input Model: OpenSim
- Parser
- Model (.osim)
- Scale factors (.xml)
- Motion (.mot)
- Muscle Activation (.sto)
Baseline model Design for a new Musculoskeltal Model (in Blender)
- modeling
- import SCAPE mesh
- rig and skin skeleton (same hierarchy as musucloskeletal model)
- place markers (same set as musculoskeletal model)
- export model (.dae reorders vertices...) => mesh, markers & weights files
Scaling
- performed automatically, applied correctly to the hierachy, applied in bone space
- use .xml file or my estimation (defined in settings.h)
- scaled vs generic in ./data/cache/mesh/
Initial Pose Matching
- computed automatically using OpenSim's IK solver
- cached in ./data/cache/mapping for debugging the resulting .mot file
Pose Transformation
- calculated beforehand (needed the mesh for projection to SCAPE)
- uses pose mapping projection and kinematic transformations, applied in world space
- cached in ./data/cache/mesh/
Projection into SCAPE space
- projection to scape space (only relative rotations)
- rigid alignment to adjust translation
- cached in ./data/cache/mesh/
Visualization of Muscle Activation
- computed at run-time
- color coding in Fragment Shader
Settings
- settings.h for keyshortcuts, constants and other configurations
Project structure and dependencies
-
SCAPE: The main Windows-Application that handles the model conversion and visualization
-
External dependencies (minimum required version):
-
SFML (>= 2.5.1)
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glew (>= 2.1.0)
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glm (>= 0.9.9.5)
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Assimp (>= 3.0.0)
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OpenSim and SimbodyTK (>= 4.0)
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libRender: A custom framework used for creating a window and render a 3D-application in it
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External dependencies (minimum required version):
-
SFML (>= 2.5.1)
-
glew (>= 2.1.0)
-
glm (>= 0.9.9.5)
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libSCAPE: The SCAPE framework to load the SCAPE binary data and create a mesh in pose and shape
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External dependencies (minimum required version):
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SuitSparse package: suitsparse + amd + umfpack (>= 5.1.2)
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GSL (>= 2.4)
SCAPE Framework
- Implementation in ´SCAPE.h´
- Model parameters
- Pose: Rotation vector for each part ('numParts = 16') in three-dimensional twist subvectors (the axis is determined by the vector's direction and the angle is determined by the vector's magnitude.
- Shape: Scalar PCA coefficients ('numVecs = 20') to modify body proportions like height, size and gender etc.
Building platform x64
- OpenSim can only be built in 64bit. So we have to use the x64 Platform in order to use their API.
- Include and link all dependencies in x64.
- Build the SCAPE framework in x64.
- Define the flag '#define SAVE_MATRIX 0' once to write new binaries in the correct format (64bit wording).
- The folder 'data\default_scape_data' should contain the binary files: 'matrixDGrad.bin', 'SCAPE_DGrad_numeric.bin', 'SCAPE_DGrad_symbolic.bin', 'SCAPE_pose.bin'.
Example result
OpenSim's visualization compared to our visualization (data set: straight running [3]):
References
[1] Seth, A., Hicks, J. L., Uchida, T. K., Habib, A., Dembia,C. L., Dunne, J. J., Ong, C. F., DeMers, M. S., Ra-jagopal, A., Millard, M., et al. (2018). OpenSim: Sim-ulating musculoskeletal dynamics and neuromuscularcontrol to study human and animal movement. PLoSComputational Biology, 14(7):1–20.
[2] Anguelov, D., Srinivasan, P., Koller, D., Thrun, S., Rodgers,J., and Davis, J. (2005). SCAPE: Shape Completionand Animation of People. InACM Transactions onGraphics, volume 24, pages 408–416.
[3] Nitschke, M., Dorschky, E., Heinrich, D., Schlarb, H., Eskofier, B. M., Koelewijn, A. D., and Van den Bogert, A. J. (2020). Efficient trajectory optimization for curved running using a 3D musculoskeletal model with implicit dynamics. Scientific Reports, 10(17655).