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Facial Motion Capture for Games

Facial Motion Capture for Games. Adam Schwartz 12/01/2010. Introduction. State of the art: High end face animations: Cryengine Common / lowspec: Unreal Engine Regardless of tech, facial animation is now commonplace in games. Bones.

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Facial Motion Capture for Games

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  1. Facial Motion Capture for Games Adam Schwartz 12/01/2010

  2. Introduction • State of the art: • High end face animations: Cryengine • Common / lowspec: Unreal Engine • Regardless of tech, facial animation is now commonplace in games.

  3. Bones • Full Body Animation: Motion Capture is expressed on bones. • Unlike human bones, which provide structure for movement by muscles. • Animation bones: drive the movement of a structure composed of vertices; can be skinned (attached) to any kind of geometry.

  4. Bones • Simple construction • Easy characterization • Streamlined connection to motion capture

  5. Facial Animation: Motion capture is not usually done with bones, but with Blendshapes • Blendshapes: Predefined deformations of facial geometry. Unlike skeletons, these can’t be transferred to alternative geometry. Must have specific deformations for each of Motionbuilder’s Generic Expressions

  6. Blendshape Animation Example

  7. Blendshapes: Conclusions • Good for one character, not many. • Require significant artistic skill. • Alternative: Bones • Problem: Bone-based animation is standardized in Motionbuilder… but only for body animation.

  8. Skeleton as Clusters: An Alternative • Workaround: Cluster Groups • Bones ~ clusters • Bones can be reskinned regardless of geometry. • Weights can be adjusted faster than defining new blendshapes.

  9. Tools: Mocap • Motion Capture Lab in Department of Industrial Engineering • Vicon System • 4 megapixel cameras (120 Hz), SOA • 10 motion cameras, 2 video • cameras, passive reflective • markers • Four force plates to measure forces on ground • Facial expressions, electromagnetic device capture voltage in max 16 muscles

  10. Alternative Mocap • Active Marker systems (LED, etc) • Markerless Vision-Based • Non-Optical • Future: Mova Contour Reality Capture • 25 passive markers (for face) is sufficient.

  11. Tools: Software • Autodesk Maya 2010 • Autodesk Motionbuilder 2010 • Alternatives: Autodesk 3dsmax, Blender

  12. The Process • Import mocap data to Motionbuilder, connect to the “actor”.

  13. The Process • Express the actor on a “character” - a skeleton without bound skin geometry. • Characterize body as usual. • Characterize face as movements of the face’s bones instead of blendshape percentages.

  14. The Process • Plot all animations to the skeleton.

  15. The Process • An identical skeleton is resized and skinned to the character geometry in Maya, exported to Motionbuilder, and merged.

  16. The Process • The character is sent back to Maya, paint to adjust weights. • Group teeth, eyes, etc with relevant bones. • Animate Blinking. • Manually make final adjustments with keyframing.

  17. Character

  18. Side By Side

  19. Related Work • Standard Blendshape Method: Not transferable between characters, requires artistic skill. Very realistic results. (Autodesk, 2009) • Cluster group animation: Not transferable between characters. No significant artistic skill needed. Result quality is between bones and blendshapes. (3D Buzz, 2010) • Alternative bone-based rigs: Not standardized (yet)… • Updates to Maya to expand skeleton/mocap functionality. (Autodesk, 2010)

  20. References, Resources, Further Reading • Expressive Facial Gestures From Motion Capture Data by Eunjung Ju and Jehee Lee (EUROGRAPHICS 2008 / G. Drettakis and R. Scopigno • (Guest Editors) Volume 27 (2008), Number 2 • Joint Based Facial Rig by Mathew Smith www.jessieamadio.com/wordpress/?p=65 • Full-Body Character Riggingand Facial Motion Capture by Matthew Wynne http://www.mwynneconsulting.com • Maya/Motionbuilder Cluster Tutorials - http://www.3dbuzz.com • Tutorials and Forums at area.autodesk.com • Autodesk Maya 2010. San Rafael, California: Autodesk, Inc., 2009. Program documentation. • Motionbuilder Issue 4 http://www.3dbuzz.com/vbforum/sv_showvideo.php?v=1131, retrieved on 5 May 2010 • Autodesk HumanIK http://usa.autodesk.com/adsk/servlet/pc/index?id=9491249&siteID=123112 , retrieved on 1 Dec 2010

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