Dear Dr. Cabell,
perhaps the papers and the information below may clarify the process of motion capture without markers:

- "Combining 3D Flow Fields with Silhouette-based Human Motion Capture for Immersive Video" - pdf file
https://cs.stanford.edu/people/theob...lications.html
Christian Theobalt, Joel Carranza, Marcus A. Magnor, Hans-Peter Seidel
MPI Informatik - Saarbrücken, Germany - 2004

- BioMotion Laboratory - Stanford University
https://web.stanford.edu/group/biomo...arkerless.html

- "Capturing and Animating Skin Deformation in Human Motion"
Sang Il Park, Jessica K. Hodgins
https://www.google.com/url?sa=t&rct=...A-XDVUbRI8fG3_
School of Computer Science Carnegie Mellon University
The Carnegie Mellon Graphics Lab
http://graphics.cs.cmu.edu/projects/muscle/


commercial systems:
- The Captury
http://thecaptury.com/

- Dari Motion
http://darimotion.com/

- zFlo Motion
Motion Metrix system
https://www.zflomotion.com/

I hope this information is useful.
Best Regards,