  This paper investigates different approaches to build and use digital human
avatars toward interactive Virtual Co-presence (VCP) environments. We evaluate
the evolution of technologies for creating VCP environments and how the
advancement in Artificial Intelligence (AI) and Computer Graphics affect the
quality of VCP environments. We categorize different methods in the literature
based on their applications and methodology and compare various groups and
strategies based on their applications, contributions, and limitations. We also
have a brief discussion about the approaches that other forms of human
representation, rather than digital human avatars, have been utilized in VCP
environments. Our goal is to fill the gap in the research domain where there is
a lack of literature review investigating different approaches for creating
avatar-based VCP environments. We hope this study will be useful for future
research involving human representation in VCP or Virtual Reality (VR)
environments. To the best of our knowledge, it is the first survey research
that investigates avatar-based VCP environments. Specifically, the
categorization methodology suggested in this paper for avatar-based methods is
new.
