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Top1. Introduction
Sign Language is a visual/spacial language used by deaf individuals. No one form of Sign Language is universal; different Sign Languages are used in different countries or regions (C.Stokoe, 1960). In the USA, the language used by the deaf community is ASL (American Sign Language). In Tunisia, different Sign Languages are used in different regions. Unlike spoken language, Sign Languages are based on iconic signs (Cuxac, 2000; Edward & Ursula, 1988; Frishberg, 1975) which make this means of communication more complex.
Unfortunately, many studies and statistics raised serious concerns about deafness and literacy. Indeed, deaf individuals do not reach their potential in education especially in subjects like math science and engineering. Hearing impairment represents an obstacle to deaf and prevents them from having the same opportunities as hearing persons especially in job and social life. The main reason for the encountered difficulties to access to high level grades in curriculum is that deaf suffer from low literacy. In fact, in the USA, studies showed that less than 12% of deaf students at age 16 can read at a 4th grade reading level (Padden & Ramsey, 2000) .In Tunisia, according to a report published by the institute of promotion of people with disabilities, more than 90% of deaf are illiterate1. Similar rates were observed in almost the majority of African countries. In France, up to 80% of deaf suffer from illiteracy (Marc Renard) which leaves them far behind hearing persons in term of professional and social vocation.
Signing avatars have the potential to overcome the barriers faced by deaf people to access to sources of information. These 3D animated characters are able to interpret and provide Sign Language translation to any type of media including educational resources. Even though videos of real signers used to be the common way for providing signed translations to educational material as well as full dictionaries2 for many Sign Languages3, signing avatars are progressively replacing videos of real signers.
Signing avatars offer many advantages related to the pedagogic practices in education. It has been shown that using 3D characters to teach deaf individuals improved their English literacy (J, 2008). Moreover, many investigations concluded that teaching scientific subjects using signing animated characters is beneficial (Vesel, 2005) (Vesel J., 2005). This has been confirmed by researchers who created a 3D signing avatar called “Mathsigner” aiming to teach math to hearing impaired children (Adamo-Villani et al., An immersive virtual environment for learning sign language mathematics, 2006; Adamo-Villani, Doublestein, & Martin, 2005) (Adamo-Villani & al, An immersive virtual environment for learning sign language mathematics, 2006; Adamo-Villani, Doublestein, & Martin, 2005).
Alternatively, researchers and experts listed many benefits of 3D signing avatars related Computers and digital data. In fact, signing avatars systems are able to create digital signed contents that could be saved for later use. Moreover, several standards associated with 3D humanoids modeling and animation have been created (to be discussed in section 3) so it became possible to exchange 3D signed contents and reuse them in different scenarios by taking advantage of their interchangeability.
Unlike videos and besides the fact that 3D signing avatars guarantee the anonymity of signers, before rendering 3D signed scenes, it is possible to customize many parameters of the animation which is very useful for persons who are learning Sign Language. Thus, the background of the scene can be changed to get better clarity of the sign. The speed and rhythm of signing can be adjusted and the sign can be watched from many angles of view. All these features are accessible through convivial user interfaces and don’t need any programming skills since developers made great efforts to provide friendly and ease-of-use interfaces. Then, users are not supposed to master programming scripts and animation techniques when creating 3D signs.