“…where Φ is constrained to take the linear form. In order to learn the low dimensional subspace Ω of hand configuration constrains, PCA is performed on joint locations in the training dataset [12]. E = [e 1 , e 2 , · · · , e M ] are the principal components, α = [α 1 , α 2 , · · · , α M ] T are the coefficients of the principal components, u is the empirical mean vector, and M 3 × K. As proved in the supplementary material, given the linear constrains of Φ, the optimal coefficient vector α * = [α * 1 , α * 2 , · · · , α * M ] T is:…”