Before revision:  We study the problem of computing the visibility polygon from a given viewpoint q inside \mathcal {P} where only few working variables can be used. The problem was previously solved in O(n ) time using O(1) variables for working space, where denotes the cardinality of reflex vertices of \mathcal P in the output .
After revision:  We study the problem of computing the visibility polygon from a given viewpoint q inside \mathcal {P} where only sub-linear variables are allowed for working space. Without any memory-constrained, this problem was previously solved in O(n ) time using O(1) variables for working space, where denotes the cardinality of reflex vertices of \mathcal P in the output .