Before revision:  We study the problem of computing the visibility polygon from a given viewpoint q in \({\mathcal {P}\) where only O(1) workspace is available}  }  . The problem was previously solved in O( cn) time , where c denotes the number of critical vertices for q which are the vertices of \({\mathcal {P}\) where the visibility region changes.
After revision:  We study the problem of computing the visibility polygon from a given viewpoint q }\) where only O(1) workspace is available} } . The problem was previously solved in O( cn) time , where c denotes the number of critical vertices for q which are the vertices of \({\mathcal {P}\) where the visibility region changes.