Before revision:  In this paper, we present an optimal in-place algorithmof O(n) time, and O(1) extra variables (in addition to the being in-place) for computing visibility area . If reporting the parts of \mathcal{P linear-time and in-place algorithm for computing visibility area of a viewpoint inside a simple polygon .
After revision:  In this paper, we present an optimal in-place algorithmof O(n) time, and O(1) extra variables (in addition to the being in-place) for computing visibility area , where c<n is the number of critical vertices. We keep the algorithm in the linear-time and in-place algorithm for computing visibility area of a viewpoint inside a simple polygon .