A geometry-based simulation (GBS) strategy is developed for modeling film growth, which avoids explicit treatment of the terrace diffusion of adatoms and their aggregation with islands - a computationally expensive component of either atomistic simulation or continuum analysis. GBS characterizes island growth in terms of capture zones (CZ's), and implements simple but realistic geometric rules to incorporate crucial spatial aspects of the island nucleation process, i.e., nucleation nearby CZ boundaries. This approach reliably predicts island size distributions and spatial correlations, and is especially efficient for highly reversible island formation.