1. A method implemented by data processing apparatus, the method comprising: obtaining a model of a building wherein the model comprises representation of the building at a point in time in construction of the building, and wherein the model contains a plurality of building objects that are indicated as being present in the building at the point in time by a construction schedule; identifying one or more candidate edges of the building objects, wherein a candidate edge is an outer edge of a slab building object, an edge of an opening in a slab building object, or a lower edge of an opening in a wall building object; analyzing the one or more candidate edges to identify one or more dangerous edges, wherein a dangerous edge presents a risk of falling; and generating a presentation of the building based on the model of the building wherein one or more of the identified dangerous edges are emphasized in the presentation.