This research team has developed a learning trajectory on 3D visualization for elementary children. This paper focuses on the interchange among the three Spatial Operational Capacity framework representations, namely, 3D models, 2D conventional diagrams, and semiotic abstract representations, and the critical role of a dynamic computer interface that simulates the representations. The trajectory is described through an actions-on-objects (Connell, 2001) lens and the project's strong problem-solving approaches that are critical to its successful enactment. [For the complete proceedings, see ED585874.]