We explore the effect of separation between the faces of a corner-cube reflector on its performance. This is important because, in several retroreflector applications, one (or more) face of the module is some type of modulator. The fabrication and assembly of these modules invariably results in, or requires, gaps between the faces. A two-dimensional aperture optical model is developed to analyze the effect of this separation on performance. A geometric optics approach is used to evaluate the consequence of the separation on the effective retroreflection area. Diffraction effects are then included to provide a complete model of the corner cube retroreflector (CCR). The results show that the separation-to-face length ratio (δ/L) is an important parameter in maximizing performance of the retroreflector module. We show that an increasing δ/L results in a rapid reduction in the retroreflected power. A CCR illuminated along the body-center direction, which yields the highest effective area, sees a 58% reduction in retroreflected power when δ/L=0.2. Consequently, the field of view of the retroreflector reduces significantly. On the basis of this work, we propose that an effective triface retromodulator could be a GaAs-on-Si modulator grown on a silicon precision corner-cube array, thus filling the entire surface with active material.