This study compares the different degrees of realism conveyed by physical models and real-time rendered virtual prototypes. Using scaled physical models, scaled virtual prototypes, and full-scale virtual prototypes as stimuli, the authors conducted experiments to investigate perception of realism with respect to six sets of attributes: form, lighting and shadow, details, color, material, and total effect. Overall, the authors found that scaled physical models conveyed the highest degree of realism, followed by full-scale virtual prototypes, and then scaled virtual prototypes. With respect to form attributes, full-scale virtual prototypes delivered better realism than scaled physical and virtual models, where the differences are significant between full-scale and scaled virtual prototypes. Thus, being able to view form features in full size appears to be important in perceiving objects' forms. With respect to lighting and shadow as well as color and material attributes, scaled physical models conveyed higher degree of realism than full-scale or scaled virtual prototypes. In terms of detailed attributes, full-scale virtual prototypes provided better realism than scaled virtual prototypes, but not significantly better than scaled physical models. For total effect attributes, scaled physical models conveyed the highest degree of realism, followed by full-scale virtual prototypes, and then scaled virtual prototypes.