We model the visual interpolation of missing contours by extending contour fragments under a smoothness constrain. Interpolated trajectories result from an algorithm that computes the vector sum of two fields corresponding to different unification factors: the good ontinuation(GC) field and the minimal path (MP) field. As the distance from terminators increases, the GC field decreases and the MP field increases. Viewer- independent and the viewer-dependent variables modulate GC-MP contrast (i.e., the relative strength of GC and MP maximum vector magnitudes). Viewer-independent variables include the local geometry as well as more global properties such as contour support ratio and shape regularity. Viewer-dependent varaiables include the retinal gap between contour endpoints and the retinal orientation of their stems.GC-MP contrast is the only free parameter of our field model.In the case of partially occluded angles,interpolated trajectories become flatter as GC-MP contrast deceases. Once GC-MP contrast is set to a specific value,derived from emperical measures on a given configuration,the model predicts all interpolation trajectories corresponding to different types of occlusion of the same angle.Model predictions fit psychophysical data on the effects of viewer-independent and viewer-dependent variables.