The dynamic mean-field density functional method is adapted to describe phase separation in the presence of geometrical constraints. We observe that inclusion of small filler particles (such as rods) already has a dramatic effect on the morphology of polymer melts. The effect is comparable to the effect of applied simple steady shear. Mesostructures in the presence of large filler particles such as plates are totally governed by the geometry of the particle. Effects of polymer-surface interactions on morphology formation are investigated in detail.