Triply periodic diamond, cubic, and gyroid structures are studied as templates for the fabrication of 3D photonic crystals (see figure). The achievable backfilling volume fraction and bandgap properties are analyzed by considering the pinch-off of level surfaces. The conformal coating on such templates is found to result in incomplete filling and loss of the photonic bandgap. An attempt to solve this problem is made by using electrophoretic deposition, which results in a nearly completely filled 3D titania structure.