Fresnel diffraction plays a central role in simulating light propagation for holography and other coherent imaging systems. However, computing coherent light transport is computationally demanding because every object point can contribute to every hologram pixel, requiring specialized algorithms. Furthermore, the highly oscillatory nature of wavefronts forces dense sampling to maintain accuracy. We present an overview of phase-space decomposition techniques to accelerate numerical diffraction calculations. Moreover, we introduce a mipmap-inspired phase-space representation that significantly reduces scene sampling requirements for computer-generated holography. Our methods provide an analytical framework, implementation strategy, and performance analysis demonstrating substantial improvements over conventional ray-to-wavefront conversion techniques.