Abstract: Giant impacts play a central role in shaping planets, moons, and small bodies, yet their simulation has long been limited by computational constraints. In this talk, I will trace the methodological and technical path that has taken us from early smoothed particle hydrodynamics simulations with on the order of 10⁵ particles to today’s billion-particle calculations. I will highlight key scientific results obtained with the Gasoline code, focusing on how these simulations informed our understanding of impact outcomes. I will then introduce pkdgrav3, our next-generation massively parallel gravity–hydrodynamics code, and show how its novel architecture enables orders-of-magnitude increases in resolution and throughput. Using examples from several recent and forthcoming studies, I will illustrate what becomes possible when impacts can be simulated with unprecedented fidelity: extensive parameter sweeps at moderate resolution, and ultra-high-resolution flagship simulations capable of resolving previously inaccessible physical regimes. Together, these advances open a new era in which the diversity of planetary collisions, and their observable signatures, can be explored systematically and at scale.