Synthetic terrain generation and scene generation is a critical component of performing meaningful simulation assessments across many simulation domains. The U.S. Army Combat Capabilities Development Command Aviation and Missile Center (CCDC AvMC) has developed a process for rapidly generating and characterizing large-scale, multispectral terrain models and thermal signatures for use in a wide range of simulation tools from ground vehicles and air platforms to smart weapons and AI algorithms. This process has allowed the replacement of legacy terrain generation methods of on-site collections or statistics-based models with high-fidelity, physics-based terrain signature modeling at a fraction of the schedule and cost by leveraging modern high-performance computing paradigms and algorithms. This allows for rapid generation of terrain models of any location in the world at any time of day or season.