Computational lithography, critical for advanced semiconductor manufacturing, demands high-performance rasterization to meet nanometer-scale precision. Traditional CPU-based rasterizers struggle with the increasing complexity and data volumes of modern designs. This paper presents a massively parallel GPU rasterizer designed to accelerate high-resolution mask synthesis, lithography simulation, and optical proximity correction (OPC). Our innovative GPU-accelerated approach leverages a GPU-friendly algorithm that ensures high precision, fractional pixel coverage, and connectivity preservation for sub-pixel geometries. Benchmarking on NVIDIA H100 GPUs demonstrates significant speedups—up to 290x for Manhattan shapes and 45x for curvilinear shapes—compared to highly optimized CPU algorithms, with less than 1 percent absolute error. This methodology provides a robust solution for the demanding computational requirements of next-generation lithography, enabling faster time to market and improved design quality.