Additive lithography for electronics (ALE) is a process derived from Vat Photopolymerization. It combines high-resolution photopolymerization with conductive material deposition, enabling new approaches to microscale electronic packaging and fabrication. Accurately modeling light-material interactions during the curing process is essential for achieving fine spatial control and reliability. However, challenges arise due to complex phenomena such as scattering, reflection, refraction, and evolving optical properties of the resin during exposure—especially when printing on heterogeneous substrates or embedding conductive tracks. [1] Current simulation tools often rely on homogenized light source models that overlook complex optical effects such as localized scattering, reflection, and refraction. These simplifications fail to capture the evolving optical properties of the resin during curing and the role of embedded features. In this paper, we present a GPU-accelerated volumetric ray tracing framework designed to resolve key light-material interactions in ALE processes [2]. The tool models scattering, refraction, and rough surface reflections, and supports spatially varying refractive index profiles, including gradient-index (GRIN) materials. Preliminary simulation results indicate that light scattering off the substrate can significantly affect curing uniformity and accuracy. The ray tracer is engineered for integration into a Finite Element Method (FEM) simulation [3], allowing coupled two-way interaction between light propagation and curing kinetics. This framework lays the foundation for micro-scale predictive modeling and in-process control of ALE processes, and can be used to investigate largely unexplored effects of micro-scale light-material interaction.