A method to incorporate Spherical Harmonic into URP for Real-Time Global Illumination in Unity Universal Render PipeLine

Abstract

As the size of the gaming market continues to grow, game engines like Unity and Unreal are constantly being developed and updated for multi-platform support. In particular, Unity divides the Render Pipeline to be used. Among them, the Universal Render Pipeline (URP) has the advantage of supporting various platforms while improving performance by reducing draw calls and batches at the same quality settings and reducing the load on the CPU and GPU. However, only limited global illumination is supported in the real-time 3D rendering area within URP, such as Baked GI and Enlighten GI, and Enlighten GI will be deprecated after 2024LST, so real-time global illumination is not available in URP, which may reduce the realism and immersion of global illumination in games or applications that use URP. The main objective of this research is to incorporate precomputed spherical harmonics into URP to enable dynamic GI updates in real-time. The approach proposed in this research is to compute the coefficients of spherical harmonics offline and then run them within the URP rendering pipeline, where work exists to effectively simulate dynamic lighting conditions. To demonstrate this, experiments were conducted by changing the rotation and color of the lights, and a comparative analysis was performed to demonstrate the effectiveness of the theory proposed in this work.