Agenda

Love and Deepspace is a mobile game dedicated to providing players with a near-realistic romantic experience. Providing realistic rendering on mobile devices is our constant goal. Global illumination is one of the most challenging technical issues. Mobile platforms have significant constraints in terms of memory, bandwidth, and hardware performance, making traditional algorithms difficult to directly apply. This was especially true after we introduced user-generated content (UGC) gameplay. Players can customize scenes and lighting, making changes in real time. Traditional static baking algorithms are unable to cope with such flexibility.

We developed a real-time GI algorithm based on Surfel and 3D Radiance Cascade, which runs smoothly on mobile, supports dynamic transformations of objects and light sources, and offers performance comparable to mainstream PC algorithms. We precalculate surfel data during the model asset importing phase, avoiding any baking operations during game runtime or scene editing, and achieving near-fully dynamic global illumination.

Takeaway

How to pre-generate surfels on a per-asset basis, how to perform software ray tracing on them, and how to resolve gaps between surfels.

Optimize surfel ray tracing performance using 3D Radiance Cascade.

Significantly improve performance using surfel BVH and a hash cache for storing collision points.