A code sample for LÖVR that calculates a lightmap, while maintaining app responsiveness. The lightmap includes direct light and shadow, indirect bounce lighting, and ambient occlusion. The calculation is programmed in Lua, and can be run in a LÖVR project without additional external dependencies.
The project uses a simple, limited data representation. A type called GeoFace
is implemented in geoface.lua, alongside a hand-written sample scene. A
GeoFace defines colored rectangles.
To maintain responsiveness, the lightmap is calculated using worker threads. A
scheduler thread is implemented in scheduler.lua, which manages the whole
process, and acts as an intermediary between the main thread and the worker
threads.
The worker threads are implemented in worker.lua. They wait for jobs to come
in on a queue, and invoke tasks implemented in the tasks/ folder accordingly.
There are three tasks used to implement different lightmap passes: direct, bounce, and ambient occlusion.
The direct lighting pass calculates light contribution from a point light source, attenuating based off of distance and facing, with shadows based on occluding geometry. A configurable quality setting allows multiple samples to be taken per sample from slightly offset positions, to anti-alias the shadow.
Bounce lighting allows surfaces to receive light reflected off other surfaces. The bounced lighting accounts for surface color. Rays are cast randomly, and a denoiser cleans the image at the end.
An ambient occlusion pass paints artificial darkness into corners and crevices, enhancing the sense of definition. Rays are cast out a limited distance, and the surface is darkened based on how many rays hit another surface, and how close those hits are to the surface.
Normal bilinear texture filtering produces a noticeable blocky pattern that stands out for the large texel sizes of a lightmap. A shader-based bicubic texture sampler smooths out shadow edges. Combined with the anti-aliasing from the direct lighting pass, shadows have minimal artifacting.