Lightmapping

What are lightmaps? And how to use them when making your game.

Lightmaps exist to allow highly detailed shadows/light that will run smoothly on low-end hardware.

When to Use?

You want shadows, but are targetting devices that don’t have the CPU/GPU power to compute them in real-time.
- Mobile games.
- F2P PC games that require lot of users.
You want better quality lighting than real-time lighting can currently deliver.
- Unity 5’s Precomputed GI tries to bridge this gap by allowing real-time light bounces.

A lightmap is a texture that contains lighting information.

Light is precalculated (baked) then layered on top of your main textures.

They are stored in memory when a level is loaded, so no CPU usage is required to display the lighting.

Traditional lightmapping requires the lightmap to be “layered” on top of a diffuse map.

Good in-game performance because the lighting/shadows were calculated in advance.
Time spent calculating lighting/shadows offline can equate to more realistic lighting in-game.
Allows for bounced lighting. (Note: Unity 5+ can do real-time bounced with Pre-Computed GI)

Time-consuming.
Uses up memory, depending on quality/resolution.
For static geometry only. Cannot be updated in real-time or generated in-game. Opening/closing doors will be a problem.
Dynamic objects can sometimes “stand out” from lightmapped geometry. They have to be lit seperately by Light Probes.
Increases file size of application.

TODO: Link to lighting reference page… Quake was the first game to use lightmaps.

http://polycount.com/discussion/76554/lightmaps-tech-pros-and-cons
https://unity3d.com/learn/tutorials/topics/graphics/starting-precompute-process
https://unity3d.com/learn/tutorials/topics/graphics/introduction-precomputed-realtime-gi (Added 19 May 2017)
https://tf2maps.net/threads/guide-lightmap-optimization.33113/
https://tf2maps.net/threads/tutorial-understanding-lightmaps.1693/
http://www.hourences.com/tutorials-ue3-lightmapping/
https://developer.valvesoftware.com/wiki/Lightmap