Newbie question on lightmaps

I’m trying to understand how to use lightmaps, some things confuses me though.

What I understand is that every surface has it’s own lightmap. Lets take
a large wall for example. The wall is a large rectangle with 4 vertices. I place
a small texture on the wall that repeats itself, using glTexPar.(,GL_REPEAT).

Now, how large would my lightmap be? Same size as texture? Same size as
wall and then split into power-of-2 smaller lightmaps? Should I split my “large”
wall polygon into smaller parts from the beginning(when modelling)?

Thx in advance

normally a lightmap is shared between various surfaces, ie i believe for a q3a level there are only 6 lightmap textures to map the whole level. lightmaps are typically stored at a far lower resolution then the normally texture eg if u map a 256x256 texture to a wall the lightmap size that covers the wall will be about 16x16

Hi zed could you send me a detailed description of the lightmap. Or what do you mean wiht 6 lightmaps? How it works?