I'm working on a glow effect that illiuminates lower parts of walls if the floor in my scene has a glowing texture. My problem: I cannot use any texture atlas or uv lightmaps and the wall polygons can be quite large so that the base texture can repeat. Can I do this somehow with a single lightmap texture and multitexturing and GLSL or do I have to render smaller polygons in a second passe?
Since the base texture gets darkened by the ambient vertex color in the first pass I'm afraid that the lighting effect will not be satisfactory when I use multiple passes.

Any ideas in how to make this work?