More surfaces than needed look to be affected by light styles

[illwieckz]

Light style is a graphical effect where lightmaps are baked at map build time to be rendered with some mathematical functions (exampe: sine), this is useful to produce intermittent or varying lights while only relying on lightmaps.

With maps making use of this like tremor, pulse or gloom2, it appears more surfaces than needed are blinking.

I first considered it may be either a bug in q3map2, either a bug in the engine, but an original build that is rendered properly in tremfusion is misbehaving on dæmon.

[illwieckz]

The regression was introduced betseen 0.51 and 0.52, I have some ideas from where it may come.

When revamping the .shader material and GLSL shader code I rewrote entirely the stage collapsing code for legacy materials (fixing many bugs in the process and enabling features like multitextured terrain blending) and I had some doubt about what would be happening if there was more than one lightmap stage per material…