So what does any of this mean? The simple answer is that I can use the lightmap to change the appearance of parts of brush surfaces without creating a new texture or shader. This saves texture memory, pk3 file size, FPS, while giving us detail and control. What the water surface shader is doing is actually two-fold. There's the surface shader, then there's the undersurface shader. The surface shader is pretty normal, except that it uses q3map_cloneshader to call the dependancy undershader. Also note that cloneshader inherits the properties of the dependancy, such as q3map, surfaceparm, etc, but not shader passes (i.e. map { }). The undershader uses q3map_surfacelight and q3map_lightimage. The important part here is that it also uses q3map_invert. This inverts the shader face, so now it faces the underside of the brush. This causes the glow of surfacelight to point downward where we need it. The shader combo gives the mapper ease of use. Simply apply the reglow shader to the brush surface, and tweak the shader to your desire if you want. Why is this useful??? Come on you haven't figured it out yet? ;) You get far more realistic underwater lighting for no performance cost. Of course it's not completely free, you still have to compile -light right? hehe. Also, on these surfaces, I reduced _lightmapscale to something tiny like .125 which lined up the color edge. That's not necessary though. Also radiosity can clean the edges up a bit too. Possible downsides are that since it's the lightmap, having func_bobbing water might look slightly out of place. And maybe longer compile times. I can't think of any more... yeah!

// REGLOW SHADER
// Apply me to brush face! Reglow_assist shader handles the reverse surface.
textures/wilyduck_1/water_reglow
{

	qer_editorimage textures/wilyduck_1/duck_water2.tga
	qer_trans 0.5
	q3map_cloneshader textures/wilyduck_1/water_reglow_assist
	{
		map textures/wilyduck_1/duck_water2.tga
		blendfunc filter
		tcMod scroll 0.01 0.1
	}
	{
		map textures/wilyduck_1/duck_water2.tga
		blendfunc add
		tcMod turb 0 0.5 0.05 0.05
	}
	{
		map $lightmap 
		blendfunc filter
	}

}

// I reverse to become the inverted face. Go reglow! -wily_duck
textures/wilyduck_1/water_reglow_assist
{
	surfaceparm nolightmap
	surfaceparm nomarks
	surfaceparm nonsolid
	surfaceparm trans
	q3map_lightimage textures/wilyduck_1/duck_water2.tga
	q3map_surfacelight 1000
	q3map_invert
	{
		map textures/wilyduck_1/duck_water2.tga
		blendfunc filter
		tcMod scroll 0.01 0.1
	}
	{
		map textures/wilyduck_1/duck_water2.tga
		blendfunc add
		tcMod turb 0 0.5 0.05 0.05
	}
	{
		map $lightmap 
		blendfunc filter
	}
}