source: http://shaderlab.com/q3map2/lmt.txt

Lightmapped terrain: The quick and dirty Q3Map2 how-to.
Revision 2: 2002-11-30

Note: lightmapped terrain is a hack, and as such, has limitations. Shader effects such as environment mapping might be a little flaky because of the borked vertex normal on lightmapped terrain faces. This is necessary to enable lightmaps on nonplanar geometry.


Before you make ANY terrain with Q3Map2, your terrain shaders (typically textures/common/terrain and terrain2) must have the "q3map_terrain" keyword. Terrain is handled completely differently than from previous versions of Q3Map, and as such, it doesn't have any built-in shader name mangling for terrain entities.


The terrain shader MUST BE LISTED IN SHADERLIST.TXT or this will NOT WORK.


Use the following crib sheet to convert a typical terrain shader into lightmapped terrain:


// old-style vertex lit terrain shader

textures/terrain/hillside_0
{
	q3map_forcesunlight
	q3map_novertexshadows
	surfaceparm nolightmap
	
	{
		map textures/terrain/hillside_0.tga
		tcMod scale 0.05 0.05
		rgbGen vertex
	}
}



// update 2002-11-30, base terrain shader (Q3Map 2.3.x)

textures/terrain/hillside_base
{
	// required
	q3map_tcGen ivector ( 256 0 0 ) ( 0 256 0 )	// project texture every 256 units in X and Y
	q3map_lightmapaxis z						// project lightmap on z axis (up/down)
	
	// optional
	q3map_lightmapmergable						// merges all terrain into one seamless lightmap (no seams)
	q3map_lightmapsamplesize 32					// sets lightmap sample size to 2x normal to save mem			
}



// lightmapped terrain shader

textures/terrain/hillside_0
{
	q3map_baseshader textures/terrain/hillside_base	// instructs q3map2 to use this shader as a template
	
	{
		map textures/terrain/hillside_0.tga
	}
	{
		map $lightmap
		blendFunc GL_DST_COLOR GL_ZERO
	}
}




// lightmapped terrain shader for blending between two layers

textures/terrain/hillside_0to1
{
	q3map_baseshader textures/terrain/hillside_base
	
	{
		map textures/terrain/hillside_0.tga
	}
	{
		map textures/terrain/hillside_1.tga
		blendFunc GL_SRC_ALPHA GL_ONE_MINUS_SRC_ALPHA
		alphaGen vertex
	}
	{
		map $lightmap
		blendFunc GL_DST_COLOR GL_ZERO
	}
}