I can see a terrain casting shadows on blocks crazy Look at this:

Click to reveal..



I did some test and checked the terrain lightmap color by myself.

Click to reveal..

Code:
var my_floor_ambient ()
{
	if ( !me )
		return 0;
//	set ( my, LIGHT | UNLIT );
	vec_set ( &my->blue, COLOR_WHITE );

	VECTOR vPos;
	vec_set ( &vPos, &my->x );
	vPos.z -= 300 - my->min_z;
	you = NULL;
	var height = c_trace ( &my->x, &vPos, IGNORE_ME | IGNORE_MODELS | IGNORE_SPRITES | SCAN_TEXTURE );
	if ( HIT_TARGET )
	{
		if ( you ) // if you exits, is a terrain for sure
		{
			if ( you->lightmap )
			{
				BMAP *bmpSkin1 = ent_getskin ( you, 1 );
				var scale = bmap_width(you->lightmap) / bmap_width(bmpSkin1); //
				var format = bmap_lock ( you->lightmap, 0 );
				var cX = hit.u1 * scale;
				var cY = hit.v1 * scale;
				var pixel = pixel_for_bmap ( you->lightmap, cX, cY );
				COLOR col;
				pixel_to_vec ( &col, NULL, format, pixel );
				vec_set ( &my->blue, &col );
//				vec_set ( &col, COLOR_WHITE );
//				pixel = pixel_for_vec ( &col, 100, format );
//				pixel_to_bmap ( you->lightmap, cX, cY, pixel );
				bmap_unlock ( you->lightmap );
				set ( my, LIGHT | UNLIT );
			}
		}
		else // hit a block
		{
			reset ( my, LIGHT | UNLIT );
//			vec_set ( &my->blue, &hit.blue );
		}
	}
	return height;
}




and I use vecLight as ambient color into the shader
Code:
float4 color = float4(vecEmissive.xyz * vecColor.xyz, 0) + vecAmbient * vecLight;