--- /dev/null
+// dir_lights.cxx -- build a 'directional' light on the fly
+//
+// Written by Curtis Olson, started March 2002.
+//
+// Copyright (C) 2002 Curtis L. Olson - curt@flightgear.org
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+//
+// $Id$
+
+
+#include "dir_lights.hxx"
+
+
+// Generate a directional light
+ssgLeaf *gen_directional_light( sgVec3 pt, sgVec3 dir ) {
+}
--- /dev/null
+// dir_lights.hxx -- build a 'directional' light on the fly
+//
+// Written by Curtis Olson, started March 2002.
+//
+// Copyright (C) 2002 Curtis L. Olson - curt@flightgear.org
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+// General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+//
+// $Id$
+
+
+#ifndef _DIR_LIGHTS_HXX
+#define _DIR_LIGHTS_HXX
+
+
+#ifndef __cplusplus
+# error This library requires C++
+#endif
+
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <simgear/compiler.h>
+
+#include STL_STRING
+
+#include <plib/ssg.h> // plib include
+
+SG_USING_STD(string);
+
+
+// Define the various supported light types
+enum {
+ FG_RWYLIGHT_TAXI = 0,
+ FG_RWYLIGHT_VASI,
+ FG_RWYLIGHT_EDGE,
+ FG_RWYLIGHT_TOUCHDOWN,
+ FG_RWYLIGHT_THRESHOLD,
+ FG_RWYLIGHT_WHITE,
+ FG_RWYLIGHT_RED,
+ FG_RWYLIGHT_GREEN,
+ FG_RWYLIGHT_YELLOW
+} fgRunwayLightType;
+
+
+// Generate a directional light. This routines creates a
+// 'directional' light that can only be viewed from within 90 degrees
+// of the specified dir vector.
+
+// To accomplish this, he routine creates a triangle with the 1st
+// point coincident with the specified pt and the 2nd and 3rd points
+// extending upward. The 1st point is created with an 'alpha' value
+// of 1 while the 2nd and 3rd points are created with an 'alpha' of
+// 0.0.
+
+// If the triangle is drawn in glPolygonMode(GL_FRONT, GL_POINT) mode,
+// then two important things happen:
+
+// 1) Only the 3 vertex points are drawn, the 2nd two with an alpha of
+// 0 so actually only the desired point is rendered.
+
+// 2) since we are drawing a triangle, back face culling takes care of
+// eliminating this poing when the view angle relative to dir is
+// greater than 90 degrees.
+
+// The final piece of this puzzle is that if we now use environment
+// mapping on this point, via an appropriate texture we can then
+// control the intensity and color of the point based on the view
+// angle relative to 'dir' the optimal view direction of the light
+// (i.e. the direction the light is pointing.)
+
+// Yes this get's to be long and convoluted. If you can suggest a
+// simpler way, please do! :-)
+
+ssgLeaf *gen_directional_light( sgVec3 pt, sgVec3 dir );
+
+
+#endif // _DIR_LIGHTS_HXX