1 // pt_lights.hxx -- build a 'directional' light on the fly
3 // Written by Curtis Olson, started March 2002.
5 // Copyright (C) 2002 Curtis L. Olson - http://www.flightgear.org/~curt
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
24 #ifndef _SG_PT_LIGHTS_HXX
25 #define _SG_PT_LIGHTS_HXX
29 # error This library requires C++
33 #include <simgear/compiler.h>
36 #include <vector> // STL
38 #include <simgear/math/sg_types.hxx>
39 #include <simgear/scene/material/matlib.hxx>
45 typedef vector < int > int_list;
46 typedef int_list::iterator int_list_iterator;
47 typedef int_list::const_iterator int_point_list_iterator;
50 // Generate a directional light. This routines creates a
51 // 'directional' light that can only be viewed from within 90 degrees
52 // of the specified dir vector.
54 // To accomplish this, he routine creates a triangle with the 1st
55 // point coincident with the specified pt and the 2nd and 3rd points
56 // extending upward. The 1st point is created with an 'alpha' value
57 // of 1 while the 2nd and 3rd points are created with an 'alpha' of
60 // If the triangle is drawn in glPolygonMode(GL_FRONT, GL_POINT) mode,
61 // then two important things happen:
63 // 1) Only the 3 vertex points are drawn, the 2nd two with an alpha of
64 // 0 so actually only the desired point is rendered.
66 // 2) since we are drawing a triangle, back face culling takes care of
67 // eliminating this poing when the view angle relative to dir is
68 // greater than 90 degrees.
70 // The final piece of this puzzle is that if we now use environment
71 // mapping on this point, via an appropriate texture we can then
72 // control the intensity and color of the point based on the view
73 // angle relative to 'dir' the optimal view direction of the light
74 // (i.e. the direction the light is pointing.)
76 // Yes this get's to be long and convoluted. If you can suggest a
77 // simpler way, please do! :-)
79 osg::Node *SGMakeDirectionalLights( const point_list &nodes,
80 const point_list &normals,
81 const int_list &pnt_i,
82 const int_list &nml_i,
83 SGMaterialLib *matlib,
84 const string &material,
87 // Specify the way we want to draw directional point lights (assuming the
88 // appropriate extensions are available.)
90 void SGConfigureDirectionalLights( bool use_point_sprites,
91 bool enhanced_lighting,
92 bool distance_attenuation );
95 #endif // _SG_PT_LIGHTS_HXX