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