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flightgear/Main/views.cxx
curt 330c78ac73 Added ground collision detection.
Did some serious horsing around to be able to "hug" the ground properly
  and still be able to take off.
Set the near clip plane to 1.0 meters when less than 10 meters above the
  ground.
Did some serious horsing around getting the initial airplane position to be
  correct based on rendered terrain elevation.
Added a little cheat/hack that will prevent the view position from ever
  dropping below the terrain, even when the flight model doesn't quite
  put you as high as you'd like.
1998-07-12 03:14:42 +00:00

606 lines
20 KiB
C++

// views.cxx -- data structures and routines for managing and view
// parameters.
//
// Written by Curtis Olson, started August 1997.
//
// Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
//
// 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.
//
// $Id$
// (Log is kept at end of this file)
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <Debug/fg_debug.h>
#include <Flight/flight.h>
#include <Include/fg_constants.h>
#include <Math/mat3.h>
#include <Math/polar3d.hxx>
#include <Math/vector.hxx>
#include <Scenery/scenery.hxx>
#include <Time/fg_time.hxx>
#include "options.hxx"
#include "views.hxx"
// This is a record containing current view parameters
fgVIEW current_view;
// Constructor
fgVIEW::fgVIEW( void ) {
}
// Initialize a view structure
void fgVIEW::Init( void ) {
fgPrintf( FG_VIEW, FG_INFO, "Initializing View parameters\n");
view_offset = 0.0;
goal_view_offset = 0.0;
winWidth = 640; // FG_DEFAULT_WIN_WIDTH
winHeight = 480; // FG_DEFAULT_WIN_HEIGHT
win_ratio = (double) winWidth / (double) winHeight;
update_fov = TRUE;
}
// Update the field of view parameters
void fgVIEW::UpdateFOV( fgOPTIONS *o ) {
double theta_x, theta_y;
// printf("win_ratio = %.2f\n", win_ratio);
// calculate sin() and cos() of fov / 2 in X direction;
theta_x = (o->fov * win_ratio * DEG_TO_RAD) / 2.0;
// printf("theta_x = %.2f\n", theta_x);
sin_fov_x = sin(theta_x);
cos_fov_x = cos(theta_x);
slope_x = - cos_fov_x / sin_fov_x;
// printf("slope_x = %.2f\n", slope_x);
// calculate sin() and cos() of fov / 2 in Y direction;
theta_y = (o->fov * DEG_TO_RAD) / 2.0;
// printf("theta_y = %.2f\n", theta_y);
sin_fov_y = sin(theta_y);
cos_fov_y = cos(theta_y);
slope_y = cos_fov_y / sin_fov_y;
// printf("slope_y = %.2f\n", slope_y);
}
// Update the view parameters
void fgVIEW::Update( fgFLIGHT *f ) {
fgOPTIONS *o;
fgPoint3d p;
MAT3vec vec, forward, v0, minus_z;
MAT3mat R, TMP, UP, LOCAL, VIEW;
double ntmp;
o = &current_options;
if(update_fov == TRUE) {
// printf("Updating fov\n");
UpdateFOV(o);
update_fov = FALSE;
}
scenery.center.x = scenery.next_center.x;
scenery.center.y = scenery.next_center.y;
scenery.center.z = scenery.next_center.z;
// printf("scenery center = %.2f %.2f %.2f\n", scenery.center.x,
// scenery.center.y, scenery.center.z);
// calculate the cartesion coords of the current lat/lon/0 elev
p.lon = FG_Longitude;
p.lat = FG_Lat_geocentric;
p.radius = FG_Sea_level_radius * FEET_TO_METER;
cur_zero_elev = fgPolarToCart3d(p);
cur_zero_elev.x -= scenery.center.x;
cur_zero_elev.y -= scenery.center.y;
cur_zero_elev.z -= scenery.center.z;
// calculate view position in current FG view coordinate system
// p.lon & p.lat are already defined earlier, p.radius was set to
// the sea level radius, so now we add in our altitude.
if ( FG_Altitude * FEET_TO_METER >
(scenery.cur_elev + 3.758099 * METER_TO_FEET) ) {
p.radius += FG_Altitude * FEET_TO_METER;
} else {
p.radius += scenery.cur_elev + 3.758099 * METER_TO_FEET;
}
abs_view_pos = fgPolarToCart3d(p);
view_pos.x = abs_view_pos.x - scenery.center.x;
view_pos.y = abs_view_pos.y - scenery.center.y;
view_pos.z = abs_view_pos.z - scenery.center.z;
fgPrintf( FG_VIEW, FG_DEBUG, "Absolute view pos = %.4f, %.4f, %.4f\n",
abs_view_pos.x, abs_view_pos.y, abs_view_pos.z);
fgPrintf( FG_VIEW, FG_DEBUG, "Relative view pos = %.4f, %.4f, %.4f\n",
view_pos.x, view_pos.y, view_pos.z);
// Derive the LOCAL aircraft rotation matrix (roll, pitch, yaw)
// from FG_T_local_to_body[3][3]
// Question: Why is the LaRCsim matrix arranged so differently
// than the one we need???
LOCAL[0][0] = FG_T_local_to_body_33;
LOCAL[0][1] = -FG_T_local_to_body_32;
LOCAL[0][2] = -FG_T_local_to_body_31;
LOCAL[0][3] = 0.0;
LOCAL[1][0] = -FG_T_local_to_body_23;
LOCAL[1][1] = FG_T_local_to_body_22;
LOCAL[1][2] = FG_T_local_to_body_21;
LOCAL[1][3] = 0.0;
LOCAL[2][0] = -FG_T_local_to_body_13;
LOCAL[2][1] = FG_T_local_to_body_12;
LOCAL[2][2] = FG_T_local_to_body_11;
LOCAL[2][3] = 0.0;
LOCAL[3][0] = LOCAL[3][1] = LOCAL[3][2] = LOCAL[3][3] = 0.0;
LOCAL[3][3] = 1.0;
// printf("LaRCsim LOCAL matrix\n");
// MAT3print(LOCAL, stdout);
#ifdef OLD_LOCAL_TO_BODY_CODE
// old code to calculate LOCAL matrix calculated from Phi,
// Theta, and Psi (roll, pitch, yaw)
MAT3_SET_VEC(vec, 0.0, 0.0, 1.0);
MAT3rotate(R, vec, FG_Phi);
/* printf("Roll matrix\n"); */
/* MAT3print(R, stdout); */
MAT3_SET_VEC(vec, 0.0, 1.0, 0.0);
/* MAT3mult_vec(vec, vec, R); */
MAT3rotate(TMP, vec, FG_Theta);
/* printf("Pitch matrix\n"); */
/* MAT3print(TMP, stdout); */
MAT3mult(R, R, TMP);
MAT3_SET_VEC(vec, 1.0, 0.0, 0.0);
/* MAT3mult_vec(vec, vec, R); */
/* MAT3rotate(TMP, vec, FG_Psi - FG_PI_2); */
MAT3rotate(TMP, vec, -FG_Psi);
/* printf("Yaw matrix\n");
MAT3print(TMP, stdout); */
MAT3mult(LOCAL, R, TMP);
// printf("FG derived LOCAL matrix\n");
// MAT3print(LOCAL, stdout);
#endif // OLD_LOCAL_TO_BODY_CODE
// Derive the local UP transformation matrix based on *geodetic*
// coordinates
MAT3_SET_VEC(vec, 0.0, 0.0, 1.0);
MAT3rotate(R, vec, FG_Longitude); // R = rotate about Z axis
// printf("Longitude matrix\n");
// MAT3print(R, stdout);
MAT3_SET_VEC(vec, 0.0, 1.0, 0.0);
MAT3mult_vec(vec, vec, R);
MAT3rotate(TMP, vec, -FG_Latitude); // TMP = rotate about X axis
// printf("Latitude matrix\n");
// MAT3print(TMP, stdout);
MAT3mult(UP, R, TMP);
// printf("Local up matrix\n");
// MAT3print(UP, stdout);
MAT3_SET_VEC(local_up, 1.0, 0.0, 0.0);
MAT3mult_vec(local_up, local_up, UP);
// printf( "Local Up = (%.4f, %.4f, %.4f)\n",
// local_up[0], local_up[1], local_up[2]);
// Alternative method to Derive local up vector based on
// *geodetic* coordinates
// alt_up = fgPolarToCart(FG_Longitude, FG_Latitude, 1.0);
// printf( " Alt Up = (%.4f, %.4f, %.4f)\n",
// alt_up.x, alt_up.y, alt_up.z);
// Calculate the VIEW matrix
MAT3mult(VIEW, LOCAL, UP);
// printf("VIEW matrix\n");
// MAT3print(VIEW, stdout);
// generate the current up, forward, and fwrd-view vectors
MAT3_SET_VEC(vec, 1.0, 0.0, 0.0);
MAT3mult_vec(view_up, vec, VIEW);
MAT3_SET_VEC(vec, 0.0, 0.0, 1.0);
MAT3mult_vec(forward, vec, VIEW);
// printf( "Forward vector is (%.2f,%.2f,%.2f)\n", forward[0], forward[1],
// forward[2]);
MAT3rotate(TMP, view_up, view_offset);
MAT3mult_vec(view_forward, forward, TMP);
// make a vector to the current view position
MAT3_SET_VEC(v0, view_pos.x, view_pos.y, view_pos.z);
// Given a vector pointing straight down (-Z), map into onto the
// local plane representing "horizontal". This should give us the
// local direction for moving "south".
MAT3_SET_VEC(minus_z, 0.0, 0.0, -1.0);
map_vec_onto_cur_surface_plane(local_up, v0, minus_z, surface_south);
MAT3_NORMALIZE_VEC(surface_south, ntmp);
// printf( "Surface direction directly south %.2f %.2f %.2f\n",
// surface_south[0], surface_south[1], surface_south[2]);
// now calculate the surface east vector
MAT3rotate(TMP, view_up, FG_PI_2);
MAT3mult_vec(surface_east, surface_south, TMP);
// printf( "Surface direction directly east %.2f %.2f %.2f\n",
// surface_east[0], surface_east[1], surface_east[2]);
// printf( "Should be close to zero = %.2f\n",
// MAT3_DOT_PRODUCT(surface_south, surface_east));
}
// Update the "World to Eye" transformation matrix
// This is most useful for view frustum culling
void fgVIEW::UpdateWorldToEye( fgFLIGHT *f ) {
MAT3mat R_Phi, R_Theta, R_Psi, R_Lat, R_Lon, T_view;
MAT3mat TMP;
MAT3hvec vec;
// if we have a view offset use slow way for now
if(fabs(view_offset)>FG_EPSILON){
// Roll Matrix
MAT3_SET_HVEC(vec, 0.0, 0.0, -1.0, 1.0);
MAT3rotate(R_Phi, vec, FG_Phi);
// printf("Roll matrix (Phi)\n");
// MAT3print(R_Phi, stdout);
// Pitch Matrix
MAT3_SET_HVEC(vec, 1.0, 0.0, 0.0, 1.0);
MAT3rotate(R_Theta, vec, FG_Theta);
// printf("\nPitch matrix (Theta)\n");
// MAT3print(R_Theta, stdout);
// Yaw Matrix
MAT3_SET_HVEC(vec, 0.0, -1.0, 0.0, 1.0);
MAT3rotate(R_Psi, vec, FG_Psi + FG_PI - view_offset );
// printf("\nYaw matrix (Psi)\n");
// MAT3print(R_Psi, stdout);
// aircraft roll/pitch/yaw
MAT3mult(TMP, R_Phi, R_Theta);
MAT3mult(AIRCRAFT, TMP, R_Psi);
} else { // JUST USE LOCAL_TO_BODY NHV 5/25/98
// hey this is even different then LOCAL[][] above ??
AIRCRAFT[0][0] = -FG_T_local_to_body_22;
AIRCRAFT[0][1] = -FG_T_local_to_body_23;
AIRCRAFT[0][2] = FG_T_local_to_body_21;
AIRCRAFT[0][3] = 0.0;
AIRCRAFT[1][0] = FG_T_local_to_body_32;
AIRCRAFT[1][1] = FG_T_local_to_body_33;
AIRCRAFT[1][2] = -FG_T_local_to_body_31;
AIRCRAFT[1][3] = 0.0;
AIRCRAFT[2][0] = FG_T_local_to_body_12;
AIRCRAFT[2][1] = FG_T_local_to_body_13;
AIRCRAFT[2][2] = -FG_T_local_to_body_11;
AIRCRAFT[2][3] = 0.0;
AIRCRAFT[3][0] = AIRCRAFT[3][1] = AIRCRAFT[3][2] = AIRCRAFT[3][3] = 0.0;
AIRCRAFT[3][3] = 1.0;
// ??? SOMETHING LIKE THIS SHOULD WORK NHV
// Rotate about LOCAL_UP (AIRCRAFT[2][])
// MAT3_SET_HVEC(vec, AIRCRAFT[2][0], AIRCRAFT[2][1],
// AIRCRAFT[2][2], AIRCRAFT[2][3]);
// MAT3rotate(TMP, vec, FG_PI - view_offset );
// MAT3mult(AIRCRAFT, AIRCRAFT, TMP);
}
// printf("\naircraft roll pitch yaw\n");
// MAT3print(AIRCRAFT, stdout);
// View position in scenery centered coordinates
MAT3_SET_HVEC(vec, view_pos.x, view_pos.y, view_pos.z, 1.0);
MAT3translate(T_view, vec);
// printf("\nTranslation matrix\n");
// MAT3print(T_view, stdout);
// Latitude
MAT3_SET_HVEC(vec, 1.0, 0.0, 0.0, 1.0);
// R_Lat = rotate about X axis
MAT3rotate(R_Lat, vec, FG_Latitude);
// printf("\nLatitude matrix\n");
// MAT3print(R_Lat, stdout);
// Longitude
MAT3_SET_HVEC(vec, 0.0, 0.0, 1.0, 1.0);
// R_Lon = rotate about Z axis
MAT3rotate(R_Lon, vec, FG_Longitude - FG_PI_2 );
// printf("\nLongitude matrix\n");
// MAT3print(R_Lon, stdout);
#ifdef THIS_IS_OLD_CODE
// View position in scenery centered coordinates
MAT3_SET_HVEC(vec, view_pos.x, view_pos.y, view_pos.z, 1.0);
MAT3translate(T_view, vec);
// printf("\nTranslation matrix\n");
// MAT3print(T_view, stdout);
// aircraft roll/pitch/yaw
MAT3mult(TMP, R_Phi, R_Theta);
MAT3mult(AIRCRAFT, TMP, R_Psi);
// printf("\naircraft roll pitch yaw\n");
// MAT3print(AIRCRAFT, stdout);
#endif THIS_IS_OLD_CODE
// lon/lat
MAT3mult(WORLD, R_Lat, R_Lon);
// printf("\nworld\n");
// MAT3print(WORLD, stdout);
MAT3mult(EYE_TO_WORLD, AIRCRAFT, WORLD);
MAT3mult(EYE_TO_WORLD, EYE_TO_WORLD, T_view);
// printf("\nEye to world\n");
// MAT3print(EYE_TO_WORLD, stdout);
MAT3invert(WORLD_TO_EYE, EYE_TO_WORLD);
// printf("\nWorld to eye\n");
// MAT3print(WORLD_TO_EYE, stdout);
// printf( "\nview_pos = %.2f %.2f %.2f\n",
// view_pos.x, view_pos.y, view_pos.z );
// MAT3_SET_HVEC(eye, 0.0, 0.0, 0.0, 1.0);
// MAT3mult_vec(vec, eye, EYE_TO_WORLD);
// printf("\neye -> world = %.2f %.2f %.2f\n", vec[0], vec[1], vec[2]);
// MAT3_SET_HVEC(vec1, view_pos.x, view_pos.y, view_pos.z, 1.0);
// MAT3mult_vec(vec, vec1, WORLD_TO_EYE);
// printf( "\nabs_view_pos -> eye = %.2f %.2f %.2f\n",
// vec[0], vec[1], vec[2]);
}
// Destructor
fgVIEW::~fgVIEW( void ) {
}
// Basically, this is a modified version of the Mesa gluLookAt()
// function that's been modified slightly so we can capture the result
// before sending it off to OpenGL land.
void fg_gluLookAt( GLdouble eyex, GLdouble eyey, GLdouble eyez,
GLdouble centerx, GLdouble centery, GLdouble centerz,
GLdouble upx, GLdouble upy, GLdouble upz )
{
GLdouble *m;
GLdouble x[3], y[3], z[3];
GLdouble mag;
m = current_view.MODEL_VIEW;
/* Make rotation matrix */
/* Z vector */
z[0] = eyex - centerx;
z[1] = eyey - centery;
z[2] = eyez - centerz;
mag = sqrt( z[0]*z[0] + z[1]*z[1] + z[2]*z[2] );
if (mag) { /* mpichler, 19950515 */
z[0] /= mag;
z[1] /= mag;
z[2] /= mag;
}
/* Y vector */
y[0] = upx;
y[1] = upy;
y[2] = upz;
/* X vector = Y cross Z */
x[0] = y[1]*z[2] - y[2]*z[1];
x[1] = -y[0]*z[2] + y[2]*z[0];
x[2] = y[0]*z[1] - y[1]*z[0];
/* Recompute Y = Z cross X */
y[0] = z[1]*x[2] - z[2]*x[1];
y[1] = -z[0]*x[2] + z[2]*x[0];
y[2] = z[0]*x[1] - z[1]*x[0];
/* mpichler, 19950515 */
/* cross product gives area of parallelogram, which is < 1.0 for
* non-perpendicular unit-length vectors; so normalize x, y here
*/
mag = sqrt( x[0]*x[0] + x[1]*x[1] + x[2]*x[2] );
if (mag) {
x[0] /= mag;
x[1] /= mag;
x[2] /= mag;
}
mag = sqrt( y[0]*y[0] + y[1]*y[1] + y[2]*y[2] );
if (mag) {
y[0] /= mag;
y[1] /= mag;
y[2] /= mag;
}
#define M(row,col) m[col*4+row]
M(0,0) = x[0]; M(0,1) = x[1]; M(0,2) = x[2]; M(0,3) = 0.0;
M(1,0) = y[0]; M(1,1) = y[1]; M(1,2) = y[2]; M(1,3) = 0.0;
M(2,0) = z[0]; M(2,1) = z[1]; M(2,2) = z[2]; M(2,3) = 0.0;
M(3,0) = 0.0; M(3,1) = 0.0; M(3,2) = 0.0; M(3,3) = 1.0;
#undef M
// Translate Eye to Origin
// replaces: glTranslated( -eyex, -eyey, -eyez );
m[12] = m[0] * -eyex + m[4] * -eyey + m[8] * -eyez + m[12];
m[13] = m[1] * -eyex + m[5] * -eyey + m[9] * -eyez + m[13];
m[14] = m[2] * -eyex + m[6] * -eyey + m[10] * -eyez + m[14];
m[15] = m[3] * -eyex + m[7] * -eyey + m[11] * -eyez + m[15];
// xglMultMatrixd( m );
xglLoadMatrixd( m );
}
// $Log$
// Revision 1.15 1998/07/12 03:14:43 curt
// Added ground collision detection.
// Did some serious horsing around to be able to "hug" the ground properly
// and still be able to take off.
// Set the near clip plane to 1.0 meters when less than 10 meters above the
// ground.
// Did some serious horsing around getting the initial airplane position to be
// correct based on rendered terrain elevation.
// Added a little cheat/hack that will prevent the view position from ever
// dropping below the terrain, even when the flight model doesn't quite
// put you as high as you'd like.
//
// Revision 1.14 1998/07/08 14:45:08 curt
// polar3d.h renamed to polar3d.hxx
// vector.h renamed to vector.hxx
// updated audio support so it waits to create audio classes (and tie up
// /dev/dsp) until the mpg123 player is finished.
//
// Revision 1.13 1998/07/04 00:52:27 curt
// Add my own version of gluLookAt() (which is nearly identical to the
// Mesa/glu version.) But, by calculating the Model View matrix our selves
// we can save this matrix without having to read it back in from the video
// card. This hopefully allows us to save a few cpu cycles when rendering
// out the fragments because we can just use glLoadMatrixd() with the
// precalculated matrix for each tile rather than doing a push(), translate(),
// pop() for every fragment.
//
// Panel status defaults to off for now until it gets a bit more developed.
//
// Extract OpenGL driver info on initialization.
//
// Revision 1.12 1998/06/03 00:47:15 curt
// Updated to compile in audio support if OSS available.
// Updated for new version of Steve's audio library.
// STL includes don't use .h
// Small view optimizations.
//
// Revision 1.11 1998/05/27 02:24:05 curt
// View optimizations by Norman Vine.
//
// Revision 1.10 1998/05/17 16:59:03 curt
// First pass at view frustum culling now operational.
//
// Revision 1.9 1998/05/16 13:08:37 curt
// C++ - ified views.[ch]xx
// Shuffled some additional view parameters into the fgVIEW class.
// Changed tile-radius to tile-diameter because it is a much better
// name.
// Added a WORLD_TO_EYE transformation to views.cxx. This allows us
// to transform world space to eye space for view frustum culling.
//
// Revision 1.8 1998/05/02 01:51:01 curt
// Updated polartocart conversion routine.
//
// Revision 1.7 1998/04/30 12:34:20 curt
// Added command line rendering options:
// enable/disable fog/haze
// specify smooth/flat shading
// disable sky blending and just use a solid color
// enable wireframe drawing mode
//
// Revision 1.6 1998/04/28 01:20:23 curt
// Type-ified fgTIME and fgVIEW.
// Added a command line option to disable textures.
//
// Revision 1.5 1998/04/26 05:10:04 curt
// "struct fgLIGHT" -> "fgLIGHT" because fgLIGHT is typedef'd.
//
// Revision 1.4 1998/04/25 22:04:53 curt
// Use already calculated LaRCsim values to create the roll/pitch/yaw
// transformation matrix (we call it LOCAL)
//
// Revision 1.3 1998/04/25 20:24:02 curt
// Cleaned up initialization sequence to eliminate interdependencies
// between sun position, lighting, and view position. This creates a
// valid single pass initialization path.
//
// Revision 1.2 1998/04/24 00:49:22 curt
// Wrapped "#include <config.h>" in "#ifdef HAVE_CONFIG_H"
// Trying out some different option parsing code.
// Some code reorganization.
//
// Revision 1.1 1998/04/22 13:25:45 curt
// C++ - ifing the code.
// Starting a bit of reorganization of lighting code.
//
// Revision 1.16 1998/04/18 04:11:29 curt
// Moved fg_debug to it's own library, added zlib support.
//
// Revision 1.15 1998/02/20 00:16:24 curt
// Thursday's tweaks.
//
// Revision 1.14 1998/02/09 15:07:50 curt
// Minor tweaks.
//
// Revision 1.13 1998/02/07 15:29:45 curt
// Incorporated HUD changes and struct/typedef changes from Charlie Hotchkiss
// <chotchkiss@namg.us.anritsu.com>
//
// Revision 1.12 1998/01/29 00:50:28 curt
// Added a view record field for absolute x, y, z position.
//
// Revision 1.11 1998/01/27 00:47:58 curt
// Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
// system and commandline/config file processing code.
//
// Revision 1.10 1998/01/19 19:27:09 curt
// Merged in make system changes from Bob Kuehne <rpk@sgi.com>
// This should simplify things tremendously.
//
// Revision 1.9 1998/01/13 00:23:09 curt
// Initial changes to support loading and management of scenery tiles. Note,
// there's still a fair amount of work left to be done.
//
// Revision 1.8 1997/12/30 22:22:33 curt
// Further integration of event manager.
//
// Revision 1.7 1997/12/30 20:47:45 curt
// Integrated new event manager with subsystem initializations.
//
// Revision 1.6 1997/12/22 04:14:32 curt
// Aligned sky with sun so dusk/dawn effects can be correct relative to the sun.
//
// Revision 1.5 1997/12/18 04:07:02 curt
// Worked on properly translating and positioning the sky dome.
//
// Revision 1.4 1997/12/17 23:13:36 curt
// Began working on rendering a sky.
//
// Revision 1.3 1997/12/15 23:54:50 curt
// Add xgl wrappers for debugging.
// Generate terrain normals on the fly.
//
// Revision 1.2 1997/12/10 22:37:48 curt
// Prepended "fg" on the name of all global structures that didn't have it yet.
// i.e. "struct WEATHER {}" became "struct fgWEATHER {}"
//
// Revision 1.1 1997/08/27 21:31:17 curt
// Initial revision.
//