First stab at code to build a nurbs surface that approximates the surface
of an airport.
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206
src/Airports/GenAirports/apt_surface.cxx
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206
src/Airports/GenAirports/apt_surface.cxx
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// apt_surface.cxx -- class to manage airport terrain surface
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// approximation and smoothing
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//
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// Written by Curtis Olson, started March 2003.
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//
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// Copyright (C) 2003 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 modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (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,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU 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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//
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#include <nurbs++/nurbsS.hh>
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#include <nurbs++/nurbsSub.hh>
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#include <simgear/constants.h>
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#include <simgear/math/sg_types.hxx>
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#include <Array/array.hxx>
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#include "apt_surface.hxx"
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SG_USING_NAMESPACE( PLib );
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// fix node elevations. Offset is added to the final elevation
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static void calc_elevations( const string &root, Matrix_Point3Df &Pts ) {
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string_list elev_src;
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elev_src.clear();
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elev_src.push_back( "SRTM-1" );
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elev_src.push_back( "SRTM-3" );
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elev_src.push_back( "DEM-3" );
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elev_src.push_back( "DEM-30" );
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bool done = false;
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int i, j;
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TGArray array;
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// just bail if no work to do
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if ( Pts.rows() == 0 || Pts.cols() == 0 ) {
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return;
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}
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// set all elevations to -9999
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for ( i = 0; i < Pts.rows(); ++i ) {
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for ( j = 0; j < Pts.cols(); ++j ) {
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Point3Df p = Pts(i,j);
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p.z() = -9999.0;
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}
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}
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while ( !done ) {
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// find first node with -9999 elevation
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Point3Df first;
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bool found_one = false;
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for ( i = 0; i < Pts.rows(); ++i ) {
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for ( j = 0; j < Pts.cols(); ++j ) {
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Point3Df p = Pts(i,j);
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if ( p.z() < -9000.0 && !found_one ) {
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first = p;
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found_one = true;
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}
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}
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}
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if ( found_one ) {
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SGBucket b( first.x(), first.y() );
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string base = b.gen_base_path();
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// try the various elevation sources
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j = 0;
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bool found_file = false;
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while ( !found_file && j < (int)elev_src.size() ) {
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string array_path = root + "/" + elev_src[j] + "/" + base
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+ "/" + b.gen_index_str() + ".arr";
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if ( array.open(array_path) ) {
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found_file = true;
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cout << "Using array_path = " << array_path << endl;
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}
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j++;
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}
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// this will fill in a zero structure if no array data
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// found/opened
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array.parse( b );
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// update all the non-updated elevations that are inside
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// this array file
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double elev;
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done = true;
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for ( i = 0; i < Pts.rows(); ++i ) {
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for ( j = 0; j < Pts.cols(); ++j ) {
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Point3Df p = Pts(i,j);
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if ( p.z() < -9000.0 ) {
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done = false;
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elev = array.interpolate_altitude( p.x() * 3600.0,
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p.y() * 3600.0 );
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if ( elev > -9000 ) {
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p.z() = elev;
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Pts(i,j) = p;
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cout << "interpolating for " << p << endl;
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}
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}
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}
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}
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array.close();
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} else {
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done = true;
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}
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}
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}
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// Constructor, specify min and max coordinates of desired area in
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// lon/lat degrees
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TGAptSurface::TGAptSurface( const string& path,
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Point3D _min_deg, Point3D _max_deg )
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{
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// Calculate desired size of grid
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min_deg = _min_deg;
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max_deg = _max_deg;
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// The following size calculations are for the purpose of
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// determining grid divisions so it's not important that they be
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// *exact*, just ball park.
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double y_deg = max_deg.lat() - min_deg.lat();
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double y_rad = y_deg * SG_DEGREES_TO_RADIANS;
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double y_nm = y_rad * SG_RAD_TO_NM;
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double y_m = y_nm * SG_NM_TO_METER;
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double xfact = cos( min_deg.lat() * SG_DEGREES_TO_RADIANS );
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double x_deg = max_deg.lon() - min_deg.lon();
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double x_rad = x_deg * SG_DEGREES_TO_RADIANS;
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double x_nm = x_rad * SG_RAD_TO_NM * xfact;
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double x_m = x_nm * SG_NM_TO_METER;
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cout << "Area size = " << x_m << " x " << y_m << " (m)" << endl;
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int xdivs = (int)(x_m / 400.0) + 1;
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int ydivs = (int)(y_m / 400.0) + 1;
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// Build the input grid
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cout << " M(" << xdivs << "," << ydivs << ")" << endl;
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Matrix_Point3Df Pts(xdivs, ydivs);
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double dlon = x_deg / xdivs;
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double dlat = y_deg / ydivs;
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for ( int i = 0; i < xdivs; ++i ) {
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for ( int j = 0; j < ydivs; ++j ) {
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Pts(i,j) = Point3Df( min_deg.lon() + i * dlon,
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min_deg.lat() + j * dlat,
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-9999 );
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}
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}
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// Determine elevation of the grid points
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calc_elevations( path, Pts );
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// Create the nurbs surface
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apt_surf = new PlNurbsSurfacef;
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apt_surf->globalInterp( Pts, 3, 3);
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}
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TGAptSurface::~TGAptSurface() {
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delete apt_surf;
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}
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// Query the elevation of a point, return -9999 if out of range
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double TGAptSurface::query( double lon_deg, double lat_deg ) {
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// sanity check
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if ( lon_deg < min_deg.lon() || lon_deg > max_deg.lon() ||
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lat_deg < min_deg.lat() || lat_deg > max_deg.lat() )
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{
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cout << "Warning: query out of bounds for NURBS surface!" << endl;
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return -9999.0;
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}
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// convert lon,lat to nurbs space
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double x = (lon_deg - min_deg.lon()) / (max_deg.lon() - min_deg.lon());
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double y = (lat_deg - min_deg.lat()) / (max_deg.lat() - min_deg.lat());
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cout << " querying for " << x << ", " << y << " = ";
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Point3Df p = apt_surf->pointAt( x, y );
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cout << p.z() << endl;
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return p.z();
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}
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74
src/Airports/GenAirports/apt_surface.hxx
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74
src/Airports/GenAirports/apt_surface.hxx
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@ -0,0 +1,74 @@
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// apt_surface.hxx -- class to manage airport terrain surface
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// approximation and smoothing
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//
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// Written by Curtis Olson, started March 2003.
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//
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// Copyright (C) 2003 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 modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (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,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU 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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//
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#ifndef _APT_SURFACE_HXX
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#define _APT_SURFACE_HXX
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#include <string>
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#include <nurbs++/nurbsS.hh>
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#include <simgear/math/point3d.hxx>
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/***
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* Note of explanation. When a TGAptSurface instance is created, you
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* must specify a min and max lon/lat containing the entire airport
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* area. The class will divide up that area into a reasonably sized
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* regular grid. It will then look up the elevation of each point on
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* the grid from the DEM/Array data. Finally it will build a nurbs
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* surface from this grid. Each vertex of the actual airport model is
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* drapped over this nurbs surface rather than over the underlying
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* terrain data. This provides a) smoothing of noisy terrain data, b)
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* natural rises and dips in the airport surface, c) chance to impress
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* colleages by using something or other nurbs surfaces -- or whatever
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* they are called. :-)
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*/
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class TGAptSurface {
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private:
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// The actual nurbs surface approximation for the airport
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PlNurbsSurfacef *apt_surf;
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Point3D min_deg, max_deg;
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public:
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// Constructor, specify min and max coordinates of desired area in
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// lon/lat degrees
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TGAptSurface( const string &path, Point3D _min_deg, Point3D _max_deg );
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// Destructor
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~TGAptSurface();
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// Query the elevation of a point, return -9999 if out of range
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double query( double lon_deg, double lat_deg );
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};
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#endif // _APT_SURFACE_HXX
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