[Flightgear-devel] Runway HUD projection

Aaron Wilson Mon, 08 Nov 2004 13:12:53 -0800

I'm trying to project a virtual runway image on the HUD and I do not fully understand the FlightGear coordinate system. I am using the following code to get the four corners on the runway and seem to correspond to the absolute_view_pos vector when located on the corner of the runway. I am trying to render spheres on the corners of the runway to be sure that the XYZ coordinates of the runway corners are correct, but the spheres are not being displayed. I feel that the model view and/or the projection matrix may be incorrect since I am trying to render the spheres inside the HUD instrument draw() function.

void runway_instr::get_rwy_points(sgdVec3 *corners) {
Point3D center = globals->get_scenery()->get_center();

double alt = current_aircraft.fdm_state->get_Runway_altitude()*SG_FEET_TO_METER;

double length = (runway.length/2.0)*SG_FEET_TO_METER;

double width = (runway.width/2.0)*SG_FEET_TO_METER;

double frontLat,frontLon,backLat,backLon,az,tempLat,tempLon;

geo_direct_wgs_84(alt,runway.lat,runway.lon,runway.heading,length,&backLat,&backLon,&az);
geo_direct_wgs_84(alt,runway.lat,runway.lon,runway.heading+180,length,&frontLat,&frontLon,&az);

        geo_direct_wgs_84(alt,backLat,backLon,runway.heading+90,width,&tempLat,&tempLon,&az);
        sgGeodToCart(tempLat*SG_DEGREES_TO_RADIANS,tempLon*SG_DEGREES_TO_RADIANS,alt,corners[0]);

        geo_direct_wgs_84(alt,backLat,backLon,runway.heading-90,width,&tempLat,&tempLon,&az);
        sgGeodToCart(tempLat*SG_DEGREES_TO_RADIANS,tempLon*SG_DEGREES_TO_RADIANS,alt,corners[1]);

        geo_direct_wgs_84(alt,frontLat,frontLon,runway.heading-90,width,&tempLat,&tempLon,&az);
        sgGeodToCart(tempLat*SG_DEGREES_TO_RADIANS,tempLon*SG_DEGREES_TO_RADIANS,alt,corners[2]);

        geo_direct_wgs_84(alt,frontLat,frontLon,runway.heading+90,width,&tempLat,&tempLon,&az);
        sgGeodToCart(tempLat*SG_DEGREES_TO_RADIANS,tempLon*SG_DEGREES_TO_RADIANS,alt,corners[3]);
}

void runway_instr::draw() {
         runway = get_active_runway();
         get_rwy_points(rwy_corners);
         FGViewer* view = globals->get_current_view();

double * viewPos = view->get_absolute_view_pos();

const sgVec4 *viewVec = view->get_VIEW();

        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();

        glLoadMatrixf( (float *)viewVec );

        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();

        GLUquadricObj *quad = gluNewQuadric();

for(int c=0; c<4; c++) {

glTranslatef(rwy_corners[c][0],rwy_corners[c][1],rwy_corners[c][2]);

gluSphere(quad,100.0,50,50);

        glTranslatef(-rwy_corners[c][0],-rwy_corners[c][1],-rwy_corners[c][2]);
        }
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
}

Aaron I. Wilson
AST: Computer Engineer
TEL: (304) 367-8299
FAX: (304) 367-8203
[EMAIL PROTECTED]
http://www.ivv.nasa.gov/

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[Flightgear-devel] Runway HUD projection

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