From 8aa30c3d3059fcff139d5a25d7488f68f24735e5 Mon Sep 17 00:00:00 2001
From: curt <curt>
Date: Wed, 11 Nov 1998 00:24:00 +0000
Subject: [PATCH] Added Michael Johnson's audio patches for testing. Also did a
 few tweaks to avoid numerical problems when starting at a place with no (or
 bogus) scenery.

---
 Main/GLUTmain.cxx | 66 ++++++++++++++++++++++++++++++++++++++++++++---
 Main/fg_init.cxx  |  9 +++++++
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/Main/GLUTmain.cxx b/Main/GLUTmain.cxx
index 4de2b3ad0..562753a99 100644
--- a/Main/GLUTmain.cxx
+++ b/Main/GLUTmain.cxx
@@ -21,6 +21,7 @@
 // $Id$
 // (Log is kept at end of this file)
 
+#define MICHAEL_JOHNSON_EXPERIMENTAL_ENGINE_AUDIO
 
 #ifdef HAVE_CONFIG_H
 #  include <config.h>
@@ -572,10 +573,64 @@ static void fgMainLoop( void ) {
     // Run audio scheduler
 #ifdef ENABLE_AUDIO_SUPPORT
     if ( current_options.get_sound() && audio_sched->working() ) {
-	double param = controls.get_throttle( 0 ) * 2.0 + 1.0;
 
-	pitch_envelope.setStep  ( 0, 0.01, param );
-	volume_envelope.setStep ( 0, 0.01, param );
+#   ifdef MICHAEL_JOHNSON_EXPERIMENTAL_ENGINE_AUDIO
+
+	// note: all these factors are relative to the sample.  our
+	// sample format should really contain a conversion factor so
+	// that we can get prop speed right for arbitrary samples.
+	// Note that for normal-size props, there is a point at which
+	// the prop tips approach the speed of sound; that is a pretty
+	// strong limit to how fast the prop can go.
+
+	// multiplication factor is prime pitch control; add some log
+	// component for verisimilitude
+
+	double pitch = log((controls.get_throttle(0) * 14.0) + 1.0);
+	//fprintf(stderr, "pitch1: %f ", pitch);
+	if (controls.get_throttle(0) > 0.0 || f->v_rel_wind > 40.0) {
+	    //fprintf(stderr, "rel_wind: %f ", f->v_rel_wind);
+	    // only add relative wind and AoA if prop is moving
+	    // or we're really flying at idle throttle
+	    if (pitch < 5.4) {  // this needs tuning
+		// prop tips not breaking sound barrier
+		pitch += log(f->v_rel_wind + 0.8)/2;
+	    } else {
+		// prop tips breaking sound barrier
+		pitch += log(f->v_rel_wind + 0.8)/10;
+	    }
+	    //fprintf(stderr, "pitch2: %f ", pitch);
+	    //fprintf(stderr, "AoA: %f ", FG_Gamma_vert_rad);
+
+	    // Angle of Attack next... -x^3(e^x) is my best guess Just
+	    // need to calculate some reasonable scaling factor and
+	    // then clamp it on the positive aoa (neg adj) side
+	    double aoa = FG_Gamma_vert_rad * 2.2;
+	    double aoa_adj = pow(-aoa, 3) * pow(M_E, aoa);
+	    if (aoa_adj < -0.8) aoa_adj = -0.8;
+	    pitch += aoa_adj;
+	    //fprintf(stderr, "pitch3: %f ", pitch);
+
+	    // don't run at absurdly slow rates -- not realistic
+	    // and sounds bad to boot.  :-)
+	    if (pitch < 0.8) pitch = 0.8;
+	}
+	//fprintf(stderr, "pitch4: %f\n", pitch);
+
+	double volume = controls.get_throttle(0) * 1.15 + 0.3 +
+	    log(f->v_rel_wind + 1.0)/14.0;
+	// fprintf(stderr, "volume: %f\n", volume);
+
+	pitch_envelope.setStep  ( 0, 0.01, pitch );
+	volume_envelope.setStep ( 0, 0.01, volume );
+
+#   else
+
+       double param = controls.get_throttle( 0 ) * 2.0 + 1.0;
+       pitch_envelope.setStep  ( 0, 0.01, param );
+       volume_envelope.setStep ( 0, 0.01, param );
+
+#   endif // experimental throttle patch
 
 	audio_sched -> update();
     }
@@ -891,6 +946,11 @@ int main( int argc, char **argv ) {
 
 
 // $Log$
+// Revision 1.66  1998/11/11 00:24:00  curt
+// Added Michael Johnson's audio patches for testing.
+// Also did a few tweaks to avoid numerical problems when starting at a place
+// with no (or bogus) scenery.
+//
 // Revision 1.65  1998/11/09 23:39:22  curt
 // Tweaks for the instrument panel.
 //
diff --git a/Main/fg_init.cxx b/Main/fg_init.cxx
index 7d4f2f205..e9c090669 100644
--- a/Main/fg_init.cxx
+++ b/Main/fg_init.cxx
@@ -212,8 +212,12 @@ int fgInitSubsystems( void )
     abs_view_pos = fgGeodToCart(geod_pos);
 
     // Calculate ground elevation at starting point
+    FG_LOG( FG_GENERAL, FG_DEBUG, 
+	    "Altitude before update " << scenery.cur_elev );
     scenery.cur_elev = 
 	fgTileMgrCurElev( FG_Longitude, FG_Latitude, abs_view_pos );
+    FG_LOG( FG_GENERAL, FG_DEBUG, 
+	    "Altitude after update " << scenery.cur_elev );
     FG_Runway_altitude = scenery.cur_elev * METER_TO_FEET;
 
     // Reset our altitude if we are below ground
@@ -377,6 +381,11 @@ int fgInitSubsystems( void )
 
 
 // $Log$
+// Revision 1.49  1998/11/11 00:24:02  curt
+// Added Michael Johnson's audio patches for testing.
+// Also did a few tweaks to avoid numerical problems when starting at a place
+// with no (or bogus) scenery.
+//
 // Revision 1.48  1998/11/07 19:07:10  curt
 // Enable release builds using the --without-logging option to the configure
 // script.  Also a couple log message cleanups, plus some C to C++ comment
-- 
2.39.2