TITANIC: Simulate sound distances by reducing volume

2 files changed, 52 insertions, 7 deletions

diff --git a/engines/titanic/sound/qmixer.cpp b/engines/titanic/sound/qmixer.cpp
index f05f8c3ab9..ecc0bbcba4 100644
--- a/engines/titanic/sound/qmixer.cpp
+++ b/engines/titanic/sound/qmixer.cpp
@@ -88,11 +88,28 @@ void QMixer::qsWaveMixSetVolume(int iChannel, uint flags, uint volume) {
 }
 
 void QMixer::qsWaveMixSetSourcePosition(int iChannel, uint flags, const QSVECTOR &position) {
-	// Not currently implemented in ScummVM
+	ChannelEntry &channel = _channels[iChannel];
+
+	// Flag whether distance should reset when a new sound is started
+	channel._resetDistance = (flags & QMIX_USEONCE) != 0;
+
+	// Currently, we only do a basic simulation of spatial positioning by
+	// getting the distance, and proportionately reducing the volume the
+	// further away the source is
+	channel._distance = sqrt(position.x * position.x + position.y * position.y
+		+ position.z * position.z);
 }
 
 void QMixer::qsWaveMixSetPolarPosition(int iChannel, uint flags, const QSPOLAR &position) {
-	// Not currently implemented in ScummVM
+	ChannelEntry &channel = _channels[iChannel];
+
+	// Flag whether distance should reset when a new sound is started
+	channel._resetDistance = (flags & QMIX_USEONCE) != 0;
+
+	// Currently, we only do a basic simulation of spatial positioning by
+	// getting the distance, and proportionately reducing the volume the
+	// further away the source is
+	channel._distance = position.range;
 }
 
 void QMixer::qsWaveMixSetListenerPosition(const QSVECTOR &position, uint flags) {
@@ -168,7 +185,8 @@ void QMixer::qsWaveMixPump() {
 
 			if (channel._volume != oldVolume && !channel._sounds.empty()
 					&& channel._sounds.front()._started) {
-				_mixer->setChannelVolume(channel._sounds.front()._soundHandle, channel._volume);
+				_mixer->setChannelVolume(channel._sounds.front()._soundHandle,
+					channel.getRawVolume());
 			}
 		}
 
@@ -182,7 +200,7 @@ void QMixer::qsWaveMixPump() {
 					sound._waveFile->_stream->rewind();
 					_mixer->playStream(sound._waveFile->_soundType,
 						&sound._soundHandle, sound._waveFile->_stream,
-						-1, channel._volume, 0, DisposeAfterUse::NO);
+						-1, channel.getRawVolume(), 0, DisposeAfterUse::NO);
 				} else {
 					// Sound is finished
 					if (sound._callback)
@@ -200,13 +218,30 @@ void QMixer::qsWaveMixPump() {
 		if (!channel._sounds.empty()) {
 			SoundEntry &sound = channel._sounds.front();
 			if (!sound._started) {
+				if (channel._resetDistance)
+					channel._distance = 0.0;
+
+				// Calculate an effective volume based on distance of source
 				_mixer->playStream(sound._waveFile->_soundType,
 					&sound._soundHandle, sound._waveFile->_stream,
-					-1, channel._volume, 0, DisposeAfterUse::NO);
+					-1, channel.getRawVolume(), 0, DisposeAfterUse::NO);
 				sound._started = true;
 			}
 		}
 	}
 }
 
+/*------------------------------------------------------------------------*/
+
+byte QMixer::ChannelEntry::getRawVolume() const {
+	// Emperically decided adjustment divisor for distances
+	const double ADJUSTMENT_FACTOR = 5.0;
+
+	double r = 1.0 + (_distance / ADJUSTMENT_FACTOR);
+	double percent = 1.0 / (r * r);
+
+	double newVolume = _volume * percent;
+	return (byte)newVolume;
+}
+
 } // End of namespace Titanic
diff --git a/engines/titanic/sound/qmixer.h b/engines/titanic/sound/qmixer.h
index 9a0ea85ede..b8c7f6dae2 100644
--- a/engines/titanic/sound/qmixer.h
+++ b/engines/titanic/sound/qmixer.h
@@ -197,9 +197,19 @@ class QMixer {
 		uint _volumeChangeEnd;
 		byte _volumeStart;
 		byte _volumeEnd;
+		// Distance of source
+		double _distance;
+		bool _resetDistance;
 
 		ChannelEntry() : _volume(0), _panRate(0), _volumeChangeStart(0),
-			_volumeChangeEnd(0), _volumeStart(0), _volumeEnd(0) {}
+			_volumeChangeEnd(0), _volumeStart(0), _volumeEnd(0),
+			_distance(0.0), _resetDistance(true) {}
+
+		/**
+		 * Calculates the raw volume level to pass to ScummVM playStream, taking
+		 * into the sound's volume level and distance from origin
+		 */
+		byte getRawVolume() const;
 	};
 private:
 	Audio::Mixer *_mixer;
@@ -290,7 +300,7 @@ public:
 	void qsWaveMixSetDistanceMapping(int iChannel, uint flags, const QMIX_DISTANCES &distances);
 
 	/**
-	 *
+	 * Sets the frequency/rate of sound playback
 	 */
 	void qsWaveMixSetFrequency(int iChannel, uint flags, uint frequency);