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Update the multi-zone reverb example for clarity

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This commit is contained in:
Chris Robinson
2018-02-19 21:46:08 -08:00
parent 51c6d13c0f
commit 9fc2dbe063
1 changed files with 52 additions and 47 deletions
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examples/almultireverb.c
+52 -47
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@@ -25,7 +25,7 @@
/* This file contains an example for controlling multiple reverb zones to
* smoothly transition between reverb environments. The general concept is to
* extend single-reverb by also tracking the closest adjacent environment, and
* utilizing EAX Reverb's panning vectors to position them relative to the
* utilize EAX Reverb's panning vectors to position them relative to the
* listener.
*/
@@ -42,6 +42,11 @@
#include "common/alhelpers.h"
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
/* Filter object functions */
static LPALGENFILTERS alGenFilters;
static LPALDELETEFILTERS alDeleteFilters;
@@ -91,7 +96,7 @@ static int LoadEffect(ALuint effect, const EFXEAXREVERBPROPERTIES *reverb)
alGetError();
/* Prepate the effect for EAX Reverb (standard reverb doesn't contain
/* Prepare the effect for EAX Reverb (standard reverb doesn't contain
* the needed panning vectors).
*/
alEffecti(effect, AL_EFFECT_TYPE, AL_EFFECT_EAXREVERB);
@@ -228,7 +233,7 @@ static ALfloat dot_product(const ALfloat vec0[3], const ALfloat vec1[3])
int main(int argc, char **argv)
{
const int MaxTransitions = 8;
static const int MaxTransitions = 8;
EFXEAXREVERBPROPERTIES reverb0 = EFX_REVERB_PRESET_CASTLE_LARGEROOM;
EFXEAXREVERBPROPERTIES reverb1 = EFX_REVERB_PRESET_CASTLE_LONGPASSAGE;
struct timespec basetime;
@@ -356,7 +361,8 @@ int main(int argc, char **argv)
* Note that unlike single-zone reverb, where you can store one effect per
* preset, for multi-zone reverb you should have one effect per environment
* instance, or one per audible zone. This is because we'll be changing the
* effects' properties in real-time based on the environment instance.
* effects' properties in real-time based on the environment instance
* relative to the listener.
*/
alGenEffects(2, effects);
if(!LoadEffect(effects[0], &reverb0) || !LoadEffect(effects[1], &reverb1))
@@ -381,7 +387,7 @@ int main(int argc, char **argv)
assert(alGetError()==AL_NO_ERROR && "Failed to set effect slot");
/* For the purposes of this example, prepare a filter that optionally
* silences the direct path. This allows us to hear just the reverberation.
* silences the direct path which allows us to hear just the reverberation.
* A filter like this is normally used for obstruction, where the path
* directly between the listener and source is blocked (the exact
* properties depending on the type and thickness of the obstructing
@@ -409,12 +415,10 @@ int main(int argc, char **argv)
alSource3i(source, AL_AUXILIARY_SEND_FILTER, slots[1], 1, AL_FILTER_NULL);
assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source");
/* Get the base time, and set the example to stop after a number of
* transitions.
*/
/* Get the current time as the base for timing in the main loop. */
altimespec_get(&basetime, AL_TIME_UTC);
loops = MaxTransitions;
printf("Transition %d of %d...\n", (MaxTransitions-loops+1), MaxTransitions);
loops = 0;
printf("Transition %d of %d...\n", loops+1, MaxTransitions);
/* Play the sound for a while. */
alSourcePlay(source);
@@ -432,6 +436,8 @@ int main(int argc, char **argv)
const ALfloat portal_radius = 2.5f;
ALfloat other_dir[3], this_dir[3];
ALfloat local_norm[3];
ALfloat local_dir[3];
ALfloat local_radius;
ALfloat dist, timediff;
struct timespec curtime;
@@ -456,34 +462,30 @@ int main(int argc, char **argv)
*/
timediff -= 4.0f;
basetime.tv_sec += 4;
if(--loops > 0)
printf("Transition %d of %d...\n", (MaxTransitions-loops+1), MaxTransitions);
if(++loops < MaxTransitions)
printf("Transition %d of %d...\n", loops+1, MaxTransitions);
}
/* Move the portal according to the amount of time passed. other_dir
* represents the listener-relative point from the current zone to the
* other adjacent zone.
/* Move the portal according to the amount of time passed. local_dir
* represents the listener-relative point to the adjacent zone.
*/
other_dir[0] = portal_pos[0] + portal_vel[0]*timediff;
other_dir[1] = portal_pos[1] + portal_vel[1]*timediff;
other_dir[2] = portal_pos[2] + portal_vel[2]*timediff;
/* In a normal application you may also want to scale down the portal's
* apparent radius depending on its local angle, since less of the
* adjacent zone would be in view of the listener. You would also want
* to rotate the portal's normal according to the listener orientation.
local_dir[0] = portal_pos[0] + portal_vel[0]*timediff;
local_dir[1] = portal_pos[1] + portal_vel[1]*timediff;
local_dir[2] = portal_pos[2] + portal_vel[2]*timediff;
/* A normal application would also rotate the portal's normal given the
* listener orientation, to get the listener-relative normal.
*
* For this example, the portal is always head-on so there's no need to
* adjust the radius. But every other transition iteration inverts the
* normal, which essentially simulates a different portal moving in
* closer than the last one, switching the old adjacent zone to a new
* one.
* For this example, the portal is always head-on but every other
* transition negates the normal. This effectively simulates a
* different portal moving in closer than the last one that faces the
* other way, switching the old adjacent zone to a new one.
*/
local_norm[0] = portal_norm[0] * ((loops&1) ? -1.0f : 1.0f);
local_norm[1] = portal_norm[1] * ((loops&1) ? -1.0f : 1.0f);
local_norm[2] = portal_norm[2] * ((loops&1) ? -1.0f : 1.0f);
/* Calculate the distance from the listener to the portal. */
dist = sqrtf(dot_product(other_dir, other_dir));
dist = sqrtf(dot_product(local_dir, local_dir));
if(!(dist > 0.00001f))
{
/* We're practically in the center of the portal. Give the panning
@@ -510,19 +512,24 @@ int main(int argc, char **argv)
ALfloat spread;
/* Normalize the direction to the portal. */
other_dir[0] /= dist;
other_dir[1] /= dist;
other_dir[2] /= dist;
local_dir[0] /= dist;
local_dir[1] /= dist;
local_dir[2] /= dist;
/* Scale the radius according to its local angle. The visibility to
* the other zone reduces as the portal becomes perpendicular.
*/
local_radius = portal_radius * fabsf(dot_product(local_dir, local_norm));
/* Calculate the 'spread' of the portal, which is the amount of
* coverage the other zone has.
* coverage the other zone has around the listener.
*/
spread = atan2f(portal_radius, dist) / ((ALfloat)M_PI);
spread = atan2f(local_radius, dist) / (ALfloat)M_PI;
/* Figure out which zone we're in, given the direction to the
* portal and its normal.
*/
if(dot_product(other_dir, local_norm) <= 0.0f)
if(dot_product(local_dir, local_norm) <= 0.0f)
{
/* We're in front of the portal, so we're in Zone 0. */
this_effect = effects[0];
@@ -535,20 +542,18 @@ int main(int argc, char **argv)
other_effect = effects[0];
}
/* Pan the current zone to the opposite direction of the portal,
* and take the remaining percentage of the portal's spread. As the
* portal's spread increases, this zone's spread decreases, which
* is indicated by a larger panning vector.
*/
this_dir[0] = other_dir[0] * -spread;
this_dir[1] = other_dir[1] * -spread;
this_dir[2] = other_dir[2] * -spread;
/* Scale the other zone's panning vector down as the portal's
* spread increases, so that it covers more.
* spread increases, so that it envelops the listener more.
*/
other_dir[0] *= 1.0f-spread;
other_dir[1] *= 1.0f-spread;
other_dir[2] *= 1.0f-spread;
other_dir[0] = local_dir[0] * (1.0f-spread);
other_dir[1] = local_dir[1] * (1.0f-spread);
other_dir[2] = local_dir[2] * (1.0f-spread);
/* Pan the current zone to the opposite direction of the portal,
* and take the remaining percentage of the portal's spread.
*/
this_dir[0] = local_dir[0] * -spread;
this_dir[1] = local_dir[1] * -spread;
this_dir[2] = local_dir[2] * -spread;
/* Now set the effects' panning vectors. */
alEffectfv(this_effect, AL_EAXREVERB_REFLECTIONS_PAN, this_dir);
@@ -568,7 +573,7 @@ int main(int argc, char **argv)
al_nssleep(10000000);
alGetSourcei(source, AL_SOURCE_STATE, &state);
} while(alGetError() == AL_NO_ERROR && state == AL_PLAYING && loops > 0);
} while(alGetError() == AL_NO_ERROR && state == AL_PLAYING && loops < MaxTransitions);
/* All done. Delete resources, and close down SDL_sound and OpenAL. */
alDeleteSources(1, &source);