float lwEvalEnvelope( lwEnvelope *env, float time )
{
lwKey *key0, *key1, *skey, *ekey;
float t, h1, h2, h3, h4, in, out, offset = 0.0f;
int noff;
/* if there's no key, the value is 0 */
if ( env->nkeys == 0 ) return 0.0f;
/* if there's only one key, the value is constant */
if ( env->nkeys == 1 )
return env->key->value;
/* find the first and last keys */
skey = ekey = env->key;
while ( ekey->next ) ekey = ekey->next;
/* use pre-behavior if time is before first key time */
if ( time < skey->time ) {
switch ( env->behavior[ 0 ] )
{
case BEH_RESET:
return 0.0f;
case BEH_CONSTANT:
return skey->value;
case BEH_REPEAT:
time = range( time, skey->time, ekey->time, NULL );
break;
case BEH_OSCILLATE:
time = range( time, skey->time, ekey->time, &noff );
if ( noff % 2 )
time = ekey->time - skey->time - time;
break;
case BEH_OFFSET:
time = range( time, skey->time, ekey->time, &noff );
offset = noff * ( ekey->value - skey->value );
break;
case BEH_LINEAR:
switch ( skey->shape ) {
case SHAPE_STEP:
return skey->value;
case SHAPE_LINE:
return ( skey->value - skey->next->value )
/ ( skey->time - skey->next->time )
* ( time - skey->next->time )
+ skey->next->value;
case SHAPE_TCB:
case SHAPE_HERM:
case SHAPE_BEZI:
out = outgoing( skey, (Key*)(skey->next) )
/ ( skey->next->time - skey->time );
return out * ( time - skey->time ) + skey->value;
case SHAPE_BEZ2:
return ( skey->param[ 1 ] - skey->param[ 3 ] )
/ ( skey->param[ 0 ] - skey->param[ 2 ] )
* ( time - skey->time )
+ skey->value;
}
}
}
/* use post-behavior if time is after last key time */
else if ( time > ekey->time ) {
switch ( env->behavior[ 1 ] )
{
case BEH_RESET:
return 0.0f;
case BEH_CONSTANT:
return ekey->value;
case BEH_REPEAT:
time = range( time, skey->time, ekey->time, NULL );
break;
case BEH_OSCILLATE:
time = range( time, skey->time, ekey->time, &noff );
if ( noff % 2 )
time = ekey->time - skey->time - time;
break;
case BEH_OFFSET:
time = range( time, skey->time, ekey->time, &noff );
offset = noff * ( ekey->value - skey->value );
break;
case BEH_LINEAR:
switch ( ekey->shape ) {
case SHAPE_STEP:
return ekey->value;
case SHAPE_LINE:
return ( ekey->value - ekey->prev->value )
/ ( ekey->time - ekey->prev->time )
* ( time - ekey->prev->time )
+ ekey->prev->value;
case SHAPE_TCB:
case SHAPE_HERM:
case SHAPE_BEZI:
in = incoming( (Key*)(ekey->prev), (Key*)ekey )
/ ( ekey->time - ekey->prev->time );
return in * ( time - ekey->time ) + ekey->value;
case SHAPE_BEZ2:
return ( ekey->param[ 3 ] - ekey->param[ 1 ] )
/ ( ekey->param[ 2 ] - ekey->param[ 0 ] )
* ( time - ekey->time )
+ ekey->value;
}
}
}
/* get the endpoints of the interval being evaluated */
key0 = env->key;
while ( time > key0->next->time )
key0 = key0->next;
key1 = key0->next;
/* check for singularities first */
if ( time == key0->time )
return key0->value + offset;
else if ( time == key1->time )
return key1->value + offset;
/* get interval length, time in [0, 1] */
t = ( time - key0->time ) / ( key1->time - key0->time );
/* interpolate */
switch ( key1->shape )
{
case SHAPE_TCB:
case SHAPE_BEZI:
case SHAPE_HERM:
out = outgoing( key0, (Key*)key1 );
in = incoming( (Key*)key0, (Key*)key1 );
hermite( t, &h1, &h2, &h3, &h4 );
return h1 * key0->value + h2 * key1->value + h3 * out + h4 * in + offset;
case SHAPE_BEZ2:
return bez2( (Key*)key0, (Key*)key1, time ) + offset;
case SHAPE_LINE:
return key0->value + t * ( key1->value - key0->value ) + offset;
case SHAPE_STEP:
return key0->value + offset;
default:
return offset;
}
}
float bez3(float p0, float p1, float p2, float p3, float out){
return bez2(lerp(p0, p1, out), lerp(p1, p2, out), lerp(p2, p3, out), out);
}