/**
* Abstract base class of interpolants over parametric samples.
*
* The parameter domain is one dimensional, typically the time or a path
* along a curve defined by the data.
*
* The sample values can have any dimensionality and derived classes may
* apply special interpretations to the data.
*
* This class provides the interval seek in a Template Method, deferring
* the actual interpolation to derived classes.
*
* Time complexity is O(1) for linear access crossing at most two points
* and O(log N) for random access, where N is the number of positions.
*
* References:
*
* http://www.oodesign.com/template-method-pattern.html
*
*/
class Interpolant {
constructor( parameterPositions, sampleValues, sampleSize, resultBuffer ) {
this.parameterPositions = parameterPositions;
this._cachedIndex = 0;
this.resultBuffer = resultBuffer !== undefined ?
resultBuffer : new sampleValues.constructor( sampleSize );
this.sampleValues = sampleValues;
this.valueSize = sampleSize;
this.settings = null;
this.DefaultSettings_ = {};
}
evaluate( t ) {
const pp = this.parameterPositions;
let i1 = this._cachedIndex,
t1 = pp[ i1 ],
t0 = pp[ i1 - 1 ];
validate_interval: {
seek: {
let right;
linear_scan: {
//- See http://jsperf.com/comparison-to-undefined/3
//- slower code:
//-
//- if ( t >= t1 || t1 === undefined ) {
forward_scan: if ( ! ( t < t1 ) ) {
for ( let giveUpAt = i1 + 2; ; ) {
if ( t1 === undefined ) {
if ( t < t0 ) break forward_scan;
// after end
i1 = pp.length;
this._cachedIndex = i1;
return this.copySampleValue_( i1 - 1 );
}
if ( i1 === giveUpAt ) break; // this loop
t0 = t1;
t1 = pp[ ++ i1 ];
if ( t < t1 ) {
// we have arrived at the sought interval
break seek;
}
}
// prepare binary search on the right side of the index
right = pp.length;
break linear_scan;
}
//- slower code:
//- if ( t < t0 || t0 === undefined ) {
if ( ! ( t >= t0 ) ) {
// looping?
const t1global = pp[ 1 ];
if ( t < t1global ) {
i1 = 2; // + 1, using the scan for the details
t0 = t1global;
}
// linear reverse scan
for ( let giveUpAt = i1 - 2; ; ) {
if ( t0 === undefined ) {
// before start
this._cachedIndex = 0;
return this.copySampleValue_( 0 );
}
if ( i1 === giveUpAt ) break; // this loop
t1 = t0;
t0 = pp[ -- i1 - 1 ];
if ( t >= t0 ) {
// we have arrived at the sought interval
break seek;
}
}
// prepare binary search on the left side of the index
right = i1;
i1 = 0;
break linear_scan;
}
// the interval is valid
break validate_interval;
} // linear scan
// binary search
while ( i1 < right ) {
const mid = ( i1 + right ) >>> 1;
if ( t < pp[ mid ] ) {
right = mid;
} else {
i1 = mid + 1;
}
}
t1 = pp[ i1 ];
t0 = pp[ i1 - 1 ];
// check boundary cases, again
if ( t0 === undefined ) {
this._cachedIndex = 0;
return this.copySampleValue_( 0 );
}
if ( t1 === undefined ) {
i1 = pp.length;
this._cachedIndex = i1;
return this.copySampleValue_( i1 - 1 );
}
} // seek
this._cachedIndex = i1;
this.intervalChanged_( i1, t0, t1 );
} // validate_interval
return this.interpolate_( i1, t0, t, t1 );
}
getSettings_() {
return this.settings || this.DefaultSettings_;
}
copySampleValue_( index ) {
// copies a sample value to the result buffer
const result = this.resultBuffer,
values = this.sampleValues,
stride = this.valueSize,
offset = index * stride;
for ( let i = 0; i !== stride; ++ i ) {
result[ i ] = values[ offset + i ];
}
return result;
}
// Template methods for derived classes:
interpolate_( /* i1, t0, t, t1 */ ) {
throw new Error( 'call to abstract method' );
// implementations shall return this.resultBuffer
}
intervalChanged_( /* i1, t0, t1 */ ) {
// empty
}
}
export { Interpolant };
