private TabletopParams CreateFeatureParamsForSection(int section)
{
int numSections = sectionsProvider.NumSections();
double sectionLengthSeconds = sectionModel.TotalLength.TotalSeconds;
//first decide if it has a tabletop at all.
//the chance of it being something at all rises from 0% to 100%.
double progression = ((float)section + 1) / numSections; // <= 1
//if it's a tabletop:
double topLength =
randomizer.ProportionAlong(sectionModel.FeatureLengthVariation, progression,
sectionModel.MinFeatureLength.TotalSeconds,
sectionModel.MaxFeatureLength.TotalSeconds);
double maxRampLength = Math.Min(sectionModel.MaxRampLength.TotalSeconds, (sectionLengthSeconds - topLength) / 2);
if (sectionModel.MinRampLength.TotalSeconds > maxRampLength)
{
throw new InvalidOperationException($"MinRampLength must be <= maxRampLength. MinTabletopLength could be too high.");
}
// could feasibly be MinRampLength at the start of the track. Desirable? Yes, because other parameters constrain the dramaticness at the start.
double rampLength =
randomizer.ProportionAlong(sectionModel.RampLengthVariation, progression,
maxRampLength,
sectionModel.MinRampLength.TotalSeconds); // Max is first as shorter ramps are more dramatic (nearer the end of the track)
var result = new TabletopParams
{
RampLength = rampLength,
TopLength = topLength,
RampsUseSin2 = true
};
return(result);
}
private void ValidateParams(TabletopParams p)
{
double sectionLengthSeconds = sectionModel.TotalLength.TotalSeconds;
if (p.TopLength < 0)
{
throw new InvalidOperationException("TopLength must be >= 0");
}
if (p.RampLength < 0)
{
throw new InvalidOperationException("RampLength must be >= 0");
}
if (p.TopLength + 2 * p.RampLength > sectionLengthSeconds)
{
throw new InvalidOperationException("TopLength + 2*RampLength must be <= sectionLengthSeconds");
}
}
/* TopLength RampLength
* <--------------><->
* y| ________________
* | /ymax \ prefixLength (same both sides)
* | / \ <-->
* |____/ \____
* |ymin
* ________________________________x
* <-----------xmax-------------->
* the TopFrequency doesn't necessarily have to be greater than baseFrequency - but it must be >0.
*/
public static double GetY(double x, double xmax, double ymin, double ymax, TabletopParams p)
{
double prefixLength =
(xmax - p.TopLength - 2 * p.RampLength) / 2; //length of the bit at base frequency before the first ramp
double dy = ymax - ymin;
if (x < prefixLength)
{
//before the first ramp
return(ymin);
}
else if (x < prefixLength + p.RampLength)
{
// on the first ('up') ramp
double timeAlongRamp = x - prefixLength;
double proportionAlongRamp = timeAlongRamp / p.RampLength;
double proportionUpRamp = p.RampsUseSin2
? Math.Pow(Math.Sin(proportionAlongRamp * Math.PI / 2), 2)
: proportionAlongRamp;
return(ymin + proportionUpRamp * dy);
}
else if (x <= prefixLength + p.RampLength + p.TopLength)
{
// on the tabletop
return(ymax);
}
else if (x <= prefixLength + 2 * p.RampLength + p.TopLength)
{
//on the second ('down') ramp
double timeAlongRamp = x - prefixLength - p.RampLength - p.TopLength;
double proportionAlongRamp = timeAlongRamp / p.RampLength;
double proportionUpRamp = p.RampsUseSin2
? Math.Pow(Math.Sin(proportionAlongRamp * Math.PI / 2), 2)
: proportionAlongRamp;
return(ymin + (1 - proportionUpRamp) * dy);
}
else
{
//after the second ramp
return(ymin);
}
}
