I need discrete stopping points on a knob

1

ok so, I am trying to update my plugin with what my client wants. he wants discrete stopping points on a certain knob but i’ve been looking on the forums and i can’t find how to do it. can someone help me out here?

2

Using an AudioParameterInt or AudioParameterChoice instead of an AudioParamerFloat will automatically give you discrete stopping points.

3

but I need it at a specific incriment of 0.1 from a range of -100 db to +60, would it still do that or do i need to define it

4

that or you just fix the display to only show one number after the floating point separator :slight_smile:

5

ok i tried this and it just showed a ton of errors

6

ok i think i got it… I just needed to change a decimal point

7

The Slider uses the NormalisableRange of the parameter.
When you setup the NormalisableRange you can also supply a step range, as well with a lambda to create programmatic legal positions to snap to.

Screenshot 2024-01-17 at 11.29.02
Screenshot 2024-01-17 at 11.29.021127×488 64.6 KB

The signature of the remap function is:

std::function<ValueType(ValueType rangeStart, ValueType rangeEnd, ValueType valueToRemap)>

auto snapToValue = [](float start, float end, float value)
{
    // do your logic here and return the snapped value
};

Note the decimal point probably only works visually, so the user can still dial in values that don’t snap

8

gotcha, thanks so much for the help

9

ok so im still having errors pop up: here’s my code:
juce::AudioProcessorValueTreeState::ParameterLayout OnlyGainsAudioProcessor::createParameterLayout()
{
APVTS::ParameterLayout layout;

// Define snapToValue function before using it
std::function<float(float, float, float)> snapToValue = [](float start, float end, float value)
{
    // Snap to increments of 0.1
    return std::round(value / 0.1f) * 0.1f;
};

using namespace juce;

layout.add(std::make_unique<AudioParameterFloat>(juce::ParameterID{ "Gain", 1 }, "Gain", NormalisableRange<float>(-100.0f, 60.0f, snapToValue), 0));

auto strFromValDb = [](float val, int)
{
    return juce::String(val, 2) + "Gain";
};

return layout;

}
and heres the errors:

image
image870×69 3.89 KB

10

The compiler tells you that it cannot find a constructor that matches the arguments you give to NormalisableRange. Indeed you only pass 3 arguments (float, float, ValueRemapFunction) and there’s no such constructor like this mentioned in the documentation…

What you want to use is this one as Daniel pointed out: JUCE: NormalisableRange< ValueType > Class Template Reference

I suppose you want to pass your snapToValue lambda as the 5th argument. The 3rd argument is also a lambda to describe how you convert from [0,1] (i.e. normalised values) to your expanded range (i.e. your -100dB to 60dB in your case). The 4th is the other way around (from [-100, 60] to [0,1]).

11

If you only need to set the slider/parameter’s sensitivity to 0.1 it is as easy as:

layout.add(std::make_unique<AudioParameterFloat>(juce::ParameterID{ "Gain", 1 }, "Gain", 
    NormalisableRange<float>(-100.0f, 60.0f, 0.1f), 0.0f));

I had a usecase in mind, where the interval changes, e.g. I used in an equalizer in 1 Hz up to 1kHz, then I switched to the interval of 0.01 kHz and so on…
But in that case you have to supply ALL mapping functions to satisfy the constructor:

juce::NormalisableRange<float> range(-100.0f, 60.0f,
    [](float start, float end, float value) { return juce::jmap (value, start, end); },
    [](float start, float end, float value) { return juce::jmap (value, start, end, 0.0f, 1.0f); },
    [](float start, float end, float value) { return juce::roundToInt (value * 10.0f) * 0.1f; });
layout.add(std::make_unique<AudioParameterFloat>(juce::ParameterID{ "Gain", 1 }, "Gain", range, 0.0f));

With the later approach you have tons of options

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