log vs exp question

[woodslanding]

I've been trying to create script that adds touch functionality to a fader. So if you touch it without dragging, it goes immediately to the position of the touch. Eventually, I'd like to have it move to the value at a specific rate, but that comes later.

It works fine so far, but then I realized that I needed my fader to be log taper. And I can't figure out what math to do on the mouse-position-based VAL (normalized to 0..1) to get log taper out.

VAL := log(VAL) gives negative numbers, and VAL := exp(VAL) gives numbers above 1. Neither is what I expected...

THANKS!
=e

edit: you can ignore the bit about negative and over-values--I was doing my range adjusting before the conversion. But I still don't know what usine's log taper is. Some research on audio taper makes it seem like this is not a universal standard... so I guess I need to know the math behind usine's implementation....

[woodslanding]

well, some more experimenting. I tried mouse * mouse, and that was better. mouse^4 seems about right. Guess that will do!

cheers,
-e

[woodslanding]

Here's the script, if it's useful to anybody....

Code: Select all

///////////////////////////////////////////////////////////
// TOUCH FADER
// eric moon 2024
// Wire this up to a fader to get a feature where you can touch the fader at a 
// spot, and it will go to that value.
// dragging works as usual.
// set logIN on, if your fader is set to logarithmic taper
// if your fader goes from 0 to 1, you shouldn't have to wire in min and max
// slop is how much mouse movement is needed to be considered 'dragging'
/////////////////////////////////////////////////////////////

// Globally enable/disable logging 
const DTAG = 'TextButton: ';
const DBUG_ON = TRUE;
procedure debug(s: string); begin if DBUG_ON then strace(DTAG + s); end;
procedure iDebug(s: string; num : integer); begin debug(s + '= ' + intToStr(num)); end;
procedure fDebug(s: string; num : single); begin debug(s + '= ' + floatToStr(num)); end;
// Always log, whether debug is on or not.
procedure Error(s: string); begin strace('ERROR-' + DTAG + s); end;
procedure fError(s: string; num : single); begin strace('ERROR-' + DTAG + s + '= ' + floatToStr(num)); end;
procedure iError(s: string; num : integer); begin strace('ERROR-' + DTAG + s + '= ' + intToStr(num)); end;

const LOG_TAPER = 1;
const LINEAR_TAPER = 0;

var mouseValIN, mouseDownIN, minIN, maxIN, slopIN, logIN, valueOUT: tParameter;

var gMouseVal: float;
var doneMousing, mouseDown: boolean;

// when we see the mouseDown, we note the mouseValue.  If it is the same (within slop) when the mouse is released
// just set the fader to that value

procedure init;
var i : integer;                   
begin                           
    SetModuleColor($804080+600000); 

    minIN := CreateParam('fader min', ptDatafield, pioInput); 
    minIN.DefaultValue(0);
    maxIN := CreateParam('fader max', ptDatafield, pioInput); 
    maxIN.DefaultValue(1); 

    logIN := CreateParam('log taper', ptSwitch, pioInput);
    
    mouseDownIN := CreateParam('mouse down', ptSwitch, pioInput);
    mouseValIN := CreateParam('mouse X', ptDatafield, pioInput);

    slopIN := CreateParam('slop in', ptDatafield, pioInput); 
    slopIN.DefaultValue(0.05);
    valueOUT := CreateParam('val to fader', ptDatafield, pioOutput);

    doneMousing := FALSE;

END;


//todo: could track mouse movement more continuously.
procedure mouse(down: boolean);
var current, travel, range, val: float;
begin
    if down then 
    begin
        mouseDown := TRUE;
        gMouseVal := mouseValIN.asFloat;   //store the mouse value
        fDebug('mouse val ',gMouseVal);
    end
    else
    begin
        mouseDown := FALSE;
        current := mouseValIN.asFloat;
        travel := abs(gMouseVal - current);        
        fDebug('travel ', travel);
        range := maxIN.asFloat - minIN.asFloat;
        //compute mouse movement 
        if travel < slopIN.asFloat then
        // set value of control
        begin       
            if logIN.asInteger = LOG_TAPER then current := current * current * current * current;
            val := minIn.asFloat + (current * range);            
            fDebug('val ', val);
            valueOUT.asFloat(val);
        end;
    end;
end;

procedure callback(n: integer);
begin
    if n = mouseDownIN then mouse(mouseDownIN.asInteger = 1);
end;

procedure processIdle();
begin
    if not mouseDown then 
    begin
        //doneMousing := FALSE;
        valueOUT.length(-1);
    end;
end;

[senso]

yes the power car replace the log/exp scale.