You're using the [scale] formula from @classic_mode in Max7, which
exists for compatibility with IRCAM, but it's clearly wrong. (There's no
way mapping 13.3 from 0-127 to -1 to 1 should result in something so
close to -1. Just try a few different exponents and you'll see that
there's a bug in the Max code. And there are lots of bug reports out
there about it.)
That's why they introduced an alternate mode for [scale] in Max, which
can be switch in the Inspector.
For non-classic (modern) mode, the documentation gives you this equation:
((x-in_low)/(in_high-in_low) == 0) ? out_low :
(((x-in_low)/(in_high-in_low)) > 0) ? (out_low + (out_high-out_low) *
((x-in_low)/(in_high-in_low))^exp) : ( out_low + (out_high-out_low) *
-((((-x+in_low)/(in_high-in_low)))^(exp)))
Translated to expr as:
[expr if ((($f1-in_low)/(in_high-in_low)==0), out_low, if
((($f1-in_low)/(in_high-in_low)>0),
out_low+(out_high-out_low)*pow(($f1-in_low)/(in_high-in_low), power),
out_low+(out_high-out_low)*-1*pow((-1*$f1+in_low)/(in_high-in_low),
power)))]
Switch off classic mode in the inspector in Max7, and you get the same
result as expr above, the very sensible -0.817072.
Joel
On 06/19/2015 05:39 PM, Alexandre Torres Porres wrote:
Howdy, so I'm cloning the scale object from Max, to make an object and
include in the cyclone library. It converts range input (low_in /
high_in) to a range output (low_out / high_out). It has a logarithmic
curve for rescaling according to a fifth argument/inlet. I did copy
into expr the formula described in the reference of Max6/7 (max's 5
was just wrong, copied from [linedrive]) - well, it didn't work! Would
anyone know if I'm doing something wrong or if the reference is not
telling the truth?
The formula, as described in the reference is: (out_low +
(out_high-out_low) * ( (out_high - out_low) * exp(-1 *
(in_high-in_low) * log(power)) * exp(x * log(power)) ))
Here's my patch with that formula into expr. The output with the
parameters I have should be -0.997347 - as that's the output I get in
Max. But instead, it's giving -0.994694...
thanks
=================
#N canvas 24 23 488 340 10;
#X obj 215 154 v out_low;
#X obj 233 132 v out_high;
#X obj 288 110 v power;
#X obj 152 130 v in_high;
#X obj 115 153 v in_low;
#X floatatom 58 248 0 0 0 0 - - -;
#X obj 58 197 expr (out_low + (out_high-out_low) * ( (out_high - out_low)
* exp(-1*(in_high-in_low)*log(power)) * exp($f1*log(power)) ));
#X msg 115 102 0;
#X msg 152 102 127;
#X msg 215 99 -1;
#X msg 249 97 1;
#X msg 288 86 1.06;
#X obj 90 31 loadbang;
#X obj 90 60 t b b;
#X msg 58 107 13.3;
#X connect 6 0 5 0;
#X connect 7 0 4 0;
#X connect 8 0 3 0;
#X connect 9 0 0 0;
#X connect 10 0 1 0;
#X connect 11 0 2 0;
#X connect 12 0 13 0;
#X connect 13 0 14 0;
#X connect 13 1 11 0;
#X connect 13 1 10 0;
#X connect 13 1 9 0;
#X connect 13 1 8 0;
#X connect 13 1 7 0;
#X connect 14 0 6 0;
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