# Inverted parabolic envelope¶

• Author or source: James McCartney
• Type: envellope generation
• Created: 2002-01-17 00:57:43
code
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19``` ```dur = duration in samples midlevel = amplitude at midpoint beglevel = beginning and ending level (typically zero) amp = midlevel - beglevel; rdur = 1.0 / dur; rdur2 = rdur * rdur; level = beglevel; slope = 4.0 * amp * (rdur - rdur2); curve = -8.0 * amp * rdur2; ... for (i=0; i

```This parabola approximation seems more like a linear than a parab/expo envelope... or i'm mistaking something but i tryed everything and is only linear.
```
```slope is linear, but 'slope' is a function of 'curve'. If you imagine you threw a ball upwards, think of 'curve' as the gravity, 'slope' as the vertical velocity, and 'level' as the vertical displacement.
```
• Date: 2005-01-17 07:39:28
• By: asynth(at)io(dot)com
```This is not an approximation of a parabola, it IS a parabola.
This entry has become corrupted since it was first posted. Should be:

for (i=0; i<dur; ++i) {
out = level;
level += slope;
slope += curve;
}
```