# Re: What to do wanting a 4th order Bézier?

```On 21.09.2016 19:22, Urs Liska wrote:
```
```Am 21.09.2016 um 19:18 schrieb Carl Sorensen:
```
```On 9/21/16 10:22 AM, "Urs Liska"<u...@openlilylib.org>  wrote:
```
```         The other thing I came across is the specification of the
inflection*point*. Basically the idea of specifying independent
X and Y ratios between the slur's endpoints seems practical, as
it is pretty predictable. But I realized that this only works
well when the endpoints are sufficiently different on the
Y-scale. If the slur is horizontal then*any*  inflection will
necessarily be on that same horizontal line! So I need a
suggestion what could be a suitable, predictable*and*
un-limited approach to specifying this.
```
```I think that you could use the X fraction as the X coordinate of the
inflection point.  And you could use a Y offset (in staff spaces from the
starting point) as the Y coordinate of the inflection point.  It seems
that should be relatively easy to implement.
```
```Implementing that is easy, of course. What I'm thinking about mostly is
the predictability of the results when anything changes, for example the
Y coordinate of either point.```
```
What would you think of using a staff-space offset for Y (as per your
suggestion) but apply it to the vertical center between the two
endpoints? That way the whole slur should somewhat shift together with
changed Y of an end point.

Would it be acceptable to have a pair? as an argument when the two
elements*do*  refer to X and Y but with completely different behaviour?
Or should that then be separated to two individual properties?
```
```
```
That sounds like way over the top. The user interface should be reasonably easy to understand, so I’d prefer a simple staff-space offset for Y. It seems like a good idea to do it relative to the vertical center between the two endpoints, then 0 as a default is sensible.
```
Best, Simon

_______________________________________________
lilypond-user mailing list
lilypond-user@gnu.org
https://lists.gnu.org/mailman/listinfo/lilypond-user
```