[Interest] sin wave with QPainterPath between two points

Patrick Stinson patrickkidd at gmail.com
Thu Jul 20 10:30:41 CEST 2017


Also it should be between two arbitrary points, so the sine wave may go from top-right to bottom left, for example.

> On Jul 20, 2017, at 1:28 AM, Elvis Stansvik <elvstone at gmail.com> wrote:
> 
> 2017-07-20 10:23 GMT+02:00 Jean-Michaël Celerier
> <jeanmichael.celerier at gmail.com <mailto:jeanmichael.celerier at gmail.com>>:
>> You can just compute the sine directly :
>> 
>>   for(int i = 0; i < width; i++)
>>   {
>>     int x = i;
>>     int y = height / 2 + amplitude * std::sin(2 * M_PI * freq * i / width +
>> phase);
>>     path.lineTo(x, y);
>>   }
> 
> I think he wanted to avoid an approximation with straight lines and
> use cubic beziers.
> 
> Jean-Michaël: There seems to be many pages explaining the theory
> behind sine approximation using Beziers if you Google.
> 
> Elvis
> 
>> 
>> 
>> 
>> 
>> 
>> -------
>> Jean-Michaël Celerier
>> http://www.jcelerier.name
>> 
>> On Thu, Jul 20, 2017 at 9:47 AM, Patrick Stinson <patrickkidd at gmail.com>
>> wrote:
>>> 
>>> Hello! I want to figure out how to draw a sin wave between two QPointF’s
>>> using QPainterPath. Calculating the cubic control points seems like the best
>>> way, but I am far from mastering that theory.
>>> 
>>> This is a diagramming app and the goal is to get a squiggly line between
>>> two objects.
>>> 
>>> Thanks!
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>>> Interest at qt-project.org
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>>> 
>> 
>> 
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