[PD] Creating a line in Gem

Antoine Villeret antoine.villeret at gmail.com
Tue Dec 18 17:10:14 CET 2012


just to notice, I used to use [GEMglBegin] -> [GEMglVertex2d] ->
[GEMglVertex2d] -> [GEMglEnd] structure to draw line directly on
the first GEMglVertex2d is the starting point, the second the end point
in conjunction with [gemlist] you can draw line with an arbitrary
number of segments which is -- but it's only my point of view -- more
convinient than using multiple rectangles (and it's also more
efficient because there is no extra point)
the line width is set with the [GEMglLineWidth] object...
a good example for that is the pix_opencv_countours-help.pd patch
which is in pix_opencv (but i know it's not really easy to find it nor
to build it but we are currently working to improve that)


do it yourself
Google lit ce mail...
si vous refusez cela, utilisez l'adresse antoine.villeret [at] free.fr
pour me contacter

2012/12/18 Alexandros Drymonitis <adrcki at gmail.com>:
> Thanks Cyrille, this is what I wanted.
> On Tue, Dec 18, 2012 at 2:25 PM, Cyrille Henry <ch at chnry.net> wrote:
>> hello,
>> ok, i can see why it's complicated to use rectangle in this situation.
>> But i did not see the problem of the curve object.
>> in order to "give this line an angle", i think it's best to use the rotate
>> object than the shear.
>> computation are not that hard with rectangle if you do it right :
>> gemhead
>> translateXYZ <- give random position
>> rotateXYZ  <- give Z rotation
>> scaleXYZ 0 1 1 <- change X scale to grow
>> translate 0.5 0 0 <- to move the primitive so that it's not center
>> rectangle 0.5 0.1 <- 0.1 is line width
>> starting point is given by the initial translate.
>> ending point is just : starting point + cos(angle)*line length for X
>> coordinate,
>> replace cos with sin for Y position (be aware that Gem is in deg, while pd
>> is in rad)
>> but if you prefer having random initial position and random final
>> position, then a [curve 2] object can be more helpful.
>> see both solution in attachment.
>> cheers
>> Cyrille
>> Le 18/12/2012 12:46, Alexandros Drymonitis a écrit :
>>> Hi all,
>>> I've been trying to render a line in Gem, so I'm wondering if it's best
>>> to use [curve] (which is actually a curve as it indicates), or [rectangle]
>>> with a very small x value, so that it looks like a line.
>>> My problem is that I want to give this line an angle, so I've been using
>>> [shearXY] for now. I also want to make the line grow from nothing to the
>>> full desired length, but with [rectangle] it will grow from the middle, so
>>> in order to make it grow from the starting point to the ending point, you
>>> have to give [rectangle] a continuous x,y offset.
>>> This way it's really hard to determine the starting and ending point of
>>> the line. So, If for example the x,y coordinates of the starting and ending
>>> point are random, then the angle and length will also be random and you'll
>>> have to manipulate three different objects simultaneously ([rectangle],
>>> [translate] and [shearXY]), and I'm not sure if I can find the formula for
>>> all these calculations.
>>> Is there an easier technique for this?
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