[PD] Creating a line in Gem

[Antoine Villeret]

hi,

just to notice, I used to use [GEMglBegin] -> [GEMglVertex2d] ->
[GEMglVertex2d] -> [GEMglEnd] structure to draw line directly on
screen
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)

best

a
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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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>
>
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