[PD] Free rotation in GEM

Thu Jul 17 16:50:17 CEST 2008

This is rotating about local axes within the pot, which move when the pot
moves, creating the strange response.  The response should be based on a
global set of axes, which will remain constant and provide the response you
want.

On 7/17/08, PSPunch <shima at pspunch.com> wrote:
>
>
> Cyrille,
>
>
> With your advise, I think I've successfully implemented the algorithm I had
> in mind.
>
> The sad thing is, the algorithm I imagined did not exactly function in the
> way I wanted.
>
> i.e. 1,
> during one "drag session", when rotating the Y axis (dragging right or
> left) 180 degrees and then the x axis (up or down), it rotates as expected.
> However, when moving the axis in reverse order (making the teapot upside
> down, and then rotate) it does not rotate in the expected direction.
>
> i.e. 2,
> Behavior when dragging from one corner diagonally across the screen is not
> as expected.
>
> I've attached a sample patch.
>
>
> Probably the two problems are related. I need to look into this a bit
> more..
>
> --
> David Shimamoto
>
>
> ok.
>> i think i undersand.
>>
>> there is an other possibility based on the gemlist_info object that get
>> curent transformation matrix and convert it to rotation / translation ...
>>
>>
>> so, what i think is the most simple is :
>>    gemhead
>>    |
>>    rotateXYZ (for the drag rotation, should be (0 0 0) when you don't
>> drag)
>>    |
>>    rotateXYZ (for a feedback loop thanks to the rotation given by by the
>> last object on the chain)
>>    |
>>    object primitive
>>    |
>> gemlist         (the gemlist should be banged only at the end of the drag)
>> |
>> gemlist_info (get curent rotation at the end of the drag, and send it to
>> the 2nd rotate)
>>
>>
>> you can save few cpu using gemlist_matrix and GEMglMultMatrix.
>>
>> this is a bit like the algorythm you describ, execpt that everything is
>> computed on the GPU (it is more the Gem way to do).
>>
>> cyrille
>>
>> PSPunch a écrit :
>>
>>> Hi,
>>>
>>>
>>> My primary goal is to place an object you can rotate by dragging the
>>> mouse.
>>>
>>>
>>> Basically, whenever the mouse is clicked to start drag, I want to rotate
>>> the object on the X & Y axises. Up to this point is no problem, but I want
>>> the rotation to begin assuming the direction of the viewer being the bases
>>> of the axis.
>>>
>>> Using one [rotate] object, I can get the object to rotate in the behavior
>>> I expect only on the first drag.
>>>
>>> Ideally, each time the mouse button is released, the base (fundus?
>>> basal?) of the rotation vector should be updated... I think.
>>>
>>> By chaining [rotate] objects, I can use one to rotate the rotation axis
>>> and another to rotate the object from that point.
>>> However, I have not found a method of summing multiple drag actions.
>>>
>>>
>>> Although I may be wrong, I think what I need to do is,
>>>
>>>
>>> 1. Prepare two rotation axises
>>>    I. Angle of the axis
>>>    II.Angle of the current drag session
>>>
>>> 2. When the mouse button is clicked, rotate object to
>>>    angles I + II
>>>
>>> 3. When the mouse button is released, sum I + II and wait for
>>>    a new click.
>>>
>>>
>>> And again, although I may be wrong, my current understanding is that step
>>> 3 will require multiplying the X-Y-Z angles converted to quaternion, or some
>>> other method which will rotate the Z axis at some point by summing rotations
>>> based only on the X&Y axises.
>>>
>>>
>>> Using procedures completely different from the one mentioned abouve, I
>>> was able to achieve the expected behavior based on [accumrotate] but I found
>>> no simple way of managing the current angle.
>>>
>>> Unfortunately I have torn down the patch. If it would clarify anything, I
>>> will try to put together another one later today.
>>>
>>>
>>> Thanks for replies.
>>> --
>>> David Shimamoto
>>>
>>>
>>> Indeed,
>>>>
>>>> Seems to me all the matrix discussion does not get to the heart of the
>>>> question.
>>>>
>>>> So, Pspunch, what are you really trying to do?
>>>>
>>>> I agree with cyrille that It's very likely the normal rotation objects
>>>> will do what you want it to.
>>>>
>>>> If you are just wanting to rotate many times, using huge numbers then
>>>> tricks like: wrap 0 359 work well...
>>>>
>>>> ..b
>>>>
>>>> cyrille henry wrote:
>>>>
>>>>> hello
>>>>>
>>>>> sorry if i misunderstand.
>>>>> rotateXYZ will rotate in X direction, then in Y, finally in Z.
>>>>> if you wish to rotate in Z, then in X, you just need 2 rotate objects:
>>>>> the 1st for the rotation in Z, then an other for the rotation in X.
>>>>>
>>>>> anyway, there is no matrix manipulation that i was not able to do with
>>>>> rotate/rotateXYZ/translateXYZ/scaleXYZ/shearXY..
>>>>> so i'm quite sure you don't need anything else than this standard
>>>>> objects for simple matrix rotation.
>>>>>
>>>>> so i think you need 1 [rotate] to rotate the vector axis of the object,
>>>>> then a accumrotate.
>>>>> if i misunderstood, could you please describe your problem better.
>>>>>
>>>>> I think you can also use GEMgl objects to multiply the matrix with a
>>>>> custom one, but it's to much complex for what you need.
>>>>>
>>>>> cyrille
>>>>>
>>>>>
>>>>>
>>>>> PSPunch a écrit :
>>>>>
>>>>>> Hi Mathieu,
>>>>>>
>>>>>>
>>>>>> I have not looked into GridFlow much, but I had the impression that
>>>>>> its main concept was to add matrix manipulation features to Pd, all of its
>>>>>> visual capabilities being just one of the many results of data you can
>>>>>> manipulate with matrix. (or is the egg first?)
>>>>>>
>>>>>>
>>>>>> Anyway, understanding its marvelous potentials, I have lately been
>>>>>> stuck with Windows platforms. At least I got your point that utilizing
>>>>>> GridFlow only for crunching numbers may work but not so efficient.
>>>>>>
>>>>>>
>>>>>>
>>>>>> What I am trying to do is rotate the vector axis of the object before
>>>>>> applying [rotation]. This also calls for a method of summing the rotations
>>>>>> when applying multiple times (and my current understanding is that this can
>>>>>> only be done by multiplying the quaternion on each rotation)
>>>>>>
>>>>>> If there is no solution at the moment, perhaps Gem could use a few
>>>>>> extra objects to ease advanced rotations?
>>>>>>
>>>>>> I feel like I am complaining about lack of features without pointing
>>>>>> out what exactly is missing, when I should be blaming my lack of math
>>>>>> skills.
>>>>>>
>>>>>> hmmm..
>>>>>>
>>>>>> --
>>>>>> David Shimamoto
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, 16 Jul 2008, PSPunch wrote:
>>>>>>>
>>>>>>> Trying to achieve free rotation *without* using [accumrotate], I have
>>>>>>>> come across concepts such as multiplying matrixs and converting a
>>>>>>>> matrix
>>>>>>>> to "quarternion"
>>>>>>>> How do you implement precise control of rotation matrixs?
>>>>>>>> Is this exactly what people use GridFlow for?
>>>>>>>>
>>>>>>> If you tried GridFlow's bundled examples you'd see what I use
>>>>>>> GridFlow for. I suppose that I could add some other people's examples in the
>>>>>>> package, if they sent it to me for that purpose. There is already one patch
>>>>>>> by Roman Häfeli in GridFlow's examples though.
>>>>>>>
>>>>>>> GridFlow does not support quaternions. I bet it's possible to add
>>>>>>> support for it using abstractions, but it wouldn't be fast. But I'm willing
>>>>>>> to add it to the core... there's already a complex-number section in
>>>>>>> number.c, why not quaternion product? It would be called [# H.*] where H
>>>>>>> stands for Hamilton (in math the letter Q is already reserved for rationals,
>>>>>>> so I'd use H even though the concept of rational reasonably couldn't appear
>>>>>>> in that particular place).
>>>>>>>
>>>>>>>  _ _ __ ___ _____ ________ _____________ _____________________ ...
>>>>>>> | Mathieu Bouchard - tél:+1.514.383.3801, Montréal, Québec
>>>>>>>
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