[PD] Free rotation in GEM

PSPunch shima at pspunch.com
Wed Jul 16 04:09:26 CEST 2008

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.


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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