[PD] Multiblob and matrices...

IOhannes m zmoelnig zmoelnig at iem.at
Sat Apr 4 15:14:37 CEST 2009

Simon Ball wrote:
> Hi List

it seems like i received this email multiple times...

> However, there are few areas I am still confused about. First of all, I am
> unsure of how to extract muliple co-ordinates from [pix_multiblob]. I
> understand that the data from multiblob is collated within a matrix. I am
> able to see this in the pd window when I print. However, I am unsure how to
> use a matrix. Is there a certain object that I should be sending to from
> [pix_multiblob]? And in turn, how would I convert the matrix into xy
> co-ordinates.

there is a separate library dedicated to the kind of matrices output by
[pix_multiblob]; it's called "iemmatrix".

however, you should have an understanding of matrices in order to use it.

matrices of this form are simple messages which you can treat like any
other message.
attached are two examples on how to extract the rows of a matrix (and
pix_multiblob will give you one row per blob; so this is interesting
data), one using iemmatrix ([pix_rows]) and one using zexy ([pix_rowz]).
it is left as an exercise for the user to make a pd-vanilla implementation.

just send the mtx-output of [pix_multiblob] to the object, and you will
get nice lists for each blob, starting with the index of the blob
(zero-based) and then comes the data.
use [route] to filter the relevant blobs and [unpack] to access the data.

> In the archives I found a response to similar a question saying there was a
> gem example with matrix and multiblob, but I can not seem to find it. Any
> idea what and where this is?

there's an abstraction called [pix_blobtracker] which uses
[pix_multiblob] and matrix operations to track blobs.

> Hope thats not too many questions. And is it easier for the list if I divide
> questions up (for archive purposes perhaps)?

personally i would prefer separate threads for separate questions for
starters. it always ends in confusion, but we could try to delay this...

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