Hi Ivan!
I'm sorry for the late response.
El martes, 26 de noviembre de 2013, Ivan Mahonin escribió:
> Hi, Carlos!
>
> Actual transformation splitted by two parts 'transformation' and
> 'origin_transformation'.
> 'origin_transformation' determines rotation center and angles of apllying
> X and Y scaling. Also it determines visual representation of
> transformation handles in workarea.
>
> Main condition of such splitting is - 'origin_transformation' should have
> no effect when 'transformation' is identity. 'origin_transformation' only
> determines how 'transformation' will applied.
I have no doubts about the need of an origin of the transformation
>
> So transformation matrix can be calculated only for both parameters
> 'origin_transformation' and 'transformation' (not for each one).
>
> Anyway I'll think about generic solution how to split matrix to origin and
> transformation parts.
You can apply the inverse of the matrix of the origin transformation,
then the transformation matrix itself, and the restore the origin
transformation again by applying the origin transformation matrix once more
time. Notice that you have to push matrixes in reverse order before they
are multiplied to the vector to transform.
What I wanted to ask is that you can do internally the calculations as
matrixes, so inverse are quite easy to calculate just transposing the
matrix due to their orthogonal property.
Cheers
>
> Ivan
>
> > Hi!
> > I'm following the changes being made in the bones branch by Ivan.
> >
> > The Transformation class (as a new type) is a great idea and its
> > representation as composite of rotation, translation and both scales is
> > great. From the point of view of the user it is good, because user can
> > fine
> > tune the values editing them manually.
> >
> > But I wonder why internally it is not represented as a matrix. With a
> > 3x3 matrix (augmented 2x2 matrix [1]) it is possible to produce not only
> > rotation translation and scale but also shear mapping perspective
> > projection or homothety due to the properties of the affine
> > transformations
> > [2]. Then we could use that matrix in other kind of effects without need
> > to
> > rewrite more code since the matrix algebra is exactly the same.
> >
> > Cheers, Carlos
> >
> > [1] http://en.wikipedia.org/wiki/Augmented_matrix
> > [2] http://en.wikipedia.org/wiki/Affine_transformation
> >
> >
> > --
> > Carlos
> > http://synfig.org
> >
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>
>
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--
Carlos
http://synfig.org
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