Re: [filter-effects] Animation between filter functions

Dirk Schulze wrote:
> 1) One of the filter function lists consist of at least one SVG
> filter reference (URL or<child>  selector)

Are there other properties that take lists of values that might or might
not be interpolable?  We should have the same behaviour, if so.

> 2) At least one filter function pair is not of the same type.

Same question here.

> To 1): Is it possible to remove this restriction and animate all
> function pairs if they are of the same type even if we have a SVG
> Filter reference? What happens with the filter reference? In theory
> they could follow the animation model of enumerations that the CSS WG
> agreed on in Lyon. (Every time the transition function crosses 0.5 on
> output percentage, the value flips to either from- or to-reference
> depending on the derivation of the transition function.)

Sounds reasonable to me.

> To 2): Many filter functions (shothands) can be described by color
> matrices. Is there a way to interpolate between color matrices? I
> assume that it does not necessarily produce meaningful results, just
> like interpolation between matrix items on CSS transforms. Does
> anyone have experience on that?

I guess "meaningful" is open to interpretation.  It at least will let 
you see some continuous change in the filtered output.  There's still a 
good chance of it behaving unexpectedly, though.  Consider for example 
interpolating from 'hue-rotate(60)' to 'grayscale(0)'.  That will behave 
very differently from interpolating 'hue-rotate(0)', even though it has 
the same colour matrix as 'grayscale(0)'.

I don't think we can come up with a useful canonical decomposition (or 
maybe one at all?) like we do with transforms.