Re: [web-animations] Web Animations minutes, 8 / 9 Aug 2013

> > Animations from 0 to 0.25 or -0.25 should result in a
> > scale of 1.25 or 0.75, and one combining both should result in a
> > scale of 1. 

> Doug: I don't think this is a bug.
> 
> Perhaps this is an issue with the use of the term 'add' in 'composite: add', for transforms addition is defined as post multiplication.
> 
> This implies that 'zero' for scale addition is a scale of 1. So if you want to scale up a bit, then scale down a bit, you need to use 1.25 / 0.75, not 0.25 / -0.25.


It's not a bug. It is clearly explained in section 17 of the Transform spec. An additive scale of 2 and 0.5 combine to produce a scale of 1. An additive scale of 1.25 and 0.75 combine to produce a scale of 0.9375. I was expecting Core Animation behavior which I guess is normalized to produce my previous expectations. The updated scale test is:
http://jsfiddle.net/zQ6n3/3/embedded/result/

Thank you for not letting my own errors and misunderstandings negatively affect your opinion of the negative delta pattern.