On Mon, Jun 2, 2014 at 3:19 PM, Rik Cabanier <caban...@gmail.com> wrote:
> isIdentity() indeed suffers from rounding errors but since it's useful, I'm > hesitant to remove it. > In our rendering libraries at Adobe, we check if a matrix is *almost* > identity. Maybe we can do the same here? > One option would be to make "isIdentity" and "is2D" state bits in the object rather than predicates on the matrix coefficients. Then for each matrix operation, we would define how it affects the isIdentity and is2D bits. For example we could say translate(tx, ty, tz)'s result isIdentity if and only if the source matrix isIdentity and tx, ty and tz are all exactly 0.0, and the result is2D if and only if the source matrix is2D and tz is exactly 0.0. With that approach, isIdentity and is2D would be much less sensitive to precision issues. In particular they'd be independent of the precision used to compute and store store matrix elements, which would be helpful I think. Rob -- Jtehsauts tshaei dS,o n" Wohfy Mdaon yhoaus eanuttehrotraiitny eovni le atrhtohu gthot sf oirng iyvoeu rs ihnesa.r"t sS?o Whhei csha iids teoa stiheer :p atroa lsyazye,d 'mYaonu,r "sGients uapr,e tfaokreg iyvoeunr, 'm aotr atnod sgaoy ,h o'mGee.t" uTph eann dt hwea lmka'n? gBoutt uIp waanndt wyeonut thoo mken.o w _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
