This is normal and expected, but the docs should be clearer. setScale/setTranslate/etc. on Matrix set the Matrix to the specified transformation. To compose the transformation with the existing Matrix you need to use the pre/post methods.
On Sat, Apr 12, 2008 at 3:18 PM, Rui Martins <[EMAIL PROTECTED]> wrote: > > > The following Code works, and does what we expect: > > android.graphics.Matrix myMatrix = new android.graphics.Matrix(); > myMatrix.reset(); > myMatrix.setScale( 1, 1 ); > myMatrix.preTranslate( 100.0f, 36.5f ); > > This code, DOES NOT work, i.e. does NOT do what we expect > android.graphics.Matrix myMatrix = new android.graphics.Matrix(); > myMatrix.reset(); > myMatrix.preTranslate( 100.0f, 36.5f ); > myMatrix.setScale( 1, 1 ); > > I was able to spot the problem, because I was using myMatrix, to calc > an animation step, so small variations are easilly detectable, if they > don't occur. > > The Documentation states: > > public void setScale(float sx, float sy) > Set the matrix to scale by sx and sy. > > But Matrix setScale(...) method, is doing more than it should, i.e. > it's resetting the matrix translation parameters too, so any previous > translation info is lost. > > If we setScale(...) first and translate later, it works, because we > add the translation after the scale. > > However if we use preScale(...) or postScale(...) it works always as > expected. Although it's ane ntirelly different operation, since if the > matrix is already scaled, it will increase the scaling by Sx and Sy > factor. > > Apparently, the setScale(...), is resetting the matrix translation > parameters, most probably is doing something similar to setting the > Matrix to identity, and then set scale (Sx and Sy), i.e. it's probably > rewriting the entire matrix. > > This is NOT stated anywhere in the docs, and besides, is not what > anyone would expect! > > setScale(...) should only change the Sx and Sy parameters of the > Matrix, and leave the rest of the matrix untouched. > > Hope someone from google will confirm this. > > NOTE1: This is on M3. Haven't checked on M5 > NOTE2: There is another Matrix class in android.opengl.Matrix, maybe > it's scaleM(...) matrix, also has this problem, haven't checked > though. > > > > -- Romain Guy www.curious-creature.org --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] Announcing the new M5 SDK! http://android-developers.blogspot.com/2008/02/android-sdk-m5-rc14-now-available.html For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
