Re: Matrix Multiplication bug and workaround
On 07/30/2017 04:42 PM, hh via use-livecode wrote: Let me explain that a bit simpler for readers who don't know or forgot linear/matrix algebra. Thanks. That does make sense, and I did indeed need a refresher course. -- Mark Wieder ahsoftw...@gmail.com ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Matrix Multiplication bug and workaround
I noticed the announcement of your conference in Livecode website: https://livecode.com/global/hermann-hoch/ Have you checked Jim Hurley stacks? http://jamesphurley.com/Revolution.html Al > These were the first two minutes of my talk > at LC Global in Nov 2017.Now I can start after that, > describing how to find that single set, without > matrix algebra ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Matrix Multiplication bug and workaround
Hi Al. Yes. I saw this mistake several times. The misleading thing is, TMHO, the name "transformation matrix" for [a,b,c,d,e,f] (because the listing is pairwise for columns, as you now describe, and not for rows). Let me explain that a bit simpler for readers who don't know or forgot linear/matrix algebra. It would be better to name it, what it is, a "transformation list". [a,b,c,d,e,f] lists the factors [a,b,c,d] and the summands [e,f] that define the "affine transformation" of a point (x_old,y_old) to a point (x_new,y_new): x_new = a*x_old + c*y_old + e y_new = b*x_old + d*y_old + f [a,d] are the scaling factors for (x_old,y_old), [b,c] are the shearing factors for (x_old,y_old), [e,f] are the translation summands for (x_old,y_old). So [1,0,0,1,0,0] defines the identity: x_new = x_old and y_new = y_old. Every scaling, shearing, translation or rotation of a point (x_old,y_old) can be built by ONE single set of such a list [a,b,c,d,e,f]. Hermann p.s. These were the first two minutes of my talk at LC Global in Nov 2017. Now I can start after that, describing how to find that single set, without matrix algebra ;-) ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Matrix Multiplication bug and workaround
Hi Hermann, Hermann wrote: > This is not a bug, your script is wrong. > If TM is a,b,c,d,e,f then you have to d > put item 1 of pArgs into tMatrix[0,0] > put item 2 of pArgs into tMatrix[1,0] > put item 3 of pArgs into tMatrix[0,1] > put item 4 of pArgs into tMatrix[1,1] > this yields correct results. > [In fact your 'workaround' corrects the wrong script part] Now I understand: This transformation matrix: 1,0.6,-1.2,1,40,10 should be stored like this: [0,0] [0,1] [0,2] a c e 1-1.2 40 [1,0] [1,1] [1,2] b d f 0.6 1 10 [2,0] [2,1] [2,2] 0 0 1 I will delete my bug report. Thanks again Hermann for taking a close look at this. Have a nice week! Al ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Matrix Multiplication bug and workaround
Al, your script is wrong. You are building the matrix in a wrong way. It is no bug! With your 'workaround' you point yourself to the lines where you did make the mistake. http://lists.runrev.com/pipermail/use-livecode/2017-July/240074.html ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Matrix Multiplication bug and workaround
After searching the Mail List archives, the Forum and LiveCode Quality Center for another report about this bug, I found nothing and have just send a new bug report: http://quality.livecode.com/show_bug.cgi?id=20208 Al ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Re: Matrix Multiplication bug and workaround
Hi Al. This is not a bug, your script is wrong. If TM is a,b,c,d,e,f then you have to do put item 1 of pArgs into tMatrix[0,0] put item 2 of pArgs into tMatrix[1,0] put item 3 of pArgs into tMatrix[0,1] put item 4 of pArgs into tMatrix[1,1] this yields correct results. [In fact your 'workaround' corrects the wrong script part] Hermann ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
Matrix Multiplication bug and workaround
Using LC 8.1.3, I just found a bug in the Matrix Multiply function. Could you check if this bug was fixed in more recent versions of LC? Follow this recipe to reproduce this bug: 1) Create a new stack with a button, a text field and a check box named "showbug" 2) paste these two lines into the text field: TM 1,0.6,-1.2,1,40,10 CO 0,30 You could find this and other examples in this webpage: https://stackoverflow.com/documentation/svg/3249/transformation#t=20170730054300495488 3) paste this script into the button: local tMatrix1 local tMatrix2 on mouseUp put empty into tMatrix1 put empty into tMatrix2 put empty into tNewMatrix put empty into tNewCoordinatePoint put fld 1 into tMatrixList repeat for each line tMX in tMatrixList switch word 1 of tMX case TM TransformTMatrix(word 2 of tMX) break case CO CoordinatePointMatrix(word 2 of tMX) break end switch end repeat put matrixMultiply(tMatrix1, tMatrix2) into tNewMatrix combine tNewMatrix with comma answer item 1 to 2 of tNewMatrix end mouseUp on TransformTMatrix pArgs local tA local tB local tC local tD local tE local tF local tMatrix if the hilite of btn "showbug" then put item 1 of pArgs into tA put item 2 of pArgs into tB put item 3 of pArgs into tC put item 4 of pArgs into tD else -- use a workaround put item 1 of pArgs into tA put item 2 of pArgs into tC -- change position put item 3 of pArgs into tB -- change position put item 4 of pArgs into tD end if put tA into tMatrix[0,0] put tB into tMatrix[0,1] put tC into tMatrix[1,0] put tD into tMatrix[1,1] if (the number of items in pArgs) is 6 then put item 5 of pArgs into tE put item 6 of pArgs into tF else put 0 into tE put 0 into tF end if put tE into tMatrix[0,2] put tF into tMatrix[1,2] put 0 into tMatrix[2,0] put 0 into tMatrix[2,1] put 1 into tMatrix[2,2] if tMatrix1 is empty then put tMatrix into tMatrix1 return empty end if end TransformTMatrix on CoordinatePointMatrix tArgs put item 1 of tArgs into tG put item 2 of tArgs into tH put tG into tCoordinatePoint[0,0] put tH into tCoordinatePoint[1,0] put 1 into tCoordinatePoint[2,0] if tMatrix1 is empty then put tCoordinatePoint into tMatrix1 return empty end if if tMatrix2 is empty then put tCoordinatePoint into tMatrix2 return empty end if end CoordinatePointMatrix 4) Hilite the check box "showbug" and click the button... the result is 58,40 This result is wrong. 5) Unhilite the check box "showbug" and click the button... the result is 4,40 This result is correct. If this bug is still present in more recent LC versions. Could you report it to the Quality Center? Thanks in advance! Al ___ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
