Re: Forward direction
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On Tue, September 25, 2012 11:08 pm, Steve Thomas wrote:
> Edward, > > I think you may have uncovered a bug (although it may exist in the model > inside my head). Misfeature, I think. It doesn't break anything, but is only a design error. > I can take a polygon from the Supplies flap and it starts out with its > heading and forward direction as 0. > Then if I first change the forward direction to 180 and then change the > heading to 0 (which also changes the forward direction to 0) I wind up > with > the polygon costume turned 180, but heading and forward direction both 0. Exactly so. I'll add that point to the manual. Also the term costume. I like that. > This does not make sense to me. > > Also the Balloon help for "heading" states: "Which direction the object is > facing. 0 is straight up" Definitely uninformative. The important fact is that heading is the direction in which the object will move. > The Balloon help for "forward direction" states: "The angle of my forward > direction without rotating myself" Definitely meaningless. > Okay, so I may be starting to get this but it seems harder than it should > be. > > To my simple mind, there are two things: > > 1. the rotation of the costume, where its "original" value is 0 (ie: > straight up) (Seems like this should map to "heading" but my case above > provides a counter example. > 2. the "forward direction" which is the direction it will move in. You have it backwards, which does not surprise me in the confused state of the help and the documentation. > Thus changing forward direction should not IMNSHBOWO change heading. > Of course at this point we probably do not want to change existing > behavior > which could break old projects. So we may have to document as is. I'll do my best. > Stephen > IMNSHBOWO - In My Not So Humble But Often Wrong Opinion > > > On Tue, Sep 25, 2012 at 7:08 PM, Edward Mokurai Cherlin < > [hidden email]> wrote: > >> On Tue, September 25, 2012 12:56 pm, karl ramberg wrote: >> > On Mon, Sep 24, 2012 at 8:49 AM, Edward Mokurai Cherlin >> > <[hidden email]> wrote: >> >> >> forward direction: What effect or use does it have? >> > >> > Each player has a direction arrow that can be changed by clicking on >> > it while holding shift. >> > If it's not visible you can check the box 'direction arrow' in halo >> menu. >> > When you tell a player to move forward it will move in the direction >> > of the arrow. >> >> This turns out not to answer the question I asked. You are describing >> the heading, not the forward direction. >> >> Objects move in the direction of their heading, which is the direction >> of the Halo arrow, but not necessarily the same as the forward >> direction. Rotating the Morph with the Rotate handle in the Halo >> changes the heading but not the forward direction. Turning on the >> direction arrow, and then grabbing it with a shift-click and turning >> it, changes both the forward direction and the heading. These two >> values can be edited in the viewer as well. Editing the heading leaves >> the forward direction unchanged. Editing the forward direction also >> changes the heading. The command Object forward by 5 moves the Morph >> in the heading direction. I see nothing in Etoys that makes use of the >> forward direction. >> >> In Squeak, we see for the Morph class: >> >> heading >> "Return the receiver's heading (in eToy terms)" >> owner ifNil: [^ self forwardDirection]. >> ^ self forwardDirection + owner degreesOfFlex >> >> forwardDirection: newDirection >> "Set the receiver's forward direction (in eToy terms)" >> self setProperty: #forwardDirection toValue: newDirection. >> >> degreesOfFlex >> "Return any rotation due to flexing" >> "NOTE: because renderedMorph, which is used by the halo to set >> heading, goes down through dropShadows as well as transformations, we >> need this method (and its other implems) to come back up through such >> a chain." >> ^ 0.0 >> >> and so on. >> >> Also in Squeak, I see 19 senders of forwardDirection in 12 classes, >> which I do not feel ready to explore until after I learn rather more >> Squeak and Smalltalk. I can feel it coming on. ^_^ -- Edward Mokurai (默雷/निशब्दगर्ज/نشبدگرج) Cherlin Silent Thunder is my name, and Children are my nation. The Cosmos is my dwelling place, the Truth my destination. http://wiki.sugarlabs.org/go/Replacing_Textbooks -- Edward Mokurai (默雷/निशब्दगर्ज/نشبدگرج) Cherlin Silent Thunder is my name, and Children are my nation. The Cosmos is my dwelling place, the Truth my destination. http://wiki.sugarlabs.org/go/Replacing_Textbooks _______________________________________________ etoys-dev mailing list [hidden email] http://lists.squeakland.org/mailman/listinfo/etoys-dev |
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