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Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

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Edward Mokurai Cherlin

Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

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
_______________________________________________
etoys-dev mailing list
[hidden email]
http://lists.squeakland.org/mailman/listinfo/etoys-dev

Steve Thomas

Re: Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

Edward,

I think you may have uncovered a bug (although it may exist in the model inside my head).

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. This does not make sense to me.

Also the Balloon help for "heading" states: "Which direction the object is facing. 0 is straight up"

The Balloon help for "forward direction" states: "The angle of my forward direction without rotating myself"

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:

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.
the "forward direction" which is the direction it will move in.

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.

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
_______________________________________________
etoys-dev mailing list
[hidden email]
http://lists.squeakland.org/mailman/listinfo/etoys-dev

_______________________________________________
etoys-dev mailing list
[hidden email]
http://lists.squeakland.org/mailman/listinfo/etoys-dev

Steve Thomas

Re: Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

Other interesting thing is that if you turn by 270, heading=-90 and forward direction=270

Why? Well on the one hand good to think of things using multiple models, but still.

Also one other thing that affects rotation (although only for "graphics" (stuff you paint or images imported) is "rotation style" which now that we have "flip left rignt" and "flip up down" perhaps should be removed from the Etoys friendly mode.

Rotation Stye has four options:

rotate (turns as you would expect, default behavior)
flip left right - flips costume when heading >180 *except for cases where you change forward direction and it can flip with heading = 0"
flip up down - same as above only up down transformation
do not rotate - self explanatory

Stephen

On Tue, Sep 25, 2012 at 11:08 PM, Steve Thomas <[hidden email]> wrote:

Edward,

I think you may have uncovered a bug (although it may exist in the model inside my head).

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. This does not make sense to me.

Also the Balloon help for "heading" states: "Which direction the object is facing. 0 is straight up"
The Balloon help for "forward direction" states: "The angle of my forward direction without rotating myself"

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:
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.

the "forward direction" which is the direction it will move in.

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.

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
_______________________________________________
etoys-dev mailing list
[hidden email]
http://lists.squeakland.org/mailman/listinfo/etoys-dev

_______________________________________________
etoys-dev mailing list
[hidden email]
http://lists.squeakland.org/mailman/listinfo/etoys-dev

Bert Freudenberg

Re: Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

On 2012-09-26, at 05:08, Steve Thomas <[hidden email]> wrote:

changing forward direction should not IMNSHBOWO change heading.

Wrong indeed ;) It's actually quite simple:

Forward Direction describes where "forward" is in the graphic shape of an object, whereas "heading" describes the object's rotation. If you paint a car from the top, then "going forward" should mean going "up" on the screen. If you paint a fish pointing right, then "going forward" should mean going "right". Now what's the difference between these two objects? It's just an image. The computer can't tell. So we have to tell it, leaving the car's forward direction at 0 degrees (meaning "north"), but changing the fish's forward direction to 90 degrees ("east").

Example. Here's a fish, freshly painted:

Telling it to move forward would move it up the screen. Not what we want. So we shift-drag the green forward-arrow to point to the fish's "nose":

So now the forward direction is to the right. The appearance of the fish did not change, but since going forward now would move it in another direction, its heading has changed, obviously. Afterwards we can change the heading, of course, which rotates the object as expected:

And so on:

Note that if we had *not* changed the heading value when dragging the forward arrow, *this* is the picture we'd have gotten. Not good.

One way to think about it is that the forward direction describes the rotation as seen from the inside of the object, and heading is the rotation as seen from outside. You almost never have to use the numerical value of the forward direction because it only describes in which orientation the object was painted.

HTH,

- Bert -

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Bert Freudenberg

Re: Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

In reply to this post by Steve Thomas

On 2012-09-26, at 05:08, Steve Thomas <[hidden email]> wrote:

> Edward,
>
> I think you may have uncovered a bug
>
> I can take a polygon

Polygons are very special. You could have used almost any other object. The preferred means of creating an object in Etoys is by using the paint tool.

> 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. This does not make sense to me.

This is because polygons are not rotated like other objects. When rotating a polygon, its vertices get changed. The new heading is recorded in the polygon's forward direction. That means that for polygons, heading and forward direction are intrinsically linked, unlike for any other object where they are independent.

The reason polygons are different is so that they do not get magnified like a sketch when resized, but they keep their border width.

One way to think of it is this: when an object's forward direction is the same as its heading (+/- 360 degrees) then its screen image appears unrotated from its "intrinsic" image. That's always the case for polygons because rotating the polygon changes its internal orientation, whereas for sketches the original sketch is not modified so it needs to keep track of the forward direction independently of its heading.

- Bert -

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Steve Thomas

Re: Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

In reply to this post by Bert Freudenberg

On Wed, Sep 26, 2012 at 9:02 AM, Bert Freudenberg <[hidden email]> wrote:

On 2012-09-26, at 05:08, Steve Thomas <[hidden email]> wrote:
changing forward direction should not IMNSHBOWO change heading.

Wrong indeed ;) It's actually quite simple:

Not the first or last time. The only thing good about being wrong is when I find out I learn something new! Thanks.

One way to think about it is that the forward direction describes the rotation as seen from the inside of the object, and heading is the rotation as seen from outside. You almost never have to use the numerical value of the forward direction because it only describes in which orientation the object was painted.

This is perhaps the best and simplest explanation yet.

HTH,

It definetly helps.

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Bert Freudenberg

Re: Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

On 2012-09-26, at 15:57, Steve Thomas <[hidden email]> wrote:

> On Wed, Sep 26, 2012 at 9:02 AM, Bert Freudenberg <[hidden email]> wrote:
>> On 2012-09-26, at 05:08, Steve Thomas <[hidden email]> wrote:
>>> changing forward direction should not IMNSHBOWO change heading.
>>
>> Wrong indeed ;) It's actually quite simple:
> Not the first or last time. The only thing good about being wrong is when I find out I learn something new! Thanks.
>>
>> One way to think about it is that the forward direction describes the rotation as seen from the inside of the object, and heading is the rotation as seen from outside. You almost never have to use the numerical value of the forward direction because it only describes in which orientation the object was painted.
> This is perhaps the best and simplest explanation yet.
>
>> HTH,
> It definetly helps.

Great! Maybe you could come up with better help balloons for these tiles ...

- Bert -

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[hidden email]
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Steve Thomas

Re: Forward direction (was Re: First draft of Etoys Reference Manual Glossary)

Created Issue in Tracker http://tracker.squeakland.org/browse/SQ-1117 cc'ing education team for input.

Change Baloon Help as follows:
"heading" - Which direction the object will move. 0 is straight up.
"forward direction" - Rotation of the forward direction arrow. This will not change when you turn the object.

or
"forward direction" - Rotation of the forward direction arrow relative to the costumes original orientation.

Stephen

On Wed, Sep 26, 2012 at 10:02 AM, Bert Freudenberg <[hidden email]> wrote:

On 2012-09-26, at 15:57, Steve Thomas <[hidden email]> wrote:

> On Wed, Sep 26, 2012 at 9:02 AM, Bert Freudenberg <[hidden email]> wrote:
>> On 2012-09-26, at 05:08, Steve Thomas <[hidden email]> wrote:
>>> changing forward direction should not IMNSHBOWO change heading.
>>
>> Wrong indeed ;) It's actually quite simple:
> Not the first or last time. The only thing good about being wrong is when I find out I learn something new! Thanks.
>>
>> One way to think about it is that the forward direction describes the rotation as seen from the inside of the object, and heading is the rotation as seen from outside. You almost never have to use the numerical value of the forward direction because it only describes in which orientation the object was painted.
> This is perhaps the best and simplest explanation yet.
>
>> HTH,
> It definetly helps.

Great! Maybe you could come up with better help balloons for these tiles ...

- Bert -

_______________________________________________
etoys-dev mailing list
[hidden email]
http://lists.squeakland.org/mailman/listinfo/etoys-dev

_______________________________________________
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