Filling arbitrary shape

Michael Borcherds shared this question 8 years ago

Here's a nice :question: trick using locus to fill an arbitrary shape :D

https://ggbm.at/549439

1

Hi Noel,

arbelos is a bit tricky indeed :)

//it's necessary to have the arcs/segments oriented in the same way, you can achieve it via Reflect[arc,line] as in attached file.

Also some types of arbelos should be now drawable via Reflect[Polygon[A,B,C],x^2+y^2=1]

https://ggbm.at/549441

1
1

Some time ago, try the same, solved using polygons the lists and , unlike the method given by murkle, this latex export code is easier to read and modified, but, your are Master , to easy filling (no need polygon).

saludos

1

hello

sorry, the method is incredible and marvelous but...

when the point C is moved at extreme of the diameter in arbelos2.ggb file the filling shape gets an error

some months ago i tried it with arc of parabola and the work had the same problem

I did not get it

saludos

BTW: workaround defining a sub-segment "b" in segment "a" with very near extremes to extremes of "a"

1

This is really fantastic. :D

However, I found something weird and maybe it's worth taking a look at.

Regards,

Pegasus Roe

*edit: sorry, forgot to attach the file. :)

https://ggbm.at/549455

1

here is a file I'd like to share with everyone. :D

https://ggbm.at/549453

1

Since 360°=0, the arcs become undefined, but for some reason if c is undefined, {c} is defined and contains the last value of c. Thanks for report.

EDIT: fixed this for next release: arcs that are undefined will be treated correctly.

1

Since 360°=0, ...

I was just wondering why we can't have sliders with angle values ranging from -360° to 360°. :(

Now I know why. We all know that 360° and 0 point to the same direction on the plane, but 360°=0 is logically wrong. :cry:

If 360°=0 were right, then 180° = 360°/2 = 0/2 = 0 would be right too, and this definitely will be a disaster, ... em, I mean at least it broke my code ... :laughing:

Why does GeoGebra restrict itself to 0° and 359.99...° anyway :question: Is there a reason?

Regards,

Pegasus Roe

1

For "arbalos"(arc), séquences could be used to color them

Daniel

1

hello,

thanks pegasusroe I managed it, but before there was a flood of color on the three regions here is the attached file.

regards,

however, I dont understand is that a command or tool border={}

Files: 10.JPG
1

however, I dont understand is that a command or tool border={}

in case you guys are wondering why the above post pops up here, please see the discussion between maherom and me.

@maherom

border={a,b,c}

When you are trying to fill a closed curve consisting of some paths, it is very important to keep in mind that those paths MUST BE ORIENTED IN THE SAME DIRECTION.

for example, the following is correct:

but this one is wrong:

You can investigate the attached file if you want to.

https://ggbm.at/549505

1

hello,

thank you pegasusroe for this comment "it's a good observation".

regards,

1

The «Archimedes Salinon».

To orient the arcs just reflect on the bisector of the endpoints.

and the file:

Saludos

1

Hi all,

It is very "painful" that Semicircles (since the beginning of GGb) are not oriented in the trigo sense

Point[{Segment[A, B], DemiCercle[C, B], Segment[C, D], DemiCercle[A, D]}]

Totally agree, would be a good idea to implement the reverse option for CircularArc (default counterclockwise)

CircularArc[ <Midpoint>, <Point>, <Point> ,r]

where r (clockwise) is the arc symmetry respectively PerpendicularBisector of the end points

And other

«The cross of Malta»

and the file

Saludos

Files: cruz.jpg
1

Hello noel, a question, such as turning the locus around a point?, Is able to make a reflection or translation of this through lists?

I've tried, but I have not succeeded

many greetings

1

Hi!

What about to create a default tool to fill arbitrary shapes (encapsulating all steps described by Murkle)? Something like:

FillShape[list1]

where list1 is a list of curves (the boundary of the shape).

Humberto.

1

Here's a nice :question: trick using locus to fill an arbitrary shape :D

I think there is a problem with this method.

I created a locus using this method, and the outline looks correct, but when I shaded it the region is not as expected.

Please look at the attached file and see if you agree:

https://ggbm.at/552325

1

Tom,

Unfortunately Circular arcs cannot be used in this case. The "border" of the path must be continuous for this locus method to work. See the last post from pegasusroe above. Circumcircular arcs can used instead.

Simon

1

I can't find any good videos on how to make arbitrary filling work. Can you help?

1

I was hoping there would be a video with explanations. I dont get the "point2 = point1 + (0,0)"-part for example.