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Author Topic: cut up a circle  (Read 5569 times)

August 14, 2015, 11:19:50 PM
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kdresher

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I found tutorials to make shattered glass but I am looking to try to make a circle cut a portion off and be able to move that portion around, cut that portion up even more etc. want to use the free draw as I do not want need it to be straight cut.

August 15, 2015, 01:07:16 AM
Reply #1

brynn

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Welcome to Inkscape Community!

I'm not clear what you're asking.  Can you show us an example of what you want to do?

Are you asking for some kind of animation?
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August 15, 2015, 05:01:48 AM
Reply #2

kdresher

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circle.png
*circle.png
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the bottom corner I want to cut away like the duplicates to the right where I can cut that portion into even smaller pieces etc.

guess like how glass when it breaks on a fall pieces of it fly away from the rest of the glass.

August 15, 2015, 05:06:41 AM
Reply #3

kdresher

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I have one idea of using the handdraw and bezier tools and create individual pieces over the section I want broken up, but hoping for a quicker way of doing this.

August 15, 2015, 06:04:45 AM
Reply #4

brynn

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Oh, I understand much better now!

You could do it in just the same way as you did for the first piece.  But it sounds like you're asking for more of an automated way to do it -- like with an extension maybe.

Yes, I can image such an extension -- click "CRASH" button and the glass breaks automatically!!  I'm sure it's entirely possible for someone who knows about programming, to make something like that.  But I don't have those kind of skills.

I do have a couple of ideas, but I'm not sure if they will work.  So give me a few minutes to experiment, and I'll post back with some info   :wink1:
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August 15, 2015, 08:35:35 AM
Reply #5

Lazur

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You can try the eraser tool maybe.
Produces a slight gap, and after using it just break path apart (Shift+Ctrl+K).


There is no trivial solution of adding intersection points to B?zier paths as far as I know, maybe that's why such a "cad like feature" is being postponed that could produce zero width cuts.

August 15, 2015, 11:29:10 AM
Reply #6

brynn

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Well, it seemed like a quick write up at first, because I can see the main steps in my mind were just 4 or 6.  But writing them out took longer than I thought   :uhoh:

Ok, these may be a little more intermediate techniques, but it looks like you've already figured out how to draw, and maybe even edit paths.  Here's a tutorial to introduce you to the basics of path editing (sometimes called "node editing"):  http://forum.inkscapecommunity.com/index.php?action=articles;sa=view;article=7 if you need it.

Btw, can you give me a link to the glass shattering tutorial?  I think I know which one you mean, but I'm just curious.  And the steps I'm about to show are very different.  And they'll give a different effect too.  But this is the first thing that comes to mind.  It will give you the kind of pieces that you see if you shatter a car window (they're made on purpose to break into tiny pieces that aren't very sharp (compared to breaking a window in your house) to help reduce injury in car crashes).

Anyway, when I see that tutorial, maybe it will jog my memory, and I'll think of something better.

For this tutorial, I'm working on a piece about 100 x 100 pixels, so the values in the extensions will work good on that size.  Just so you know.  So your values may end up quite different from mine, depending on your needs and the size of your original piece.  Much later, I might write a more "official" tutorial, which would include illustrations and an SVG file.  But I don't have time for that right now.

1.  Select the smaller path that you want to break up
2.  Extensions menu > Generate from path > Voronoi Pattern
3.  Set both values there to 20
4.  Click Apply

Since I don't know exactly the sizes you'll need, you'll probably have to adjust those numbers.  For this, it's good to check the Preview box.  Then you can change the numbers and see what that change looks like, without having to Apply and Undo, over and over.  Note that it takes a few seconds for each change to happen (depending on your system).

So be patient, and when you get to something you like, click Apply button.  And then be sure to Save.  Working a lot with some extensions and most filters seems to invite slowdowns, freezes or even crashes sometimes (depending on your system), especially if you working quickly.  Well, at least it does for me -- but most advanced and expert Inkscape users agree that frequent saving is a good habit to develop  :wink1:

6.  Select it again
7.  Object menu > Pattern > Pattern to Object

It may seem to disappear, depending on your Inkscape preferences.  But look around your canvas, maybe zoom out, if you're all zoomed in. When you find it, you'll notice that the pattern fills the bounding box (dashed line rectangle) instead of the shape of the piece.  But don't worry about that now.

8.  Select it if it has come unselected
9.  Path menu > Break Apart

If it comes unselected from here, you'll have to select it by dragging out a selection box with the Selection tool  :sel:.  That's because now, the whole thing is made of a whole bunch of short paths segments, with only 2 nodes.

10.  Select the whole thing
11.  Extensions menu > Modify Path > Fractalize

You'll also probably want to use the Preview feature here, and experiment with different values.  Try starting with 3 Subdivisions and 1.0 Smoothness, and adjust from there.  For Smoothness, you can spin it below 1.0, for jagged-er pieces.  It will be tricky to see the results after you click Apply.  Read on --

12.  Click Apply
13.  Drag selection box around the whole thing
14.  Click the small X box at the far left end of the color palette, which is just below the canvas and above the status bar

Now you should be able to see the pieces.  And now it's time to start with the node editing.  Because they aren't really pieces  yet, even though it might look like some of them are - they are still just path segments.

15.  With the Selection tool  :sel:  drag a selection box, to select say 10 to 15 paths that are all close together.
16.  Press the 3 key, which will zoom your canvas so that the selection fills the canvas- it will make it easier to work on the paths
17.  Deselect and switch to the Node tool   :node:

18.  Select 2 paths which either touch each other, or that you want to connect to become 2 sides of the tiny piece
19.  If their end nodes already overlap, they are ready to connect --  If the end nodes don't overlap, drag them to where you want them to be
20.  Edit menu > Duplicate these 2 paths (or this button  :dup: on the command bar) (or key shortcut)

21.   Drag a selection box around the 2 end nodes that you want to join (note that they must be end nodes)
22.  Click "Join selected nodes" button  :jsn:  on the Node tool control bar (or look up the key shortcut in the Help menu)

23.  Select the next side that you want to connect
24.  Drag it's end node so that it overlaps with the end node of the other 2 sides
25.  Duplicate the new side path, before you join it the rest (this is very important, don't forget)
26.  Join the 2 nodes

Repeat #23 to #26 until you have 1 whole tiny piece finished.  When you finish 1 piece, you might want to temporarily give it some fill color.  That will make it easier to select or move around, later on.  If you don't give it some color,  you will quickly learn why it's helpful   :lol:

27.  Select the new tiny piece and Object menu > Lower to the bottom (or  :m2b: button on the Selection tool control bar)

Now moving on to the next piece.  Remember how you duplicated each side piece, before you connected it to the rest?  This is the secret for having the sides of one piece exactly match the side of the next, and all the way around!

Now continue with the same routine, steps #18 to #27, until you finish the next piece.  And continue until you have as many pieces as you need to.  If you want a larger area that isn't broken, you can just delete some of those individual paths.

When you finally have all the pieces that you need, you'll probably need the pieces along the outside of the original larger piece to conform to the shape of the original larger piece.  Easy to do!

1.  First, if you want any tiny pieces to be separated from the larger piece, drag those a short distance away
2.  Find your original larger piece and drag it to where all the tiny pieces are
3.  Move it on top of all the tiny pieces (this button on Selection tool control bar  :mtt: ) and make sure that it does not touch any of the tiny pieces that you want to be separated
4.  Drag a selection box around ALL the pieces except the separated tiny pieces
5.  Object menu > Clip > Set

Now there will be some tiny pieces that are still together and shaped like the original larger piece, as if that piece was cracked.  And there will be tiny pieces that are separated

So that should get you some shattered automobile glass appearance, something like the attached image below (except it will be in the shape of the original object).

I wish I had time to make this tutorial better with illustrations, but maybe I can spiff it up next month.



Please feel free to reply if you have any questions.  I do have plenty of time to answer questions (just not work up a full tutorial).  I probably made some mistakes, either in Inkscape steps, or typing mistakes.  So just let me know.   Or if no questions, let us know how it goes.

Good luck  :D

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August 17, 2015, 05:50:37 AM
Reply #7

bartovan

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I suppose this is the slow method that kdresher refers to (and is looking for a faster one), but actually if you use shortcuts it's not all that slow, I find:
- draw a circle, activate snap to path and draw a freehand "crack" over it. Thanks to snap, you can coincide perfectly with the circle's edges.
- with the crack still selected, duplicate it (Ctrl+D), shift-select the circle, then "cut path" Ctrl+Alt+/
- last step: duplicate the crack and combine with the two pieces of the circle. In long: duplicate the crack (Ctrl+D), shift-select one circle segment and do Path -> combine (Ctrl+K). Then select the remaining duplicate of the crack (you might need Alt+click to select underlying), shift-select the remaining segment of the circle, and Ctrl+K again. Done.

In exactly 6 key presses and 5 mouseclicks you have broken your glass in two. Which is not that bad, no? In case you want to manually draw your cracks...
(Suppose I don't say nothing new here, but anyway... And BTW the Voronoi stuff is very interesting, thanks brynn, I wouldn't have thought of that).



August 17, 2015, 07:10:14 AM
Reply #8

brynn

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Welcome bartovan!
Yeah, I guess it is "slow".  But there just isn't a magic button that will do it all at once.  The Voronoi pattern was the first thing that came to mind, but it still requires more editing.

If you take out the reading in between, these steps can all be done in 5 minutes or less.  It doesn't seem so slow to me.

OH!  I just thought of something.....  Using the Star tool with 10 or so spikes and some randomization, can make a sort of broken glass appearance, in a way.  I'm not sure how much realism the op wants.

broken-glass.png
*broken-glass.png
(45.57 kB . 753x398)
(viewed 1860 times)


With color

b-glass.png
*b-glass.png
(115.06 kB . 753x398)
(viewed 1053 times)
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August 17, 2015, 07:17:28 AM
Reply #9

brynn

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Could be clipped into a certain shape.
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August 17, 2015, 12:47:41 PM
Reply #10

Lazur

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Filtering may also work to generate a shattered pattern.