Hi, I am fairly new to Inkscape and I am using it to create and alter patterns for scroll sawing. I want to create a spiral inside a shape, such as a heart, where the spiral takes the same shape. Something like the rough drawing below. Is there an easy way to do this?
Thanks,
Martin.

Hi Martin!

Challenging one.

I would draw that by single turns, then combine the paths together.
To draw one turn, the pattern along path extension/live path effect/bend live path effect would do the trick,
by bending a triangle.
Then repeat it on insets of the original path.

Hi.

From your illustration it looks like you are trying to make a "spiral heart"?
If yes, you are lucky, its easy to make spirals out of any shape you can describe by a mathematical formula.
Have a look at my guide for making heart shapes. viewtopic.php" onclick="readonly();return false;"http://www.inkscapeforum.com/viewtopic.php" onclick="readonly();return false;" class="postlink">http://www.inkscapeforum.com/viewtopic.php" onclick="readonly();return false;"https://dl.dropbox.com/s/xwerc28bqbwmvfq/ScrollSawHeart.png" class="postlink">

If you need assistance please chime back.

Good luck.
RGDS
Ragnar

Thanks for the replies.

Ragnar, I really ought to have stopped reading at the second line of your reply. My math education stopped at multiplication and division more than 50 years ago. Anything beyond that may as well be written in a foreign language.
I downloaded the guides, so if you hear a bang, or more likely, a pffffttttt, it's my brain exploding.

I replied to this on Saturday. I wonder if it got stuck in moderation somewhere. I don't want you two guys to think it was a post and run.

I'm wondering if you could use a "spiral heart" as described by Ragnar -which is very nice and clever nevertheless.
Isn't there a minimal width limit in the scroll saw technic?
That would need an Archimedean spiral, instead of a Logarithmic spiral?
Just to prevent the piece from breaking into parts.

Hi

Haydut1200:
The multiplication and division will get you a long way! Hopefully your brain has not exploded yet!
As Lazur Urh is pointing out the 'Logarithmic Spiral" might not be the way to go for making scroll saw patterns.

For a symmetric object the spiral might be the way to go but for un-symmetric objects like the heart another approach might be better.
A scroll saw extension might be the answer. Chime back if that's something that might come in handy.

Unfortunately my programming skills are at beginner level (as pointed out by some of the "pro's" on the forum when I made an earlier extension)
but I might give it a try nevertheless.

RGDS Ragnar

Hmm I was wrong about the Archimedean spiral, it doesn't seem to work either alone.


Also wrong with the insets too.
Simple insets cannot handle sharp inner corners of the path.
So it seems first you would need to figure out how each "parallel" heart shape should look.

Now I'm thinking of some 3D touch -modelling a heart shape and then drawing some of it's iso-lines
to have a base for each single turn.

Another try:



Made this with pattern along path live path effect.
The insets are the result of an interpolation, which, is still not the best.

Another try:


Now realising that it would be better if it didn't have even turns, ending the line at the right side.

The conception is still the same: create a "centerline" of the object, then use the interpolation tool to create "parallel" lines inbetween, then pattern along path live path effect on the right paths.

A centerline extension would be a good start for automating the drawing of such shapes.

I suppose it would help if I explained what is intended with this. The idea is to make a bowls of different shapes, not just a heart. The idea is to cut along the line at an angle of somewhere around 4 to 7 degrees so that the spiral can be pushed down and lock on it's own taper to form a bowl or basket. Hopefully the photo below explains it better, although I'd guess this one has been cut with laser.

A-ha!

So how much turns that mean, and how thick the spiral part should be compared to the overall shape?

I'm not sure that it matters how many turns there are. A circular bowl I made recently had about 5 turns in a 10cm diameter, with a 5cm dia bottom. Allowing for width of cut, the spiral would be about 4mm wide. Thickness of wood was 16mm. Angle of cut depends on wood thickness and also blade thickness and type, so a practice cut usually has to be made first.

Apologies for late reply.

Turns matter as how you want to connect the outer edge with the bottom part.
I constructed a heart's bottom, from now on it is more of manual working, repeating the same actions if such details are decided.
The photo example shows about 10-11 turns, you mentioned 5.

Here are the steps of the construction, in true scale:



The seventh row shows a comparision between a simple interpolation of the original paths, and how if the two had their nodes adjusted to each before the interpolate extension.

The last row has that two edge's nodes perfectly matching, so they can be used to produce parallel lines, as a basic for the spiral.

Here is how it could be finished to be a spiral with four and a half turns:



A bit thinner than 4mm, maybe it should all be scaled up a bit.
Also, by pussing the bottom part down, it will add a small rotation to the inner parts, and possibly it needs improvement on that.

haydut1200 wrote:...Is there an easy way to do this?...

Not that easy/quick, but I'm hoping some could understand the construction and it helps you.

Hi Lazur Urh.

Nice method!
Without an explanation of the steps it might be hard for a beginner to duplicate?

RGDS
Ragnar

Thank's Ragnar!

Exactly. And providing explanation would cover half of the manual.
Will try to explain any parts unclear, after recharging my brain cells with some sleeping.

Going in the rows order, from starting post:

1. After plotting a "pefect heart" as described by Ragnar with 100 samples, made three duplicants: one scaled to 100 mm in width, one 100 mm in height, and went along the middle one, the one that has the sizes the average of the two.
   Relatively high sample count will be good later on with the extensions used.
   
   Size can be either calculated or be constructed graphically.
   -Use the align and distribute panel to align the two shapes at the sides together at their edges next to eachother, group them together (Ctrl+G) and scale the group down by 50%, then change the size dimensions back to mm and copy the right width values for proportional scaling the original shape.
   
2. Finding an approximation of the center line.
   Added a stroke to the path through the fill and stroke panel (Shift+Ctrl+F), and thickened the stroke width until the two side's edge were touching.
   
3. The size description "about 5 turns in a 10cm diameter, with a 5cm dia bottom" meant to have thepreviously set stroke width divided by two.
   25 mm turn, 50 mm bottom, 25mm turn --->quarter, half, quarter divisions should have been used.
   
   At the top cusp node of the heart shape, the used method wouldn't provide a nice turn, so some space was was used:
   added a 0,833 mm stroke to the original path, and made the duplicant's outline thicker with that value too.
   
4. Outlines were converted to paths (Ctrl+Alt+C),
   broke apart (Ctrl+Shift+K).
   
5. The inner rounded corners removed.
   Next few steps are showing how the bottom part's top corner was made.
   
6. Corner part is better to be out of that blue quarter circle, and would look better if it was parallel to the line segments below.
   The svg also shows an early interpolaion used between the outer and inner paths.
   One of them uses the original paths, the other that was made after the originals nodes could be paired on an ortogonal line.
   
7. Comparision between the previous two.
   
8. Increasing the bottom path's duplicant's outline until it is tangent to the circular part, in search of a path which nodes can be paired with the original outline.
   
9. Outlines converted to paths.
   
10. Used the extrude extenson to show which nodes can be paired right.
    After the extension run with polygon option, the group was coloured by setting a red fill colour with no alpha values, no outlines, then
    ungrouped (Ctrl+Shift+G), went over with the tweak tool with colour mode, changing only the hue values, then grouped the object back together (Ctrl+G), and the opacity lovered.
    
11. Steps below: drawing the top corner and adjusting their nodes.
    Actually made a mistake by cutting the top part right at the middle, for making it spiral-like, it is better to have it a bit longer.

For the following post:

1. Result of the previous constructions, showing how the nodes of the two paths are matching, just as described previously.
   
2. Extending the top and the bottom lines with a small segment. It wouldn't had to be done if those were not cut off before.
   Added rectangle to the background for alignment reasons, and a triangle with isosceles that is used for the pattern along path live path effect later.
   
3. Interpolated between the two sides with the interpolate extansion.
   Each line are representing a half turn, thus made the double number of the turns.
   
   Once the it was done, the objects were grouped with a duplicant of the background rectangle,
   mirrored, and placed with the align and distribute panel.
   
4. Every second line is deleted, to make up the core paths of the spiral.
   
5. Adjusted the start and end nodes of the paths.
   The spiral transition was added by a pattern along the paths, making it necessary to start the paths exactly where the triangle's vertice will be at. The other end should be longer, to overlap the pattern at the corner.
   
   The pattern along path live path effect was set with the triangles pasted in after they were copied.
   Removed the outlines, changed fill, reversed paths on the right side,
   changed to outline mode (Ctrl+5 on the numpad twice).
   and adjusted the width of the sample, until they intersected right at the middle, above the rectangle's side.
   
6. objects were converted to paths, and the unnecessary segments unconnected and nodes deleted.
   To make it faster, two segments were removed, then the path was broken apart, and the unecessary path deleted.
   
7. Paths were combined together.
   
8. Double nodes were removed.

So this is how it was made in a nutshell.

Thanks for taking the time with this, though it's far beyond my capabilities with Gimp at the moment. I'll keep coming back to it as I learn more about Gimp, but at the moment my best bet is to try to make one from your last image. If I am successful, I'll come back with a photo of it.

Thanks,
Martin.

haydut1200 wrote: though it's far beyond my capabilities with Gimp at the moment.

Errr, obviously I meant Inkscape.