Interpolation Extension Bug ?

Raspi · Postby **Raspi** » Wed Nov 22, 2017 12:20 am

I have a square, converted to a path.
I add 4 nodes with the Node Tool rubberband selected and hitting the plus in the toolbar, so i end up with an 8 node square.

My original square is black, i duplicate and make it white.

Now i want a gradient of grays so i use the Interpolation Extension, with the "Interpolate style" option ticked.
I want 19 steps.

After the interpolation my squares have 9 nodes with "Interpolation Method 1" and 16 nodes with "Interpolation Method 2".

Anybody else experiencing this ?

tylerdurden · Postby **tylerdurden** » Wed Nov 22, 2017 2:02 am

I only see one square with 9 nodes. The others have a variety 15, 16...

I don't know if I'd call it a bug... It's not cloning.

You could use clones and shift the luminance value.

Raspi · Postby **Raspi** » Wed Nov 22, 2017 8:03 am

tylerdurden wrote:I don't know if I'd call it a bug... It's not cloning.

I dont know what exactly happens when the Interpolation is calculated, but why would it modify two identical paths, when its clear that only the colour is the difference ?

Thats like, not calling it a bug when Gaussian Blur suddenly turns the colour of the object into something else.
In the context of what i wanted to do, the Extension is destroying my path, and make my intended workflow impossible.

One of the problems with Inkscape is that there is always a specific way to get to a certain result, because the tools behave weird or unexpected, and it takes ages to find the correct one.
Its very frustrating.

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EDIT: i experimented a bit.
Tried a 2 node path. It interpolated okay from black to white, without adding more nodes. No complaints here.

Tried a star. Both same colour. It added a node so that you get an open path.

Tried a square. Both same colour. Again, it added a node, making the shape into an open path.

Tried a circle. Both same colour. It adds a node and makes the inbetween circles into slightly wonky, non round shapes.
Wtf.

EDIT 2:
Also tried with IS 0.48 portable.
Same results. The same open paths, the same increase in nodes with method 2.
Just a bit faster.

So it seems this behaviour was always like this and probably not a bug.

Moini · Postby **Moini** » Wed Nov 22, 2017 10:57 am

The 'open path' part is a known bug, I think. Just tested with master, it's even worse there - I get each node duplicated PLUS an open path.

flamingolady · Postby **flamingolady** » Thu Nov 23, 2017 3:47 am

Yes, I see that it has added duplicated nodes on top of each other, esp on your right side version- this has been happening to me since v 91. When you delete the extra node(s), then the path opens. It's not just in interpolation, it's all over the place when I chg to a path. I used power stroke to make a font and it just about drove me up a tree, almost to the point where it would take less time to not use it. To attempt a workaround, I would suggest that you use as few nodes to start with, use just 4 nodes. Also instead of starting with a square object, which you then have to convert to a path, draw your own square with the bezier tool, that way there is no converting to a path, so no dupped nodes. (Hint, to get it straight and sized, use your old square as a template, ie, chg the color, then draw your square on top of it).

Raspi · Postby **Raspi** » Thu Nov 23, 2017 7:31 am

Moini wrote:The 'open path' part is a known bug, I think. Just tested with master, it's even worse there - I get each node duplicated PLUS an open path.

Well, this is kind of comforting.

flamingolady wrote:I would suggest that you use as few nodes to start with, use just 4 nodes. Also instead of starting with a square object, which you then have to convert to a path, draw your own square with the bezier tool, that way there is no converting to a path, so no dupped nodes.

Unfortunately that wasnt an option with what i intended to do.
I found a different solution in the mean time.

Its just this often very time consuming quest for the do-able way that turns me off.
A tool is supposed to do a certain thing and if it doesnt, it gets complicated.

TBH, after all this, im not even sure what the Interpolation Extension is good for.

tylerdurden · Postby **tylerdurden** » Thu Nov 23, 2017 11:30 am

Raspi wrote:TBH, after all this, im not even sure what the Interpolation Extension is good for.

I use it for making laurels:

Extra nodes are not a problem in this case. YMMV

Raspi · Postby **Raspi** » Thu Nov 23, 2017 11:00 pm

tylerdurden wrote:
Raspi wrote:TBH, after all this, im not even sure what the Interpolation Extension is good for.

I use it for making laurels

I've done that as well and it works, no doubt.

Lets say i need 10 squares with 8 nodes each, going from desaturated orange to sky blue and i dont want any complicated math (tiled clones *cough*).

I could clone a column or arrange 8 duplicates by hand for the shapes, but for the colours its getting a bit complicated.
I could interpolate the gradient and transfer them by hand with the dropper tool but its a bit tedious.

Maybe interpolate colour attribute in a group extension ?

: rect862.png (1.21 KiB) Viewed 4294 times

tylerdurden · Postby **tylerdurden** » Thu Nov 23, 2017 11:43 pm

Maybe the trace feature of clones?

Raspi · Postby **Raspi** » Thu Nov 23, 2017 11:46 pm

tylerdurden wrote:Maybe the trace feature of clones?

Interesting !

tylerdurden · Postby **tylerdurden** » Thu Nov 23, 2017 11:48 pm

Funny how when the clones are adjacent, they look like they all have gradients... but they are truly solid colors.

Raspi · Postby **Raspi** » Thu Nov 23, 2017 11:54 pm

tylerdurden wrote:Funny how when the clones are adjacent, they look like they all have gradients... but they are truly solid colors.

I noticed that too

tylerdurden · Postby **tylerdurden** » Thu Nov 23, 2017 11:58 pm

Looks like a bug where the clones indicate a 1px stroke, but there are none when the links to original are broken. :-/

flamingolady · Postby **flamingolady** » Fri Nov 24, 2017 2:04 pm

Tylerdurden, thx for that tut of tracing, I could not have imagined that for the life of me. I've used interpolation alone to get the gradient look, but never the tracing feature. Amazing. thanks much

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