I'd like to check the curvature of a bezier curve, to see where there are unwanted curvature gradients. I found an article for AutoCAD where it explains using a "curvature comb", so you can see where there are discontinuities etc.
Yes, I probably expressed myself poorly with the continuity bit, I do use the first 3 node types. Also don't know what the "auto smooth" node does!
The curvature comb tool in AutoCAD let's you visualise the rate of change of the curvature, which is very useful for smoothly lofting boat hulls, wings, foils etc. Pity Inkscape doesn't seem to have this. I wonder if anyone has done an add-on maybe?
@doctormo I created one in another system that had an API to read the curvature at a given point along a curve. So my app did the following
Distribute points equally along the curve. User chooses Fine/Medium/Coarse spacing
At each point, read the curvature, create a normal line, length = the curvature x a scale factor.
User can increase/decrease the scale factor to suit. Including reverse the direction.
User can switch between Curvature and Radius (1/Curvature) display
Display local maxima and minima. If the curvature is higher on points on both sides of the one being analysed, set it's line colour differently. Essential to find flat spots or inflection points in the curve.
Mine isn't dynamic though. Which would be really useful for when tweaking the shape.
I imagine creating that in Inkscape is too difficult for me though.
It would require quite a bit of time and effort for sure. But with enough documentation in a ux issue/feature request, it could be given to a student or perhaps a future funded target.
I'm happy to create an issue with all the details and diagrams. Even if it doesn't end up getting used. However as I don't personally need it in Inkscape, we would need someone who needs to use the functionality, with all their use cases, to give some input and direction. And maybe something to show that it is wanted by more than one Inkscape user.
@TylerDurden Yes, in fact I've already tried to import SVG into Fusion 360 (Personal). I was a bit disappointed that the points in a curve cannot be moved once in F360, even though I tried importing as an SVG, and a DXF. Maybe that's because I've only been using Inkscape for 5 mths, and F360 for 2 wks, so lack of knowledge is probably a factor?
I'm just a hobbyist (and an old fart), but I like to create technical style drawings - old school like Elevation, End Elevation and Plan. These are usually derived from images I've grabbed of the sailing boats I'm interested in. I'm OK with using Bezier curves, although I should probably practise using less points than I instinctively do. These extra points do make it more difficult to adjust a curve if I didn't get it quite right from the start, which is why curvature combs would possibly help.
One other feature that I found very useful in F360 is the dimensioning of a drawing. In Inkscape I use a layer for these, but have to manually create them.
All in all though, I've found Inkscape really great to work with, and had a comparatively small learning curve. So I frequently recommend Inkscape on the sailing forums I haunt. 😊
FWIW... I finally worked out the difference between the Smooth node, and the "Auto-Smooth" node. Found that I had made life more difficult for myself by not studying this before - it's now heaps easier to smooth out an obvious (but minor) irregularity in a curve than before, by using Auto-smooth! 🙄
For any other beginners like me, an easy way to see and understand the difference of the nodes is:
make a rather irregular curve using half a dozen or so nodes, by just clicking (not dragging)
make a copy of this for comparison, move it down so you can see it separately & modify easily
on one curve select 3 adjacent nodes somewhere in the centre, and change them to Smooth, and on the other curve select the same 3 nodes but make them Auto-smooth
now move the middle one of those 3 nodes around a bit on each curve, and instantly see how they work differently 😊
Beginners' Questions Does Inkscape have a Curvature Analysis Tool
Inkscape.org
I'd like to check the curvature of a bezier curve, to see where there are unwanted curvature gradients. I found an article for AutoCAD where it explains using a "curvature comb", so you can see where there are discontinuities etc.
http://www.bluesmith.co.uk/LW/theoryBuilders/evaluateComb.htm
I've been searching for a while, but I haven't found any references to doing something like this so that curves can be "faired".
Inkscape has no tools to analyse or visualise the curvature of a path. However, the node tool can modify the path continuity.
Yes, I probably expressed myself poorly with the continuity bit, I do use the first 3 node types. Also don't know what the "auto smooth" node does!
The curvature comb tool in AutoCAD let's you visualise the rate of change of the curvature, which is very useful for smoothly lofting boat hulls, wings, foils etc. Pity Inkscape doesn't seem to have this. I wonder if anyone has done an add-on maybe?
A quick workaround is to import the SVG into Fusion 360. Then, the comb analysis can be applied.
Not real-time in Inkscape, but better than nothing. (Personal version is free.)
Sounds like a fun feature to add though.
@doctormo I created one in another system that had an API to read the curvature at a given point along a curve. So my app did the following
Mine isn't dynamic though. Which would be really useful for when tweaking the shape.
I imagine creating that in Inkscape is too difficult for me though.
It would require quite a bit of time and effort for sure. But with enough documentation in a ux issue/feature request, it could be given to a student or perhaps a future funded target.
I'm happy to create an issue with all the details and diagrams. Even if it doesn't end up getting used. However as I don't personally need it in Inkscape, we would need someone who needs to use the functionality, with all their use cases, to give some input and direction. And maybe something to show that it is wanted by more than one Inkscape user.
@TylerDurden Yes, in fact I've already tried to import SVG into Fusion 360 (Personal). I was a bit disappointed that the points in a curve cannot be moved once in F360, even though I tried importing as an SVG, and a DXF. Maybe that's because I've only been using Inkscape for 5 mths, and F360 for 2 wks, so lack of knowledge is probably a factor?
I'm just a hobbyist (and an old fart), but I like to create technical style drawings - old school like Elevation, End Elevation and Plan. These are usually derived from images I've grabbed of the sailing boats I'm interested in. I'm OK with using Bezier curves, although I should probably practise using less points than I instinctively do. These extra points do make it more difficult to adjust a curve if I didn't get it quite right from the start, which is why curvature combs would possibly help.
One other feature that I found very useful in F360 is the dimensioning of a drawing. In Inkscape I use a layer for these, but have to manually create them.
All in all though, I've found Inkscape really great to work with, and had a comparatively small learning curve. So I frequently recommend Inkscape on the sailing forums I haunt. 😊
@Ianp5a Well I'll put my hand up, useful for fairing compound curves when recreating hull profiles etc. But as an amateur, I don't think I count. 😄
@MaxHugen Take a look at B-Spline mode in the Pen tool. It makes drawing really smooth shapes less fiddly than the Bezier mode..
@MaxHugen >But as an amateur, I don't think I count.
Everybody counts Max! :-) Especially Inkscape fans who spread the word.
@Ianp5a Thanks Ian, will do. Haven't explored these yet.
FWIW... I finally worked out the difference between the Smooth node, and the "Auto-Smooth" node. Found that I had made life more difficult for myself by not studying this before - it's now heaps easier to smooth out an obvious (but minor) irregularity in a curve than before, by using Auto-smooth! 🙄
For any other beginners like me, an easy way to see and understand the difference of the nodes is: