Re: [Inkscape-user] Cut segment from circle, extend bezier curves from cut points
Hi,
Can anyone suggest to the newbie a good way to make a stable, easily manipulated construction of the above curve in inkscape-cvs?
do you have a bitmap version of the logo online somewhere?
From your description alone it's hard for me to imagine what
the logo actually should look like (English not being my first language).
Claus
Claus Cyrny wrote:
Can anyone suggest to the newbie a good way to make a stable, easily manipulated construction of the above curve in inkscape-cvs?
Do you have a bitmap of the logo somewhere?
The logo resembles a concentric pair of 'G' characters, with a few flourishes. The task to break the circle, remove a segment of the arc and extend the endpoints with curves is roughly equivalent.
I worked late to figure it out in inkscape-cvs. The logo turned out well, considering it was my first inkscape document. The annotated steps were roughly as follows:
1. Make the circle as a shape.
2. Convert circle to a path.
3. Select two of the four control nodes, insert a node.
4. Inserted node will appear at midpoint on path between selected nodes.
6. Do not move any nodes yet, you'll damage path's circularity.
5. Repeat steps 3,4 recursively until you have a node close enough to your desired cut point at each side of the segment to be removed.
7. Select the desired cut node and 'cut path at node'. Repeat for other side.
8. Selecting the node of the cut segment can be difficult, since they share the same location as nodes on the preserved path. Use undo immediately if you select the wrong one. You definitely don't want to disturb nodes relating to the curvature of your circle.
9. Clean up extra nodes near the endpoints *before moving any*. I've found that you can often remove some of the intermediate nodes placed halfway between other nodes. Removal of a node will only be practical if there is enough weight available in the remaining nodes to replicate the original curvature. Ride the undo button immediately if you remove a critical node and lose curvature.
Based on the successful experience I had making this logo, and learning inkscape in general, I'd like to offer the following usability observations. The following would make this type of editing easier:
A. Selected control nodes should be more visibly indicated. Their selected status is hard to see.
B. There should be a keyboard shortcut to toggle a mode highlighting richer bezier info on the selected path. The user would see, node number 0..N, degree, etc. for each node, near the node. This would be used in enhancement D, among other places.
C. For multiple nodes sharing the same location, you should be able to keep clicking the spot to cycle through the various nodes, even if they're on different paths. This is probably a general 'drill-down selection' feature request, not just paths.
D. There should be some control over how far along the path between selected nodes the inserted node appears. A toolbar slider going from 0 to 1 would be ideal. The 0 end would be the lower-numbered selected node (i.e. nearer the start of the path), 1 the higher numbered node. Moving the slider to 0.25 would place the inserted nodes one quarter of the way along the path segment between the two selected nodes. This would save a lot of the recursive subdividing I had to emply in my logo.
E. The degree of each node needs to be more integrated in the visual feedback. I *think* that the change from square to diamond indicates degree now. I'm not sure how to increase/decrease the degree of a particular node. The help tip should probably indicate how to do that when paused over a path node.
All in all, I couldn't be more impressed with inkscape. Its definitely going to be my staple drawing application. Thanks!
A. Selected control nodes should be more visibly indicated. Their selected status is hard to see.
Agree. I'll see to it soon.
B. There should be a keyboard shortcut to toggle a mode highlighting richer bezier info on the selected path. The user would see, node number 0..N, degree, etc. for each node, near the node. This would be used in enhancement D, among other places.
There's a RFE to add coordinate/angle editing fields (for the selected nodes) to the node controls bar.
C. For multiple nodes sharing the same location, you should be able to keep clicking the spot to cycle through the various nodes, even if they're on different paths. This is probably a general 'drill-down selection' feature request, not just paths.
Alt+click for shapes "selects under". For nodes, it would indeed make sense to do something similar. However it's difficult technically. Please file a RFE, some day I may invent a way to do this.
D. There should be some control over how far along the path between selected nodes the inserted node appears. A toolbar slider going from 0 to 1 would be ideal.
No, simpler than that: just add a node where you click :) There's also an RFE on that. We just need to implement that.
E. The degree of each node needs to be more integrated in the visual feedback. I *think* that the change from square to diamond indicates degree now.
I'm not sure what you mean by degree. The shape of the node indicates its type (corner or smooth).
I'm not sure how to increase/decrease the degree of a particular node. The help tip should probably indicate how to do that when paused over a path node.
Ctrl+click changes the node type, or you can press "c" or "s" for all selected nodes.
Make the circle as a shape.
Convert circle to a path.
Select two of the four control nodes, insert a node.
Inserted node will appear at midpoint on path between selected nodes.
Do not move any nodes yet, you'll damage path's circularity.
Repeat steps 3,4 recursively until you have a node close enough to your
desired cut point at each side of the segment to be removed.
Hmm, why can't you just drag the rightmost controls of the circle as shape, without converting to path? That's exactly what these controls are for. If you don't need the radii, drag the controls from inside the circle. Use Fill&Stroke dialog to remove fill if you don't need it. It's very easy to create an arc of any angle, with or without radii, using these controls. Dragging the controls with Ctrl snaps the angle.
- Selecting the node of the cut segment can be difficult, since they
share the same location as nodes on the preserved path. Use undo immediately if you select the wrong one. You definitely don't want to disturb nodes relating to the curvature of your circle.
In such cases I usually press an arrow key and see which node moves. If it's the wrong one, I move it back and press Tab or Shift+Tab to move selection to the next/previous one, and then try again. It's quite fast when you get used to it.
- Clean up extra nodes near the endpoints *before moving any*. I've found
that you can often remove some of the intermediate nodes placed halfway between other nodes. Removal of a node will only be practical if there is enough weight available in the remaining nodes to replicate the original curvature. Ride the undo button immediately if you remove a critical node and lose curvature.
Pressing Ctrl+L (simplify) will remove all unnecessary nodes at once with very small, if any, distortion in the shape.
On Sun, 21 Nov 2004 13:30:16 -0500, bulia byak <buliabyak@...155...> wrote:
Make the circle as a shape.
Convert circle to a path.
Select two of the four control nodes, insert a node.
Inserted node will appear at midpoint on path between selected nodes.
Do not move any nodes yet, you'll damage path's circularity.
Repeat steps 3,4 recursively until you have a node close enough to your
desired cut point at each side of the segment to be removed.
Hmm, why can't you just drag the rightmost controls of the circle as shape, without converting to path? That's exactly what these controls are for. If you don't need the radii, drag the controls from inside the circle. Use Fill&Stroke dialog to remove fill if you don't need it. It's very easy to create an arc of any angle, with or without radii, using these controls. Dragging the controls with Ctrl snaps the angle.
And yet another simple way to do this (not necessary for ellipses because they have the controls, but useful for other paths): just draw your shape, then draw a separate cut-out path which intersects the first shape in the points you want to cut, select both and do Path > Cut Path, then remove the portion of the shape that you have cut out.
participants (3)
-
bulia byak -
Claus Cyrny -
Jeff Kowalczyk