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Can we have a Polyline to in Sketch?
ed_long
Member Posts: 5 PRO
Can we have a Polyline tool in Sketch?
Like in CAD, you do PL and begin a continuous series of polyline segments and you can switch from straight line to arcs on the fly and go until you have a closed polyline if you need to.
I ask because it is how I do a major percent of my work. Even for things that will be extruded to 3D.
For what I do I would do the completed closed polyline shape, then offset that, then I would be at a point where I need to extrude to 3D
Like in CAD, you do PL and begin a continuous series of polyline segments and you can switch from straight line to arcs on the fly and go until you have a closed polyline if you need to.
I ask because it is how I do a major percent of my work. Even for things that will be extruded to 3D.
For what I do I would do the completed closed polyline shape, then offset that, then I would be at a point where I need to extrude to 3D
2
Comments
I have seen different sketchers do this in different ways. Solidworks uses a hotkey or gesture.
The bottom line is that it reduces mouse clicks and wrist movement a little which can help with RSI specifically and user happiness in general.
Low priority compared to things like drawings and external references though
Presently in Onshape from a single command we don’t have such option but we can do a work around like by using shortcut keys(“A” for arc and “L“ for line)
Whenever you want to switch line to arc then press “ A” from keyboard and if you want switch to line from arc then press “L” from keyboard.
1) the Onshape user must resnap to the endpoint after each switch. In Solidworks, the terminal endpoint from the entity just drawn becomes the start endpoint of the next.
2) the Onshape arcs are not tangent arcs as in Solidworks, they are three point arcs, so tangency has to be established separately.
The combined impact on productivity is substantial.
ed_long, I might be mis-interpreting your request.
I do miss the toggle between arc/line that SW did and used it frequently.
One thing that both SW & OS do that's not easy to understand:
-Clicking while in the line command creates an ungrouped continuos set of lines.
-Click and hold down, move the mouse, and let go of the mouse button, makes a single line segment.
A series of tangential arcs, if that's what I'm after, I'll switch to a spline and get 3rd order blending which looks better when extruded.
Tangential Arcs vs. A Spline
Original Post
Creating things other than an extruded block requires curves either an arc or a spline. I prefer a spline due to it's amazing control.
Below are 2 arcs confined by a tangent constraint:
I've added 2 points highlighting the 2 inflection points contained in my double arc geometry. Knowing a little math from grade school, I remember the order of the equation minus 1 equals the number of inflection points. Or, because there are only 2 inflection points, I can fit a 2 noded spline on my double arcs:
I've created a new sketch and tied the spline's end points to my arc combo.
You'll have to excuse my crude math expressions (I'd tried finding some pretty spline equations on the internet and failed to find the form I wanted).
2 Noded Basic Spline Equations
a1 + b1x + c1x^2 + d1x^3=0
a2 + b2y + c2y^2 + d2y^3=0
a3 + b3z + c3z^2 + d3z^3=0
A basic spline is a third order expression and therefore can have 2 inflection points. Since my arcs have 2 inflection points, I knew a could fit a 2 noded spline onto my double arcs.
Splines have handles and when you drag them all the a's, b's, c's & d's begin to change. These are your spline coefficients and are controlled by handles.
I can drag the handles around until my spline matches the double arcs (the arcs are underneath my spline):
But, I can have more control and create many new shapes:
You can do a lot with just a 2 noded spline:
Oh yeah, extrude a surface, absolutely:
One thing to note, and I'm not sure in my mind if this is a bug or not, spline nodes can have a natural state meaning no control has been entered by pulling a spline handle. We use to describe the natural state of a curve as the least distance to get to a node. Not sure if it's true but it looks like it is. In OS you can't appear to remove a node's control and return the curve to it's natural condition. I'm not sure this is a bug and want to wait to see where they take spline control.
One thing that's new in OS is being able to grab the spline itself and tug it. This is new and gives us a tug/pull capability that many have always wanted. Since surfaces are nothing more than a few spline definitions, we should be able to tug/pull surfaces which many have wanted.
The next step, make surface patches behave to tug/pull and you'll have sub-divisional surfaces. I think the hooks for sub-divisional surfacing is in the basic spline definitions and will make implementing them a clean/powerful extension. This is much better than a CAD system without this capability meaning to add this control, you have to track your own splines and try to map them back to the system's splines. All this means is a clunky interface trying to add sub-division to a system that wasn't designed to have them.
I wrote this because I want us all to move beyond 2 tangential arcs and poly-lines.