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Bezier gets bulged when joining to other lines or curves
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Hello, everybody,
I wonder if it's because of my ignorance or if it's really just not working properly. I am using Shark Cad 10 with Power Pack Pro 10 and as soon as I draw a curve of any kind (Bezier, Control Point Spline, Interpolate Spline etc.) and want to connect it with a straight line (which has a common point with the spline) with the command Join Curve my spline is changed and somehow bulges out uncontrolled. I thought it was the tolerance value but it happens even if I set the tolerance to 0.00. The screenshots show what I mean by this. With a CAD tool in this price range it is from my point of view not acceptable that combining these simple lines without changing them is not possible. Other CAD tools and even Adobe Illustrator can do this without problems. Now I hope that I simply make a mistake and someone can help me here. Many thanks in advance!
Sunny greetings
Carsten
Edited by user Thursday, January 16, 2020 12:52:39 PM(UTC)
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Yeah this happens. I reported it years ago, never really sure whether I got an answer. I think if you put a really small rad in the corners before the join it works ok. I'm talking like 0.1mm rad so small it wouldn't matter
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Coincidental endpoints are defined as geometrically continuous, apply a fillet between curves and/or lines and you're applying curvature continuity, and when you're joining a curve to a line in PunchCAD you're applying tangential continuity. The bulge you're complaining about results because joining a spline and a line changes the spline's endpoint tangency to that of the line. You get the same effect using connect curve instead, where you don't have the endpoints coincidental and you let the program set the curvature and tangency in keeping with its internal parameters. You control the bulge through the distance between the endpoints of the curves that you're connecting. Where you've drawn the curve and line with coincidental endpoints but don't require curvature or tangent continuity, there's no particular technical reason to join the figures unless you're using them as a compound profile for surface or solid creation. That sort of discontinuity is commonplace in maritime modelling, vessels often have plate surfaces that have blend surfaces between them, or chine definitions between surfaces with dissimilar curvature. Some programs use Bezier segments or compound Beziers with discontinuous interpolation points called "knuckle" points, others like PunchCAD have the capacity to consider a compound profile where line or curve segments meet at their endpoints as a single figure, but you don't need to join them to use them that way, grouping does it when needed.
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Hi Murray, That's fine but why does it look like a train wreck? If the way to keep it flowing, so to speak, is add rads then why doesn't it just add the smallest rad possible? It adds a horrible wobbly line which is literally no use to anyone? If not knowing the set up of what the background technical stuff does when you click join curve, you would literally think it just joins the curves. I ended up using N polygon after I noticed this ages ago. This is so the end points are joined. Cheers
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Why do you want to connect? Group them and use deep select tool to modify.
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Shark/VC are predicated on being conceptual modellers, so my theory is that the intention is that you rough the tangency by eye and leave it to the program to finesse it. By roughing it, I mean using good old human fuzzy logic and approximating the tangency, not doing something randomly contrary to what might be intended and then complaining that the program can't make that into a silk purse. What are you expecting when you join two figures like that, how should the program do it? You can use fillet or connection to get other outcomes.
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Oh here we go. Join curve, just as it says, join the curve. They're straight lines so as the names suggest they get joined. Whether that's end points connected permanently or whatever. When you've worked around what it does and know through arsing around with it you then learn not to use it like that. Like I say I went on to using n polygon or whatever its called. As this has all ends points connected.
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Connect curve does that when their endpoints are coincidental, it keeps them that way, sounds like that's what the OP wants to me, and I would like to know how that's used nowadays, because it's old-school AutoCAD usage to join polylines/polycurves. I'm not asking the question to exasperate you or acting as an apologist. I use this tool as it is and if the behaviour is changed to suit your perceptions, that might oblige me to change my usage to accommodate your preference. I'm not ideologically opposed to change, but I like to know why I should get on board. Join curve adjusts the tangency of the first curve to match that of the second, and you've used another tool to achieve what you want. Are we just discussing the semantics of "join"?
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Coming from Adobe Illustrator I joined lines in the beginning many years ago and had the same problem. Until somebody told me to stop joining lines. I use the join tool to connect curves that does not touch. Often I trim off parts of the curves before joining to make space for a smooth transition. Lines connect easily at their end points by snapping. If you want to move two connected end points you drag a selection box around them with the direct select tool and use the gripper to move.
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Hi thanks for all your explications! Great to have this discussion here. Ok I understand all of your perspectives. For me there are a little more things to throw into the discussion. First handling of a complex drawing. If i have one object it is much more eas to handle. If you have a complex shape and have to fiddle around with lots of nearly 0 fillets it might lead often to problems loosing elements when moving them around. So i'd like to join them to have only one object. Ok grouping might be a solution but this adds another entity in the concept explorer i have also to handle, name, take care off. Second reason is the BOM. If you need to calculate the area of parts it is simply not possible to do this with unjoined lines or curves. So i he to group them to get this done. Third extruding lines from a group means that i have still lots of lines in the concept explorer, if i do this from a joined curve i have only one. And what i also don't like that the group disappears in the concept hierarchy. Forth - coming from other CAD programs makes it difficult to understand the "why does this tool not work like ...". Ok this might be a weak argument but you don't know how annoying it is to make the same fault over and over again if you have to switch between different tools regulary. I work with different tools all the day and it frustrates me after working with Illustrator, Autocad, Vectorworks, 3DS Max, Cinema 4D and so on to see that Shark Cad does it the other way round. It is a matter of usability and to me of user expirience. I use this tool now since some time but never got warm with it. It has several cool features but also some concepts are wired to me. This leads into a feeling of "never be sure" if everything is really like i suggest them to be. So these are some more ideas to think about - handling - overview - steps to complete to archive a result - continuity of object hierarchy. Thanks to all of you discussing this. Have a sunny day! Carsten
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You can also use the polygon drawing tool in the draw polygon palette. You might also convert drawn geometry to polygon in that palette. convert polygon results in a linked to base geometry polygon.
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I would start to use N polygon. All end points are, dare I say it, 'joined' so no problems there. If you then show control points you'll see the connecting points which can be selected and moved a certain distance with the gripper. I used to do this so dimension it all and then do as explained to achieve whatever size needed. Murray, connect curve does work like that but it doesn't become one complete 'joined' curve. So extruding any number of curves, unless you group them but not sure if that works in Shark 10, means going through and selecting or right clicking and selecting chain. The ends jump together but aren't fixed you can still move the end points afterwards. I know grouping didn't work with a lot of things until recently This is why I was keen for constraints, if like me you produce a tool and then customers decided shapes lengths etc need to change it's a task and a half to start moving stuff, without adding more to the history tree, so trying to edit the original form and shape etc is tricky. If like me you are trained to produce simple easy to follow history trees, all these extras should be avoided as much as possible
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Many of these considerations come down to preference, but yes, keeping things tidy is good practice in almost everythings. Using constraints, creating compound profiles or curves becomes moot, constraining endpoints and dealing with sketches. D-Cubed 2D constraints don't work with compound profiles/objects, so you can't constrain a group and conversely, you can't group a constrained profile, but joining or connection is redundant with coincident constraints on the endpoints - unless you require associative tangency, which you can set with arcs, but not with curves, if my memory's working.
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If you join straight lines you have no longer straight lines, you have then just splines and your extruded object are then to complex. Arcs and lines are much better than splines. Also for Laser cutting are arcs and lines better than splines. Use the splines just when arcs and lines are not good enough!!
Edited by user Tuesday, January 21, 2020 5:57:16 AM(UTC)
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OS: Windows 10 | CPU: AMD Ryzen 7 2700 | RAM: 32 GB | Graphic: AMD Radeon RX Vega 56 | Shark FX 9 Build 1162 | Unit: mm
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