Punch! CAD
»
ViaCAD & Shark
»
2D Drafting
»
Bezier splines .. horrible to use .. plus, why do they draw deselected ? (#1911)
Rank: Senior Member
Joined: 2/26/2007(UTC) Posts: 2,156
Was thanked: 1 time(s) in 1 post(s)
Bezier splines .. horrible to look at, horrible to use .. they draw with tails assumed already to be a given length, which is usually too long for any kind of a smooth result. Meanwhile the drafting assistant totally spits in your souffle whilst you're drawing any kind of splines .. the DA sorely needs a hover/pause-to-register micro-delay mechanism Go try Illustrator - where every silky smooth bezier's point needs to be given a (dragged) tangent length too - souffle intact - now, isn't that 1000 times better and 1000 times prettier ? PLUS, WHY ON EARTH DO OUR BEZIER SPLINES DRAW DESELECTED - unlike every other spline-type ?? I'd like to see semi-abstracted 'super-splines' in Shark (kinda like in Alias StudioTools) - where you draw thick, beautifully Anti-aliased splines defining both tangent direction and length as you go .. like Illustrator, Pages or SolidWorks .. but additionally you get a separate "Bias" control for tuning the character and quality of the curve (a graphic equalizer for splines if you like). You get to specify "hard points" where a point must remain "matched" to another feature or spline in position or tangency. I want a symmetric spline tool .. it's not too much to ask - most everything has symmetry ! I want to be able to click a spline point and tell it "tangent horizontal", "tangent vertical" or "match to" (where the point will 'stick' in position or tangency to a point on a cross spline or to another object - so I can do effective patch network surfacing !) (.. And bring on better master-slave surface matching) Shitty splines mean shitty surfaces mean shitty solids ! We need the best splines out there - to get the best results ! Any doubt - look at how you draw splines in Illustrator, Alias ST, Pages, SolidWorks .. now try ours. And let's get a first class anti-alias solution in there - so our splines look as good as everyone elses !
Rank: Senior Member
Joined: 2/18/2007(UTC)
Posts: 1,252
Location: Paris & Frankfurt
Thanks: 217 times Was thanked: 164 time(s) in 101 post(s)
Originally Posted by: jol Bezier splines .. horrible to look at, horrible to use .. Shitty splines mean shitty surfaces mean shitty solids ! We need the best splines out there - to get the best results ! Any doubt - look at how you draw splines in Illustrator, Alias ST, Pages, SolidWorks .. now try ours.
I agree 100% with Jol.
In Pages (or Keynote) it's neat & clean, with double tangencies on each point.
JL
Rank: Senior Member
Joined: 6/24/2008(UTC) Posts: 591
Jol, Im surprised....why are you using Beziers and not control point curves ?? The quality of the curves in VC and the matching slope for G1 continuity works very well and thus the quality of the surfaces are also good (Checked in Rhino) you can check in Shark with Zebra:cool: If you use a control point spline you can always maintain tangency at the start using snaps and then with a little knowledge of how nurbs actually works you can get very close at the other end needing just a tweak ;) ( I might add this only works on flat geometry as modify slope doesnt deal with modyfying the curve in 3D, maybe shark does a better job - I'd like to know ? As far as quality of curves on screen, here on the PC with all the settings turned up and using a Quadro card im getting lovely smooth curves on my screen :D.....dont suppose you are using Mac :rolleyes:
Rank: Senior Member
Joined: 2/18/2007(UTC)
Posts: 1,252
Location: Paris & Frankfurt
Thanks: 217 times Was thanked: 164 time(s) in 101 post(s)
Originally Posted by: unique Beziers and not control point curves ??
Beziers could be a much more powerful tool for us.
As Jol said, if it worked just like in Illustrator, or even in iWorks...
JL
Rank: Senior Member
Joined: 6/24/2008(UTC) Posts: 591
Originally Posted by: jlm Beziers could be a much more powerful tool for us. As Jol said, if it worked just like in Illustrator, or even in iWorks... JL
Hi jlm
Maybe...but im not sure how, can you explain why please :confused:
You can always sketch the control point or interp curve and then convert it back to a bezier, but I do see the point myself. I do not use illustrator myself but I would like to see some geometry from the program and compare in VC..
Greets,
Rank: Senior Member
Joined: 2/26/2007(UTC) Posts: 2,156
Was thanked: 1 time(s) in 1 post(s)
Clearly you don't use Illustrator Paul. If you did, you'd understand. Delicate manipulation of splines may be a kind of design you're not into .. typically where there's a styling element I am arguing .. if we include a Bezier tool, let's make it work really well You are arguing .. you don't need Bezier Splines So let's agree .. Dump Beziers - or make them worth using !
Rank: Senior Member
Joined: 2/26/2007(UTC) Posts: 2,156
Was thanked: 1 time(s) in 1 post(s)
>>As far as quality of curves on screen, here on the PC with all the settings turned up and using a Quadro card im getting lovely smooth curves on my screen .....dont suppose you are using Mac Tim has turned off Anti Aliasing on the Mac - It's been off for a year or more due to a nasty crashing problem. I fully expect the team to have a solution to that REAL SOON ! As for your hotrod PC .. I hope you enjoy it : )
Rank: Senior Member
Joined: 6/24/2008(UTC) Posts: 591
Originally Posted by: jol Clearly you don't use Illustrator Paul. If you did, you'd understand. Delicate manipulation of splines may be a kind of design you're not into .. typically where there's a styling element I am arguing .. if we include a Bezier tool, let's make it work really well You are arguing .. you don't need Bezier Splines So let's agree .. Dump Beziers - or make them worth using !
With respect, I use splines/curves for manufacturing on CNC's beit a surface, solid or wireframe, so yes I do need delicate & accurate curve representation.
Illustrator is a professional design package, not really used as Cad although im sure there are plugins now.... I wasn't saying you dont need beziers I was just curious why you are using them. To my knowledge Beziers (and the math behind them) are really only used these days in the motor industries.....are you in this industry ?
Maybe someone else can justify the benefit of keeping the Bezier tool but I would vote to dump Beziers and make space for tools like Extend etc..
Quote: As for your hotrod PC .. I hope you enjoy it : )
You Bet!:D:D
Rank: Senior Member
Joined: 2/26/2007(UTC) Posts: 2,156
Was thanked: 1 time(s) in 1 post(s)
>> To my knowledge Beziers (and the math behind them) are really only used these days in the motor industries.....are you in this industry ? As far as I know that's not the case. Illustrator uses Beziers by default (and you can literally get any shape you want), as does Alias (which uses abstracted beziers) and lots of other apps Ilustrator's beziers are interesting as you can break tangency within a spline (.. but you gotto watch that when coming into general CAD) With Interpolates, you can't always get the shape you want ! Tim would know better but .. I assume more control is the reason people use beziers .. as you can control the tangent length as well as the tangent direction on the endpoints. What's more, each point has a tangent direction / length control, which is not true of Interpolate splines Interpolate splines force a situation where you must sometimes place multiple points together to get around a corner .. and the plot of this is always ugly Control point splines seem to give you a smoother result, but you cant match spline crossover points - so you're out of luck with network patching Yes, I worked at Opel Design in Frankfurt, then for Style Porsche in Weisach .. then later in yacht design in NZ If anyone finds a really good article about splines, can they please post it
Rank: Senior Member
Joined: 6/18/2008(UTC) Posts: 978
Was thanked: 1 time(s) in 1 post(s)
Hi, The splines in VC/shark can certainly be a pain, especially when attempting to create a symmetrical closed 3d spline. I have been meaning (for a while) to post an example with the question of how to correctly create such a shape in VC/shark. I will put a post together now for some feedback. - Steve
Rank: Senior Member
Joined: 6/24/2008(UTC) Posts: 591
Originally Posted by: jol With Interpolates, you can't always get the shape you want !
I must admit I tend to use Rhino for building degree 3 curves but from what I see the tools in VC are reasonable. Probably, the reason you say this is because the curve is not drawn dynamically per point and so unless you are familiar with nurbs (particulalrly building control point curve) you will not end up with what you expect ;)
A good few people now have asked for the to be dynamic to help the designer build high quality curves right first time.
Quote: Interpolate splines force a situation where you must sometimes place multiple points together to get around a corner .. and the plot of this is always ugly
I didnt think the purpose of a smooth curves was to around corners...use lines for this...;)
Quote: Control point splines seem to give you a smoother result, but you cant match spline crossover points - so you're out of luck with network patching
Please give me an example of what you mean here.
Quote: Yes, I worked at Opel Design in Frankfurt, then for Style Porsche in Weisach .. then later in yacht design in NZ If anyone finds a really good article about splines, can they please post it
So none of us are rank amatuers then....
Rank: Senior Member
Joined: 2/23/2007(UTC)
Posts: 484
Thanks: 28 times Was thanked: 50 time(s) in 36 post(s)
Originally Posted by: jol If anyone finds a really good article about splines, can they please post it
[URL="http://en.wikipedia.org/wiki/B%C3%A9zier_curve"]B©ziers[/URL]
[URL="http://en.wikipedia.org/wiki/Nurbs"]NURBS[/URL]
in [URL="http://en.wikipedia.org/wiki/3D_modeling#Modeling_processes"]3D Modeling[/URL]
Norbert
Rank: Senior Member
Joined: 2/26/2007(UTC) Posts: 2,156
Was thanked: 1 time(s) in 1 post(s)
Thanks Norbert - but it's really hard to read this stuff. I need a simpler explanation. Perhaps Tim could explain the pros / cons of our spline toolkit when he gets time >> Please give me an example of what you mean here. wink I'm sure if you're interested in doing this, you'll work it out, wink wink
Rank: Senior Member
Joined: 6/24/2008(UTC) Posts: 591
Originally Posted by: jol >> Please give me an example of what you mean here. wink I'm sure if you're interested in doing this, you'll work it out, wink wink
Errrm no......I would rather you show your own example, how can any user or the development team help otherwise :rolleyes:
Rank: Senior Member
Joined: 2/26/2007(UTC) Posts: 2,156
Was thanked: 1 time(s) in 1 post(s)
Tim is aware o the issue. I suspect he doesn't want to get into constraints in 3D If you'd tried to edit splines in a network surface with multiple cross-curves - you'd understand the advantage of being able to match points on an 'm' curve to points on an 'n' curve wink shrug
Rank: Senior Member
Joined: 2/26/2007(UTC) Posts: 2,156
Was thanked: 1 time(s) in 1 post(s)
I have a couple of other problems come up today with splines .. I'm yet to pinpoint why they happen .. has anyone had either of these ? 1 - Interpolate Splines lose (entirely) the tangency set on their endpoints .. happens again and again - but I can't see under what conditions this happens ie : I'll keep coming back to splines and having to reset their end tangency. Possibly it's after a translation .. but I can't reliably repeat - driving me nuts tho' 2 - On nudge adjusting a point on a spline (not near the origin) .. view rotate centre will suddenly reset to another location entirely - causing my object to spin off into space when I next use the Viewball (Porcupines were ON when this happened - but again, I cannot repeat) Thanks if you can help pinpoint either of these
Rank: Senior Member
Joined: 6/18/2008(UTC) Posts: 978
Was thanked: 1 time(s) in 1 post(s)
Hi jol,
Originally Posted by: jol .. has anyone had either of these ?
Yes,
1 On a closed Interpolated spline, when the spline is segmented then both ends of the spline lose tangency. (I was going to make a post about this, but have not had time to search the forums for similar problems, and I wanted to check to see if this is happening at other times)
2 While control point editing I do lose center of rotation of the view, I usually have to de-select all and reset the view with zoom all.
- Steve
Rank: Senior Member
Joined: 11/4/2007(UTC) Posts: 515
Was thanked: 1 time(s) in 1 post(s)
Originally Posted by: jol >> Ilustrator's beziers are interesting as you can break tangency within a spline (.. but you gotto watch that when coming into general CAD) With Interpolates, you can't always get the shape you want ! Tim would know better but .. I assume more control is the reason people use beziers .. as you can control the tangent length as well as the tangent direction on the endpoints. What's more, each point has a tangent direction / length control, which is not true of Interpolate splines Interpolate splines force a situation where you must sometimes place multiple points together to get around a corner .. and the plot of this is always ugly Control point splines seem to give you a smoother result, but you cant match spline crossover points - so you're out of luck with network patching _______________________________________________________ If anyone finds a really good article about splines, can they please post it
Paul Bourke is a mathematician who's done a lot of work on curves, splines, surfaces and how they're handled in CAD, like this page.
http://ozviz.wasp.uwa.edu.au/~p...ellaneous/interpolation/ This also touches on continuity across control points in splines, and gives some idea of the difficulty in maintaining continuity when editing across an interpolated point or curve. Beziers don't have it, but can be subdivided as explained here:
http://www.antigrain.com/resear...aptive_bezier/index.html giving chained Beziers, which do keep the relationships at their segment endpoints. They maintain interpolation, but aren't inherently smooth.
Rank: Senior Member
Joined: 6/24/2008(UTC) Posts: 591
Originally Posted by: Steve.M 1 On a closed Interpolated spline, when the spline is segmented then both ends of the spline lose tangency. (I was going to make a post about this, but have not had time to search the forums for similar problems, and I wanted to check to see if this is happening at other times)
Hmmmm yeah never noticed that - excellent find coz that could cause some real dissapointment further down the line :rolleyes:
Punch! CAD
»
ViaCAD & Shark
»
2D Drafting
»
Bezier splines .. horrible to use .. plus, why do they draw deselected ? (#1911)
Forum Jump
Punch! CAD
ViaCAD & Shark
- News and Announcements
- General
- 2D Drafting
- Surface Modeling
- Solid Modeling
- Subdivision Modeling
- Rendering & Display
- Import/Export
- Tips and Tutorials
- Suggestions
- Gallery
- PowerPack
- Punch Lounge
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.