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# Curved polyline enhancements

## Question

How about some proper B-spline curve ability in the Polyline tool? eg placing the curve by control points, and being able to edit by control points also, just for a start.

## Recommended Posts

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Uh, what more than what the polyline tool does now do you need? The mode bar has four options for each vertex as you are drawing the poly. Corner, Bezier, Cubic Spline and Arc. You can use the U key (in the default workspaces) to switch the vertex point while you are in the process of drawing.

The 2D Reshape tool will let you move and change the vertex points of a polyline. The first mode lets you move vertex points, the second lets you change the type of vertex point. Third and fourth are for adding and deleting vertex points and the last mode is to show/hide the next edge.

Pat

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How about the ability to place an arc with a defined radius between 2 intersecting lines where the intersection point remains the control point, the basis of all manual & digital road design. Most importantly stop the mid point between vertexes from controlling the arc radius that can be inserted. This request started in 1992.

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Pat, the more is just what I said, being able to place and modify a b-spline polyline by its control points, not by points on the line as it is with the cubic spline mode. Being able to define the "order" of the b-spline eg 3rd, 4th, 5th order etc.

Bruce I like your idea too.

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Aren't the Bezier control points b-splines? They certainly don't sit on the line. Do you just want more control? What benefits to higher order splines give you?

As you have probably guesses, I am not a math wiz, and I have never worked in a program that does b-splines. Or at least not one that calls them that.

Pat

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No the Bezier curve is a different sort of curve altogether. I'm not so great on my maths any more either, so I can't tell you all the technical ins and outs of different curve types.

To put it simply, I think placing and editing by control points gives you a lot more control over the outcome of the line, and usually can end up defining the curve with less points than you would by using the Cubic Spline option.

The different order b-splines just determines how close the curve follows the control polygon, and how many points as a minimum it needs to define it. To illustrate, I have attached a screen capture of some different order b-splines. The dashed lines indicate the control polygon and are normally turned off, while the dots at the vertices of that polygon are the control points and are where I clicked in the drawing to place the curve.

HTH

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The Bezier and Cubic Spline curves would be easier to modify and control if they had handles like Adobe Illustrator has. If you look at the Video Tutorial here you will see what I mean. http://www.adobe.com/designcenter/tutorials/aft7am_bezier/#

This image shows the type of handles I am referring to.

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No the Bezier curve is a different sort of curve altogether. I'm not so great on my maths any more either, so I can't tell you all the technical ins and outs of different curve types.

Hi Richard,

???The Bezier curve segment used in VW is a real Bezier curve, but it is a subset of the generic Bezier curves you are probably used to editing in programs like Freehand (loved that program) or Illustrator. The generic Bezier curve segment has two end points (on the curve) and two control points (off the curve). VW uses a simplified construct that combines the two control points into one. This configuration is also used heavily in TrueType font outlines (and others).

???In the VW Bezier curve segment the control points you are used to seeing are situated 2/3 of the way between the Corner points and the single "Bezier" control point and are not individually selectable. The reason for this model is it greatly simplifies the math for drawing the curves.

???Without getting into too much minutiae, the general equations for Bezier curve segments are cubic polynomials (powers of 3). The version of Bezier curves used in VW simplifies the equations to quadratic polynomials (powers of 2), which reduces the formulae by two multiplication operations for each point on the curve (one for X and one for Y) and is a HUGE time saver when thousands of curves need to be redrawn with possibly a hundred points in each segment. It's most likely all documented nicely in a text book somewhere, but I stumbled on this the slow way. Needless to say, I found the math quite interesting.

???Though I would also like to see Bezier curves fully implemented in VW, I have not run into a situation where the VW version doesn't work. The only major thing you can't do with the VW Bezier that you can with the more generic variety is create a loop with one curve segment. Since everything I have ever needed Bezier curves for was drawing outlines of physical objects, this has never been a serious problem, but if you're used to editing the general kind I can see where you might get frustrated.

HTH,

Raymond

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Hi Raymond,

Thanks for your fill-in detail on Bezier curves!! I am actually not used to creating and editing Bezier curves at all, I usually get extremely frustrated with them in programs like Freehand and Illustrator. I am much more used to creating and editing B-spline curves with control points in Microstation which is incredibly quick and easy to achieve a good looking curve. I am very glad to see that at least one can create a proper loop with the Cubic Spline mode.

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One of the problems with VWs Bezier and Spline curves is that they aren't curves. They are in fact closed objects with one edge 'hidden' (see images below). The additional 'Centre' handle that you see is the centre of the 'hidden edge'. If you make this connecting edge visible and then change the smoothing it will act as a closed curve. With the connecting edge invisible the smoothing change only happens on the visible curve parts.

The problem is there is nothing to identify which of the two 'Centre Handles' is the curve handle when you are using the 2D Reshape tool. The user can easily choose the incorrect 'Centre Handle' and not reshape as they actually wanted to. To prevent this erroneous reshaping the 'Centre Handle' to the hidden edge should not be visible when you are in reshape mode.

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Yes I agree - it would be nice to have a curve object that is distinct from a polyline

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That's it! That's what's missing!

Now I see why I've always had such a hard time using that tool.

The irony is that the simple little page layout program from Apple, called "Pages" has a shape tool that has handles like that.

It costs \$79 and comes with two other programs. Why does VW lack such a simple 2D drawing tool enhancement?

The Bezier and Cubic Spline curves would be easier to modify and control if they had handles like Adobe Illustrator has. If you look at the Video Tutorial here you will see what I mean. http://www.adobe.com/designcenter/tutorials/aft7am_bezier/#

This image shows the type of handles I am referring to.

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New to VW... Those of you with experience here, what do you think the odds are that they will improve their curve drawing tools in the near future? For me this is a huge drawback. Seems like this is a consistent complaint that hasn't been addressed (judging from the previous posts). I'm sure I can draw anything (already designed) with the current curve tools, but I want to be able to interactively make decisions with my drawing tools. And this curve tool is just too "squishy" and/or too laborious. Would be great if someone developed a plug-in that was based on the Adobe bezier tool... AutoCAD doesn't do a bad job with the Polyline Splines, even though I have to redraw them if I go to 3d. I guess that is a trade-off.

Mike, the problem for me seems to be that the control point moves, and you don't have both handles on the bezier. I thought before reading this thread that I was just doing something wrong, but now I think the tool is just designed to work that way. I assume it has to do with a choice by the VW folks vis-a-vis computational overhead like someone said before. But, for me, it makes the program almost unusable... Oh well. I'm going to finish this test set of drawings and see if I get better at it.

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http://www.math.ubc.ca/~cass/gfx/bezier.html

Bezier curves

Bezier curves are used in computer graphics to produce curves which appear reasonably smooth at all scales (as opposed to polygonal lines, which will not scale nicely).

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I read that post. Is there a way I can use that Java code to make a tool that uses Illustrator-like bezier curves? I do mostly site work, roads, etc, and I get files from AutoCAD-using consultants with curves. The curves have hundreds of control points on curves that could have 10-15 points. The curves are basically non-editable. I have purchased the plug-ins from Vectorbits, maybe that will help.

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Now this is what i do Love about VW and the Forum Users.

i get on OK with the 2D Reshape tool, and with Mr. Mullin's "Reshaper" improving what's missing in VW toolset, i don't find the 2D Reshape that lacking.

Nevertheless, the Forum Paramedics Pat, Mike and Raymond always manage to explain bits that never made any sense before.

Thanx Guys.

i should point out though, that i too like Illustrators method of dealing with editing Beziers and VW can often be a little TOO clunky to get exactly what is required of it, so Raymond, maybe you could do something for WJustice and me in the shape of a "Reshape" enhancer plug . . . . . .

Oooops! maybe that's one too many requests, Sorry Ray!

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Check out Raven ... play the vimeo tutorial :

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Yeah, looks like that'll do it, Edward.

Now, if we could convince them to make a plug for VW . . . . .

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