Does anyone really understand the Bezier Tool?

[Scott Shepherd]

I'm been piddling around in Corel for 10 months or so and prior to that I have drawn a lot of things in various graphics programs. One tool has scrambled my brain more than any other over the years, and still continues to do so today and that is the darned Bezier Tool.

Does anyone else fight this thing? I've tried to be nice to it, I've tried to be friendly with it, but it just wants to be a bear. I honestly can't understand when, where, and how it works. Oh, I use it, and I use it a good bit, but there's a big difference in getting by or making it work to being good at it.

Let's take something simple like the Nike swoosh symbol as an example. I start at the top pointed part of the graphic, come down to the bottom arc, get that entire bottom side looking good and then the trouble starts. It appears to go into some "chain" mode where as what you do next is highly impacted by what you JUST did. So the fact that I just drew a big swooping arc seems to prevent me from drawing a straight line or even a small arc next. How I do you draw with the thing so that every next step isn't dependent on what you just did.

Another example, I should, in theory, be able to draw a rectangle with all corners having a radius on them. Wow, what a challenge that is with that tool (I know it's not the right tool for that, but work with me).

I have used it and had the tool seem to allow for just what I am describing. Draw a big arc and then go directly into a dead straight line. I've done it, I just don't know how I did it.

Anyone else fight this tool that seems so powerful, yet so misunderstood?

[Gary Hair]

I don't know anything about one segment dependant on the next, I'll leave that to someone else. However, you can change what a segment is by right-clicking on it. You can change a curve to a line and vice versa. That may solve most of your problem. As for using it to draw a rectangle with curved corners - don't... use the right tool for that and you end your problem, why make things harder on yourself?

Gary

[Scott Shepherd]

Gary, I wouldn't consider using it to draw a rectangle to with 4 round corners, but for the ease of describing the situation, it's a lot easy to verbally describe that than it is to describe an odd shape with radii in various places. The concept I'm trying to get across is transitioning between a radius and a straight line, or a large radius with a small radius after it, then a straight line.

[Scott Shepherd]

Here's an example attached.

[Ed Newbold]

There's a number of ways to do what you want, but I opted for the easier solution - to attach a straight line to the top end of your bezier curve. See attached .cdr file.

Cheers,

[Michael Kowalczyk]

Hey Scott or anyone else that use Corel Draw,
Here is a great addition to have delivered to you FREE each month in your email coreldrawpro dot com (http://coreldrawpro dot com/) . You can download the free Emag in PDF format or read on and see what else fits your business needs. Great articles/tutorials on the never ending ways to use Corel Draw.

Hope this helps someone and did I mention that it's free.

[Scott Shepherd]

Hi Ed, I'm obviously having a more difficult time explaining it than anything else. I'm aware I can take an item drawn with the Bezier tool and then just click on some other tool and use that, connecting it to the end of the original tool.

What I'm talking about is continuously drawing an item using that tool. Maybe a good example of what I am speaking of would be to try and make the letter "S" type shape by using the bezier tool. You can get the large radii, but when you try and put a small radius on the ends of the letters, you get craziness. Does that make sense?

Sorry for not explaining this better to start with.

[Mitchell Andrus]

See attached. Scott, you must have something switched on or off or somthin... I had no problem drawing a straight line in either direction.

[Scott Shepherd]

Here's another example, and no comments about "well, it's much easier to just type the letter S in and be done with it" :D

[Robert Goodwin]

But used Bezier curves a bit in college. Granted it has been awhile. I don't use all of the Math I learned on a day to day basis. We seem to subcontract all of our intense mathematical algorithmic work :(. Anyways, yes as you add points to a bezier, it impacts the entire curve. The more points you add, the less noticeable it is but they do adjust none the less.

[Hilton Lister]

The way to change from a straight node to a curved node is to drag the mouse when clicking.
However, the easiest way to draw with the bezier tool is to put all your nodes in as straight ones when clicking with the pick tool. Then select all of the nodes with the shape tool and convert them to curved ones (property bar) and then you can drag the lines to the shape and position you require. I do 90% of my drawing and tracing this way (especially tracing shapes over scans to position my laser work when engraving odd shaped items)

[Dave West]

Try this. Using the .cdr you posted, with the 'Shape Tool' right click on node #4 and choose Cusp. You'll now see the 2 bezier handles. Grab the one on the bottom (closest one to node 5) and drag it up. Point it at node 5 and its now a straight line.
What you're doing is breaking the tangent which allows you to manipulate the handles independent of each other.

Dave

[Larry Bratton]

Scott:
I didn't read all the other stuff in this post(too lazy) BUT I use the bezier tool all the time. Many times when I need something traced and the trace module doesn't do it for me so that I like it, I just use it to make my own trace.
The main thing to remember is that you need to close the path that you make. Simply add nodes, the bezier tool connects each node as added. Continue until you get back to where you started, sit the last node on top of the first one and click. If you look at this process in object manager, when you finish you will see you have one curve.
Once done, you can use the node editing tool to move the nodes and shape the object you have made.
I also use it to make containers for Power Clipping. When I have a white area in a photo background, I want to laser engrave, for example, I use the bezier tool to make an outline around the subject I want to isolate. Then once the object (container) is created by closing the path, you can then power clip the bitmap into it and only the subject will engrave.

[George Elston]

Scott
The crux of your problem is the CUSP, if I understand you correctly. When I draw something from scratch, like the NIKE symbol. I draw straight lines from point to point. Then select all points, change to curve, select all points change to CUSP. A curve has a smooth function, and one handle affects the other. When it is a cusp each handle is independent.

And the thing about the more points the smoother, is erroneous. A curve should have as few points as possible. If you look at the files I have posted you will notice that there are not many nodes in the objects, for two reasons. One the cut is smoother and two the cutting is faster. The laser driver figures the path to the next point one point at a time. If you notice your laser slowing down in a particular section of a file, look at the number of nodes in that section. A while ago I posted a horse and carriage scene, in the original and simplified version. Compare the run times on the two versions and see what I mean.

Hope this helps

[Bill Cunningham]

Were I find the bezier tool most effective is for converting simple bitmaps into vectors.. When your customer sends you the 75 dpi logo that you just knew you were going to get from them :D 75 dpi is too low a res for trace to do a good job on, but the human eye is wonderful for that.. Just import it and paste in on the screen, then using the bezier click it around the perimeter of the logo, sort of like stitching a line.. The closer you click and create the nodes, the more accurate the the vector line is going to be..Just keep stitching around until your back at the first node. You can then convert the nodes from straight lines to manipulatet them further, just like in the old days when you used a point and click digitizer to get logos into your mechanical engraver.. Once you have 'stiched in' the entire logo, you can delete the bit image, and finish up the vector. Although this can be time consuming, sometimes this is faster than explaining to a customer why a web graphic can't be used..

[Mike Hood]

Bezier curves are REALLY handy when doing aerodynamic forms. When flow and drag are concerns... they can't be beat. They scale perfectly and when laser cutting they are faster and smoother than their counterparts.

Here's a cool place I took my son to explain how to use them. It makes for a good place to learn the aspects of drawing using a Bezier curve.

http://www.cs.unc.edu/~mantler/research/bezier/ (http://www.cs.unc.edu/%7Emantler/research/bezier/)

[Roy Brewer]

Steve,

I believe I understand what you want to do and I have a terrific solution for you if you take the A&E periodical. If you don't, then you should reconsider. They'll send you several issues for free just for requesting.

Jim Sadler had several months of articles explaining the hot keys to create a closed path on the fly switching between line sements, symetrical sements, smooth sements and cusp sements (quite similar, but much better, than aCadd Polylines). Although most DRAW users do what others have posted in this thread (create all line segments, convert to curve segments and finally modify them to the type curve required), Corel powerusers do it the way Jim explains and will do it in a fraction of the time(certainly less than 1/2). The secret is "C", "S" and how you pull away from a node entered, but nothing less than the detailed steps Jim provides in his tutorial would make sense.

Jim, a former university graphics professor, was with Romark for several years and recently went out on his own and has for a few years been writing great articles for A&E. He is very good at illustrating abstract concepts with the "step by step" that many of us prefer.

If you can't get these articles from A&E directly or borrow them from someone around you who does, I'll see if I can get permission to send you a copy of the articles.

If allowed? http://www.a-e-mag.com

[Ed Newbold]

Here's another example, and no comments about "well, it's much easier to just type the letter S in and be done with it" :DAhhh... yes. Now I see what you're referring to. Others have already answered it correctly: It's the "cusp" setting you have to adjust. Do it like this:

1 and 2. lasso all of the nodes in your curved line.
3. right-click on them and select "cusp" from the menu
4. now any node handle you change is independent of any other node handle, and you can do what you wanted to do all along.

Cheers,
Ed

[George Elston]

Yes, the CUSP

Prof. Bezier, of Renault motors, (France) originally worked out the math and mechanics of the curve to design the Renault Daulfien (sp-spell check can't help on this one).

One further tip, change the end nodes of straight lines back to "Line", it's really hard to get the Bezier handles perfectly inside their origin, and why should the software have to figure a curve when it doesn't have to.

[Bill Cunningham]

Yes, the CUSP

Prof. Bezier, of Renault motors, (France) originally worked out the math and mechanics of the curve to design the Renault Daulfien (sp-spell check can't help on this one).

Hey!!! My very first car was a 1957 Renault Daulphine..
It got 50 miles to the quart...of oil...:eek:

[George Elston]

Hey!!! My very first car was a 1957 Renault Daulphine..
It got 50 miles to the quart...of oil...:eek:

Come to think of it my first car was a Renault Daulphine, ran great until I steam cleaned all the gunk off the engine, right down to the huge crack in the block, then I didn't get 50 feet to the quart.