Match curve

[Sketchy]

I've been looking at this feature of Rhino called Match Curve in Amapi Pro. Like, for instance, you create a curve, then mirror it at one of its ends. What if you would like to have a smooth transition at the point where the two curves meet? Amapi Pro 7.5 has this match tangent feature, but it only applies to surfaces, not curves. Did I miss something? Any chance it will be in ver 8?

[ab]

very nice, it will be in "request fonction on the beta-test forum".
Thanks.

[larsen]

When would like two curves to join with a smooth transition I use the fillet tool on the 'break' vertex where the two curves are joined (with the 2d simmetry tool). Don't know if it's useful for you...

[Butch]

It would also be nice if we had a blend two curves option.

[Sketchy]

Such feature (match curve) would probably be not necessary (at least in the current project I'm working on) IF Amapi Pro happens to have a BREAK command, which splits the curve where you pick. Which is probably better because you can control the curvature. Is there? A "break" feature?

I'll post later where this is applicable.

[Butch]

Yes, I also couldnt get where to find usual commands like trim, split, join curves...

[larsen]

You can join 2 curves using the weld tool. You can split a curve into 2 or more pieces using the 'extract curve' tool with the option 'extract part of a line'. You can trim a curve the same way. Hope that helps.

[Butch]

Thanx larsen
Will try!

[larsen]

You're welcome

[Sketchy]

Originally Posted by larsen

You can split a curve into 2 or more pieces using the 'extract curve' tool with the option 'extract part of a line'. You can trim a curve the same way. Hope that helps.

Extract doesn't make any sense. How can you extract something that hasn't been broken yet? Why not add a simple break command which goes something as intuitive as: select curve, invoke break, then point along the curve where you want the break point? Trim doesn't make any sense either. As what it says, trim supposedly trims away excess lines or something.

EDIT:
You're right, EXTRACT does serve the purpose. I was just too dang lazy to explore. Still, adding BREAK would be as normal as adding or deleting points.

[larsen]

Sketchy, I agree with you when you say that a 'Break' tool would be better but I was just suggesting how to trim and split a curve with the current features of Amapi. Nothing more...

[Sketchy]

Take a look at this image taken from the Beetle tutorial by Guilles Brai (http://forums.polyloop.net/tutoriaux...cox-nurbs.html)



I assume the modeler intended for these breaks to have a smooth transition. Thus, instead of creating three separate curves by visual trial and error, you should only create one continuous curve, then be able to break it along any point of it.

Nice tute, BTW.

[gksl4]

I think during a curve construction, pressing SHIFT when you add a new point creates a break point.

[Sketchy]

I see what you mean. However, the break you are talking about doesn't split the curve, it creates a sharp corner instead, which is its main intended function.

Though you can get by without these features (match curve, break) in Amapi's current version and your objective will still be met demonstrated by the car tutorial, it would be much easier if we had them.

I'm sure you've realized by now why these are alll important: Gordon Surface Tool. It's probably one of Amapi's important features, which Rhino and MOI don't currently have (correct me if I'm wrong). It generates complex, irregular surfaces out of a few strategically placed curves.

[jbshorty]

Originally Posted by Sketchy

...Gordon Surface Tool. It's probably one of Amapi's important features, which Rhino and MOI don't currently have (correct me if I'm wrong)...

In Rhino it's called a "Network Surface", been there for a long time...

[Sketchy]

Oh, okay. I stand corrected. I wonder how the workflow goes in Rhino. In Amapi you first pick the longitudinal curves, hit enter, then the latitudinal ones. If you look at the illustration above, all you need to draw are THREE curves, then break or split the third curve in three as shown. Instead of drawing five curves. The way to do this in Amapi, if you want a smooth tangent transition is draw construction lines intersecting the curve first, then used the boolean/cut tool, which, obviously, is a lot of steps to take instead of just drawing one continous curve, then break or split it in any number of curves.

[jbshorty]

in Rhino, you can window select all curves at once, and (assuming they are in logical order) the network tool will auto-sort them for you. If not able to auto-sort, it will then ask you to pick them in proper order... regarding the curve splitting, rhino's split command has a "point" option which lets you pick locations to split the curve. Or in the case of a curve with "kinks" in it (as Guilles' tutorial), you could just "explode" the curve into 3 parts... I'm not really sure what is the benefit to producing a kinked curve (such as bezier curve tools produce). They often cause trouble later when developing surfaces. If you know in advance that you need 3 individual curves, it is probably better to just make 3 seperate curves to begin with. Just my experience in general...

[Sketchy]

I thought the whole point of using NURBS tools instead of poly tools is to be able to control the accuracy. If you, for example, draw three connected curves separately as parts of a network/gordon surface and make them look as if it's one continuous curve, it would be obvious that it will never be mathematically accurate especially in a 3d environment. It's hard enough to draw such curves on a 2d surface, let alone in 3d. (I mean if you're no so concerned about accuracy, then it would be easy.) The obvious solution is provide a way to correct the "kinks" by adding something like the match curve or smooth function, or break.

[jbshorty]

Originally Posted by Sketchy

...If you, for example, draw three connected curves separately as parts of a network/gordon surface and make them look as if it's one continuous curve, it would be obvious that it will never be mathematically accurate...

Not true. if the program is able to draw tangent curves, then the result will be same as if you split one curve into segments. I am guessing Amapi must have some method for drawing tangent curves, but maybe no method for realigning them (based on your request)... My comment earlier about using bezier curves is just to be careful because most programs draw them by stacking control points on top of each other. A stacked curve point can produce a row of stacked surface points. So it's generally better to use Nurbs curves...

Originally Posted by Sketchy

...The obvious solution is provide a way to correct the "kinks" by adding something like the match curve or smooth function, or break...

of course!

[Sketchy]

The line/curve tools in Amapi Pro are almost complete, imho. If they are not, there are lots of workarounds to be able to come up with what you're aiming at. If we talk about enhancing them further, the best way to do it is, I think, add tons of editing features. As in AutoCAD, the workflow should be to sketch your heart away, then enhance details later. Sketch>Edit...Sketch>Edit... Sketch>Edit...Sketch>Edit...Sketch>Edit...

jbshorty, Amapi Pro does have the option of attaching the next curve you create to one of the last curve's ends, but it has not option of making it tangent to it. Why should it? I don't think I have seen such a program that lets you do that.