Hi,

is there a way to visualise "corner points" like say by changing the color or the shape maybe? If not then it could be useful maybe others.

Thanks,
Felix

Hi Felix, there is not currently any way to do that, but I do want to add some different options for marking different features of a curve, like just the start/end of an open curve and similar stuff like that. So this would be another good option to add when I have a place set up in the UI to control such things. I think it will go on some kind of extended object properties dialog.

- Michael

Thanks Michael,

a little bit of patience on my part...

Felix

I also would find it useful to have more control over control points on curves. Such as convert from smooth to corner and allow individual editing of the fly-out handles such as you would be able to do in a vector drawing program.

Hi jtucker,

> I also would find it useful to have more control over control points on curves. Such as convert from smooth to corner

Yup, a method to convert from smooth to corner is on my "todo" list. In the meantime you can just insert a corner point nearby and delete the previous smooth point to get that done.

But I expect to make some controls pop up in the properties panel when you have control points selected that will streamline that.


> and allow individual editing of the fly-out handles such as you would be able to do in a vector drawing program.

Could you maybe describe this part in some more detail? You can already edit individual control points in MoI currently, you just click and drag on any one individual point and you will then be manipulating that one point...

- Michael

Michael,

What is the best way to include some examples? When I interact with my customers I usually use powerpoint slides. Wil that work on this forum?

Hi jtucker,

Do yo mean bézier handles?

I much prefer working with bsplines than bézier, I wish every 2d program would have some!

Marc

Michael,

Here are a couple examples:
Corel.jpg and Corel000.jpg are from MoI which show basic editing of control points for a polyline.

I created the same polyline in Corel Draw as Corel002.jpg. It has the same type control points.

If I select one point and "Convert to Curve" I get Corel004.jpg. You can see that pont and teh previous point in the segment now have "flyout control arms" (there is probably a technical term for those but the name escapes me) that adjust the spline curvature without moving the contol node point.

Corel005.jpg converts the second segmet to a curve. Now control point two has two "flyout control arms" that can be "tangent" (for smooth curve) as in Corel005 or "independent" for sharp corner as in Corel006.jpg. These arms and points can be moved independently, added, removed or converted back to plain control points. Some type of function such as this would be very useful I think.

Those bezier handles shown are basically tan snaps in MoI for a second point on the curve.. To do this with polylines you would have to seperate them, then you could run rebuild to make the line have 4 points instead of 2. Then, drag the inner point around. If you wanted the opposing point to remain untouched, you would rebuld with 5 points, to get a point seperating the 2 inner points. MoI bezier handles.

Hi jtucker,

> What is the best way to include some examples?

Screenshots like you already did above are a great way!

- Michael

Hi jtucker - re: Bezier handles - Beziers are the equivalent of having a bunch of separate 4 point curves in MoI - with a NURBS curve the first inside points control the end tangent of the curve, so for example with a 4-point curve in MoI where you see this type of control points:



That is actually already exactly the same thing as having the Bezier handles that you are talking about, the "handles" would be like this:




The thing that's good about NURBS curves instead of Beziers is that a NURBS curve is actually able to have more than 4 points in it though - the style of Bezier curve editing that you show above actually works by having a bunch of separate little 4-point Bezier curves like this chained together, that's what makes for there to be that sort of big set of "on curve flyout" handles on it. The problem with that type of mechanism is that the pieces only join together with tangent continuity and not any higher degree of smoothness (except when you have the "symmetrical" handle style).

NURBS curves were actually invented largely to solve that exact problem, so that you could have a curve with a longer set of control points in it that had a higher degree of smoothness throughout the curve instead of having a certain kind of break of smoothness in between all those little curve pieces.

So making that exact same kind of system with a whole bunch of "flyout control arms" at different locations along the curve is not technically good since there is a degradation of the actual smoothness quality of the curve that comes along with that.

But the way NURBS curves work you do have the equivalent of those arms at the start and end of the curves with the first and second points and the last 2 points forming the equivalent of one of those arms like I show above. It's basically a desirable feature though that you are able to not have those kinds of arms in interior smooth areas though since that allows for a higher degree of smoothness of the interior parts of the curve.

So it's sort of a "feature" to actually not have those kinds of handles inside of smooth areas - each one of those kinds of handles that you show there unless at symmetrical style are actually a break in curvature continuity of the curve there, there's basically a lack of higher order smoothness at those juncture points and that kind of curvature break is much more noticeable on 3D surfaces that are generated from such curves than ones used for 2D only... So that's sort of why that sort of older style Bezier handle mechanism is not a great fit for 3D type work.

So anyway, that's why it's not too likely that MoI would get that exact style of editing, it actually has technical quality problems associated with it. After you use the NURBS method for a while you will probably get more used to it and see quite a lot of benefits though - you'll start to notice the curve quality is greater and start to be able to notice a sort of lumpy-ness to the Bezier style curves that happens right at each handle location (due to lack of curvature continuity). Also the way NURBS curves behave tends to be more natural when placing control points because each point that you place tends to more naturally shape curve instead of the sort of "yank out a tangent that bulges out previous sections of the curve" style behavior of the older-style Bezier drawing tools.

- Michael

Hi jucker, also those steps that you show of initially drawing a polyline and then switching it to be a smooth curve would be an unusual way to approach it in MoI - in MoI if you know that you want to have a smooth curve just draw it that way with a control point curve right from the start...

If you have a straight section that you want to switch to being bulgy, then you can use Edit > Add pt, to add some control points to that segment, it will then be bendy in the same way that you show there:

Starting with this polyline:



You can add 2 control points to this section here:



Then when you move those you will get the same kind of thing that you were showing:



If you want to make it a smooth piece connecting to the next section, add some more points to the next section too, then delete the corner point at the juncture between the segments:



That will fuse together those 2 segments into one long smooth segment and you will then have smooth curve editing behavior on that longer sequence of 6 control points:




But it's not really so typical to convert things back and forth in this way - usually if you know you want a curvy piece you should just draw it directly by using Draw curve > Control points, then there is no conversion needed. Also it's pretty unusual to need to go the reverse way and try to form something made of straight lines from an existing curve, it just does not come up all that often and when it does the simple way to do it is to just draw in some new lines how you want them and delete the curvy piece.

- Michael