Hello,

I convinced my brother in law to buy MoI because he needed a solar panel design, so I've been working on the program for a little bit. I really love how easy it is to learn and use MoI. I have three questions, don't know if they are correctly termed or make sense at all...but here they go...

1. Is there a way to create a snap point on a curve at the intersection (and/or projected intersection?) with another a curve or line?
The background for this, with "edit/show points" on, I can pick an arbitrary point on a curve and snap that to other places or snap points, but i cannot pick the exact point of an intersection or projected intersection using construction lines or any other help geometry. any help would be appreciated.

2. Another similar question which I think may have been asked, but i cannot find the post anymore: is there a way to add/create/show/manipulate edit points that reside on the curve which can be used to drive changes to the curve and snap to points where the curve must pass through?

3. Is there a concept of isoparms built into MoI? If so, is possible to use that as construction aid?

This is my first post.

Many thanks,

Luis

Hi Luis, it sounds like you are looking for a way to edit a curve by moving points that the curve passes through?

There is not really any edit tool for that in MoI currently, if you have some situation where you want to force the curve to pass through some same number of points all the time you will probably need to delete the curve and then draw a new one with Draw curve > Freeform > Through points.

Like you saw, you can manipulate a single point on the curve to force it through another area by dragging directly on the curve when control points are turned on, but that may not help you if you want to maintain a whole sequence of constrain points instead of just one. That mechanism is kind of more intended to be a general curve shaping helper mechanism.


Yeah, if you are drawing new objects, those kinds of snap points will show up on other existing curves automatically, unless you have disabled Object Snap, or disabled Intersection snap specifically, or turned off the option under Options dialog > Snaps > Object snap options > "Use apparent intersections".

But what you may be running into is when you are dragging an object's control points to edit it, it will not snap on to various things that involve itself. That's to avoid a kind of over-snapping problem that can otherwise easily happen. If a curve snapped on to its own self when you were dragging points, it tends to kind of lock things up with snaps and prevent freedom of movement of the points which is bad when you are focused more on trying to adjust the general look and shape of the curve when moving the points around.

So if it is that issue that you're running into - (no self snapping when dragging), you may need to do something like draw an individual Point object (Under Draw curve > More) and then use it as a snap target later.

Let me know if that self-snapping issue was not what you were seeing, if not then if you could possibly post a sample file that would help.

Also, one other note, that apparent intersection stuff will only apply when you are in one of the ortho viewports, not while you are working in the 3D viewport.



No, there's nothing set up for this currently. In the future I want to try to set up something for this by a construction history mechanism, that would allow you to edit the points that you originally picked for a "Curve Through Points".

But if you mean something like the "Edit point" mechanism in Rhino, there are actually a lot of problems with that mechanism so I'm not really planning on doing that exact kind of a thing and also getting those same problems as well...

Check out this other recent post for some illustration and explanation on this:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3364.1



No, there's nothing set up in MoI currently for isoparms.

In Rhino for example the isoparm display has a tendency to obscure interesting details in the surface display, things like little ripples and bumps are often right at an isoparm and having a whole bunch of isoparms additionally displayed tends to get in the way from being able to see more of the actual surface itself.

So it was a focus in MoI to make a cleaner display and not one so choked up with isocurves - those are actually a remnant from the past in Rhino that is inherited from its original wireframe display mode.

I am planning on making a command for extracting an isoparm from a surface though so you would have it as a regular curve to use for whatever you want.

Is there something specific that you would want to get from isoparms ?

- Michael

1. Here is my attempt at explaining it further...Let me know if its not clear...
(see image below)

2. That would be great!!!

3. Curves from isoparms would be even better!!! :) sometimes when looking at wireframes, i kind see the value of
attaching things and/or snapping to isoparms, even reconstructing parts of the surface using some of them or creating
new surfaces through re-wiring....no particular example right now though, but i might come back to you later with it. :)

BTW, Thanks for responding so quickly. I really enjoy working with MoI. Kudos to you for putting it all together.

Best,

Luis



I've also attached the file for anyone to see and experiment.

Hi Luis, just a quick comment on one part:


Yeah using it for reconstruction or constructing other kinds of objects like some tubes or something could be useful.

But I'm not sure if snapping on to isoparms would really give you very much - in MoI version 2 you can just snap to any point you want on a surface, with the new "on srf" object snap.

Here's an example:




Snapping on to only a few isoparms would kind of be a more restricted number of spots on the surface than you can do with just the "on srf" one...

- Michael

Hi luis, thanks for posting the example file, that helps a lot to clarify!

From what I understand of what you are looking for, you could possibly use Scale 1D instead of control point editing to get the right result.

So for example select the orange curve, and then run the Transform > Scale > Scale 1D command.

For the origin of the scale pick this point here (where the mouse cursor is at):




For the direction and first reference point for the scale, pick the intersection point that is on the orange curve, here:




Now for the final stage of Scale1D you have the option to either enter a scale factor like 2.0 to double the size, or you can pick another reference point which will calculate the scale factor for you to exactly scale from the first reference point to the second one.

So for your case here you would pick the ending point you want here:



And then that stretches that curve by exactly the amount needed to relocate from the first intersection to the second intersection:




So if you want to do a kind of a stretching from one particular point exactly to match another one, Scale1D can be useful for that instead of doing any point manipulation stuff.

- Michael

Hi Luis, here is an example that's a bit less busy that shows Scale1D in use for this kind of thing:



There you can see how the curve responds during the Scale1D steps - once you have picked the first reference distance to be locked on to the particular spot, then the last reference point will let you track that point to the new spot.

Was that the kind of thing that you want to do?

One other note - the curves in your file were just slightly non-symmetrical, like the orange curve was slightly not in a vertical plane. So I tightened them up just a bit which gives cleaner kinds of snaps. If you see things like a perpendicular snap is slightly not in the same spot as an intersection where you would expect for them to be the same, it probably means your curve is slightly not symmetrical or planar.

- Michael

Michael,

You're right. i just think the even spacing of isoparms make them useful for additional geometry to be put in place. Being able to extract isoparms as curves would be a great addition though...

On the same note, I have another question since i'm really just learning about surfacing, if you can extract the isoparms as brand new curves and then network them, would you end up with the same surface or would there be a slight difference? I guess i'm asking because sometimes i prefer to see the wire frame and sometimes that affects my modeling approach. I simply don't know enough to understand the subtleties. :)

Any videos or links would be very helpful

Thanks again for the quick response.

--Luis

Hi Michael,

Your solution works great for this example. However, I guess what I was going for is to be able to pick the intersection point of the curve and move it to other snap points on the scene.

With "edit/show points" on, I can do this by clicking anywhere on the curve and picking a point arbitrarily then dragging this "temporary" point and snapping to other things as I would normally do. I would like to do the same, but by being able to pick the intersection as the starting point. Its just I can never quite lock in the "true" intersection even while zoomed in because no pick point or crosshair at that intersection shows up on the screen that I could grab on. This would guarantee the curve is snapped to and passes through the next snap point I choose to place it in. Other tools can do it (e.g. pick the intersection), so I figured why not this one. :)

I dont mind if the nearby control points get slightly modified, what i've noticed is that while dragging the curve with "edit/show points" on, only the nearest 3 control points get affected while the others stay locked in position (at least from what I can tell). What I care about is being able to make slight modifications to the curve around those control points and not have to reconstruct the entire thing all over again, which in come cases I can never get it quite right without doing a lot of other work.

Let me know if this makes sense...

Re: your comment:
quote:

Yeah, this was probably a left over change for when I was trying the "on curve" snap while dragging a point on the orange curve with "edit/show points" on in the top ortho view.

Best,

--Luis