CAD/CAM discussion forum > 3D CAD/CAM > 3d curve manipulation

3d curve manipulation

    
  Subscribe Topic

Rank: 1

Eli

Newbie

posts: 0

Registered: 2004-10-28

Message 1 of 18

 3d curve manipulation
12-05-2006 11:38 . am   |   View his/her posts only
Hello all. I am wondering if it is possible to nudge a 3d curve around. I find it nearly impossible to use the 3d curve functions (control point curve or through point curve) without having distinct predetermined points. This can be a real pain in the neck, especially because I have not found it particularly easy to just drag points around so that a curve is to my liking. More often than not my point ends up being at some impossible place in space and I just either resort to importing the curve from another program, or I come up with a tedious workaround using sketches. I design boats, and as a result I use other specialized software, most notably Multisurf from Aerohydro to develop my hulls and some other parts of the boat. One of the nice thing about Multisurf is that I can "nudge" points around to any point in space, and if I am looking at the boat in profile say, I can move the point anywhere in the x and z directions, but the point will be locked in the Y axis. of I am looking at the boat in section I can move a point in the z and Y directions, but x will be locked etc. This is great for getting exactly the curve that I want. Right now I am dealing with a tricky exhaust installation within VX, and I would love to have this functionality so that I can bend the exhaust hose around until I get everything to fit. Anyone have any ideas here? Any help is greatly appreciated. Loving VX by the way...despite some of the quirks, I have been spending all kinds of time using it.

Rank: 1

Robert

Newbie

posts: 0

Registered: 2011-11-22

Message 2 of 18

12-05-2006 10:06 . pm   |   View his/her posts only
Here's a trick that I like...

create a datum in the area that you'd like to "nudge" (select XZ, YZ or any orientation near the desired location)

once you've created your datum, right click on it and select the VIEW option.

VX will automatically "snap" to the planar view on that datum.

Providing that you don't use F2 or Spaceball to rotate, you can nudge your curve around to your heart's content and it will stay "locked" in the current view plane.

Rank: 7Rank: 7Rank: 7

Paul

Moderator

posts: 342

Registered: 2011-9-17

Message 3 of 18

13-05-2006 06:17 . am   |   View his/her posts only
Hi Frosty,
I have spent a great deal of time in small and large engine rooms. Make sure you do a good job for all those people who will have to work in there!
Presumably you have a good model of all existing components to work around.

Your problem is interesting and got me thinking. I am guessing you want to use straights and bends of fixed radius, easy to draw, easy to define and easy to make.. If you can go totally custom, your choice. After trying lots of complicated section ideas, multiple planes and reference lines and finally a 3D curve, I decided this was easiest.

Two sketches, one each on XZ & XY. On the plan view draw the path required in that view around the obstacles. Use Connected lne segments. When finished, chain fillet with the radius of your bends.
Now do the same in the elevation. (Auto constrain when done and leave dims visible.) Now extrude the XZ sketch into a face. Then project the XY plane sketch oto the face, bidirectional if required, and use Y for projection direction.

Run a Rod over the new curve and shell. good ol VX eh!

Now let's see If I can attach this file..

Rank: 1

ChrisWard2k2

Newbie

posts: 2

Registered: 2011-11-22

Message 4 of 18

13-05-2006 11:08 . pm   |   View his/her posts only
Hi cc

How about a marked-up screenshot showing what you wish to acheive? You wouldn't often be bending a hose along a path described by a spline curve but then, how flexible is the hose in this case? What I would normally do is to define the fixing points first, with a centerline through that structure (perpendicular) representing the minimum straight length of hose allowed/possible -each C/L at each fixing point consists therefore of the minimum straight (at least the area of clamping) plus 2x quadrant length of the min bend radius allowed. You can then join these line ends up with lines from fp to fp and finally use the fillet radius tool to insert the bend radius at each joint. You then have your hose centerline and can use the VX rod command to represent the hose. This is a reliable way to construct because the fixture points can be simply represented by Sketches initially - move any point parametrically and your hose c/l will update accordingly.

Rank: 7Rank: 7Rank: 7

Paul

Moderator

posts: 342

Registered: 2011-9-17

Message 5 of 18

14-05-2006 07:14 . pm   |   View his/her posts only
Hi Frosty,
it was very late when I responded previously hence a wee problem with my method. Considering Chris's comments about starting with fixing points, I revise my approach.

Set up the fixing points you'd like to have as Chris suggests. Then on the XZ sketch, reference those points. Now draw the plan view connecting segment lines as before, through the reference points etc. BUT omit the filleting of the lines.
Extrude the XZ sketch again.
(A quick, but no subsequent control method is: Back in wireframe, draw connecting segments drectly on the new face,( RMB on entity). VX will readily find the corners/vertices on the face so it's straight lines every where.)

Now in the XY plane sketch, reference the edges & vertices of the new face. You can bring in any other elevation location references too. Draw the polyline, reference line to reference line, and constrain & dimension as required.

Project sketch as before, chain fillet, (shift select the segments is the trick) and this time you have straight pipes with radiused bends and parametric control viathe two sketches.

My assumption is a particular style of exhaust which presumably will seek to have as few bends etc, as possible. For other service lines etc. this technique can work. even using the same face to represet and offset from walls, bulkheads etc. Different sized pipe work might require different face off sets etc. One sketch could conaint quite a number of pipe guides etc.

Cheers

Rank: 1

Eli

Newbie

posts: 0

Registered: 2004-10-28

Message 6 of 18

15-05-2006 05:18 . pm   |   View his/her posts only
Thanks for the all the responses. I am using a spaceball actually, so perhaps there is one of my problems as far as not being able to locate a point on a plane. As far as nudging points on curves, I see that it really is not possible as I envision it unfortunatly. Chris, one thing that I find with VX that is frustrating is that I can achieve unpredictable results when manipulating things parametrically. Sometimes everything works according to plan, but often enough I get a whole series of errors that just about ruins my afternoon. Once the model reaches a certain level of complexity, I try to steer clear of modifying anything deep in the history brower.

Rank: 1

ChrisWard2k2

Newbie

posts: 2

Registered: 2011-11-22

Message 7 of 18

16-05-2006 12:16 . am   |   View his/her posts only
Hi cc

You should be pretty safe adjusting parametric Sketch Dimensions. When a number of dimensions need to change, the best way to do this is within the sketch itself, to increment each value via the options form, rather than typing in a new value that is greatly different to the original - big jumps in dimension value can cause knock-on effects to the geom that you do not notice at the time, but you certainly feel the pain later

Nudging points on curves is possible but it is far from the best way to get the right shape - too many engineering conditions to satisfy. So you do need a more methodical route.

Rank: 1

OldForumPost

Newbie

posts: 0

Registered: 2012-1-14

Message 8 of 18

16-05-2006 04:39 . am   |   View his/her posts only
Quote

Originally posted by: ChrisW


Nudging points on curves is possible but it is far from the best way to get the right shape - too many engineering conditions to satisfy. So you do need a more methodical route.


Very true for engineering components, but for doing industrial design/vehicle surfacing, nudging points around to get the right surface is vital. As another VX newbie, this thread is very helpful as I was asking the same questions on my first training course last week.

I've been playing around trying to find the best way of manipulating splines (especially in 3d) - you can do everything you need to, but perhaps not as easily as I expected.

Rank: 1

Kevin

Newbie

posts: 0

Registered: 2004-4-26

Message 9 of 18

16-05-2006 05:10 . am   |   View his/her posts only
Is this Owen from Brighton? I agree about the nudging issue. I personally find the 3D curve manipulation awkward in VX. This was one area others have a more flexible/powerful solution. I particularly like the CATIA/Thinkdesign/IronCAD method....why not have a spy at Product Development this week in the UK to see what I mean :-)

Rank: 1

OldForumPost

Newbie

posts: 0

Registered: 2012-1-14

Message 10 of 18

16-05-2006 09:44 . am   |   View his/her posts only
The very same Kevin (I'm not following you round the CAD forums, honest!). Both Rhino and Cobalt are good at tweaking curves, but I haven't seen the CATIA/Think method.

I was thinking of going to Product Development, but then I saw the up to date floor plan last week while at IDS - there were a LOT of empty stands! Not really worth the three plus hour drive from down here, but I guess you're somewhat closer. Anyway I've spent enough hard earned on software for this year.

Rank: 1

ChrisWard2k2

Newbie

posts: 2

Registered: 2011-11-22

Message 11 of 18

16-05-2006 12:29 . pm   |   View his/her posts only
Hi All

Well, what a small world it is then.........or is it that there is hardly anybody left in the UK?

Could you capture the spline point adjusment method that you like best as a movie Kevin?

Rank: 1

Kevin

Newbie

posts: 0

Registered: 2004-4-26

Message 12 of 18

16-05-2006 01:53 . pm   |   View his/her posts only
See what I can do Chris. Don't happen to have CATIA, ThinkDesign or IronCad here but I've sat over the shoulder of users and it looked very simple using the spacemouse and nudge keys (on keyboard and on screen). I do use Cobalt so I'll get that posted when I get a minute.

Rank: 1

OldForumPost

Newbie

posts: 0

Registered: 2012-1-14

Message 13 of 18

16-05-2006 02:24 . pm   |   View his/her posts only
Quote

Originally posted by: ChrisW
Hi All

Well, what a small world it is then.........or is it that there is hardly anybody left in the UK?



Just to re-inforce how small it is Chris; your phone number tells me your based in Swansea, where I grew up and my parents still live.

Rank: 1

ChrisWard2k2

Newbie

posts: 2

Registered: 2011-11-22

Message 14 of 18

16-05-2006 04:26 . pm   |   View his/her posts only
Your parents must be next door, everybody else has emigrated to Spain

Rank: 7Rank: 7Rank: 7

Paul

Moderator

posts: 342

Registered: 2011-9-17

Message 15 of 18

19-05-2006 02:19 . am   |   View his/her posts only
Frosty, how did you get on with your exhaust pipe problem? Solved? If so, how did you decide to do it?

Cheers

Rank: 1

Eli

Newbie

posts: 0

Registered: 2004-10-28

Message 16 of 18

19-05-2006 02:46 . pm   |   View his/her posts only
Hah...well, the space was an issue, as was finding components that would fit. On top of all of this I have to be sure that there is an acceptable level of backpressure on the engine itself, so at the end of the day I handed off that task to an exhaust supplier. I'll end up modeling whatever he comes up with, but at that point I will have well defined points in space to model my pipe around. Chris, as far as tolerances are concerned, nudging curves would be (and is within Multisurf) a very useful feature for those designing things like whole boats. Many of the things that I end up modeling do not have to be modeled with anywhere near the kind of accuracy that someone designing a cell phone would say. In the case of the exhaust, it would be fantastic to have have a 3D spline defined by however many points you wish (fewer the better), and one could just grab points and nudge them in each direction until the desired shape is found. This is exactly how hulls are designed, and the accuracy can be as great as you want it to be depending on how large you set your nudging distance. When I say nudge I mean that a point is selected, and once it is you press some key, say ctrl, then up, down, left or right. As the point moves, the curve updates accordingly. Perhaps this is not something you think needs to be addded to the feature set, but it would be quite nice!
-Eli

Rank: 1

Vance

Newbie

posts: 0

Registered: 2002-8-28

Message 17 of 18

17-07-2006 11:13 . am   |   View his/her posts only
I see that I am two months late, but here are a couple more hints if you really don't need straight lines or radiuses.

First, when dragging a curve that you want to stay in the current viewplane, make sure that you are not picking "on" another entity. If you pick on a curve or face in the background, the point will snap to the curve or face and will not nudge in the current plane. You can make sure that you are not snapping to other geometry by using the RMB menu and setting the pick type to "Absolute". This works in any orientation even if using the SpaceBall.

Second, if you need more control over how much of the curve is being modified as you nudge, try out the Morph commands on the Freeform toolbar. They work on curves in addition to faces. There you can get a dynamic preview of the curve as you nudge the curve in some single direction. This works great, but sometimes produces more points on the curve than you might like. If that matters, you can always reduce the points using Modify NURBS/Reduce Data.

Rank: 7Rank: 7Rank: 7

Paul

Moderator

posts: 342

Registered: 2011-9-17

Message 18 of 18

18-07-2006 07:43 . pm   |   View his/her posts only
This does not apply to 3D curves but 2D curves. When you need to move the entire curve, using move, can be a bit tricky getting precise control, especially if it is only a small move, even with smart pick off and absolute on. There is a tendency to snap back to the start.
Here is a way of getting total parametric control.

Create point constrained to the origin. Then auto constain the curve to the point. Now you can edit the dimentions for the point and all the curve points tag along. You get pretty patterns on screen too. Off course adding a point is not required. You could constain the end of the curve then auto constrain to that point instead. I am sure you get the idea.

SurfDude, the morph tip is cool. I'll have to experiment with that. Go VX
Cheers,
See also
X