Jump to content

Draw on a sphere


Recommended Posts

Does Vectorworks have a way to draw on a sphere?  Similar to the attached Tegan light fixture image, but not so many crossings? Basic process would be a NURBS curve or band object that sticks to the sphere surface as it is wrapped. More difficult would be simulating a material (twine, tape) that makes humps at the crossings. This is not exactly a random path, nor is it just a bunch of great circles.

 

A real world materials process is wrap a plastic lamp post globe (eg 24"Ø) with a roll of narrow masking tape, then cut the untaped areas.  More wraps mean more cuts, but less material removed.  The goal is balancing tape width to number of wraps (or path length) to remove about half the sphere surface.  Another real world method is to soak  twine or cord in a resin and stick it to a beach ball or ballon that can be deflated and removed after the resin sets.  A vwx model could help determine path length and number of crossings to achieve various percentages of openness. Or, the vwx model could be used to 3d print a mold from which an edition of resin "globes" can be cast.

 

Anyway, trying to devise a modeling method hurts my brain. I'm not asking the forum to provide a model, but maybe just some pointers, opinions, or a notice to Cease and Desist (Cyst and Disease?)

 

Current thinking

•Draw a sphere, Convert to Groups (creates a bunch of 3d polygons). Snap a NURBS curve to the array of polys, then EAP.

Seems this could work, but many problems: Difficult to control the wrap direction as it passes over a horizon. Worse, even with X-RAY, the NURBS prefers to snap to the front surface causing more of a bike helmet than a sphere. The path left the surface in several places. Takes a while to render OGL view changes, lots of wraps might overrun the system.

 

•Zoom way back and apply wraps to a georeferenced earth, then massively rescale?

 

•Some kind of solid intersection of a EAP object created near the surface?

Or???

 

-B

Tegan ORB Labyrinth.png

SphereWrap Top.png

SphereWrap Front.png

Link to comment

Thanks, Alan - But texture is not useful. I'm not trying to represent that light fixture, but rather model a simplified, scalable version of that wrapped sphere concept for short run manufacture. I need actual vector geometry with path lengths, area/volume of elements so I can predict loads for engineering, possibly even options for CNC cutting or 3d printing or casting. I really do want to draw a continuous, wrapping NURBS curve on a sphere. 1st hurdle is that bit about snapping to back side of the sphere, or finding a way to spin the view while I draw. Oooh, maybe the multi views in v2018 will help!

 

-B

Link to comment

What about your tesselated mesh sphere to just provide enough snapable points

on the spheres surface to draw your endles spline ... ah ... NURBS Curve.

 

Rotating view without interrupting your drawing tool is CTRL+MMB for temporary

flyover tool, or a 3DConnexion device.

Link to comment

Yes, thanks, Zoomer. I just worked that out with slight variation.  MMB (middle mouse button) is not a good choice for me. I'm not that adroit.

 

I split the mesh sphere along x axis in top plan and assigned different colors to the halves - Yellow/Blue (it's Swedish!). Set view to Front, then skew it slightly so the front intersections are not occluding the back ones.  Now in wire frame I can zoom in/out with the Loupe (z key) to snap a NURBS curve to the intersections. With some practice, the NURBS more or less stays on the sphere. Color code also helps with reshape if initial placement was wrong.  Then EAP the path, convert a sphere to NURBS surface to shell. Then Intersect solids.  But that usually fails. Maybe the ends of the wrap have to be on the surface, too.  More to explore. 

 

My final object will have more wraps, and polar ice caps that the narrow bands connect to - sort of an elaborate jack-o-lantern. Some files attached. vwx layers show the progression.

SplitSphere.png

Solid Intersection.png

Sphere.vwx

Link to comment

Good idea, Kevin.  Didn't work directly (Solid Intersection Fail), but led to an improvement in process:

 

Make the path & EAP as before, interpose it on a new sphere (not the decomposed poly sphere). Convert the new sphere to NURBS surface (no thickness). Solid Intersection the EAP & NURBS sphere. This creates a fairly continuous band wandering around the former sphere surface - more or less as expected. Some areas are missing from the band, it has no fill and does not accept fill. Fix is to cut it on equator (or maybe anywhere) with Split tool.  The resulting surfaces now have fill (Vextorworks mystery). Compose them, or Solid Addition. Finally shell this new solid.

 

OK now to improve & extend the initial wrap/EAP, concoct a complete Solid Section, model & add the polar details, model connection to a light fixture & catenary suspension system, place that in the site, etc. Always more to do!  I will post  as this evolves.

 

-B

ShelledBands.png

  • Like 2
Link to comment
10 hours ago, Benson Shaw said:

Good idea, Kevin.  Didn't work directly (Solid Intersection Fail), but led to an improvement in process:

 

Make the path & EAP as before, interpose it on a new sphere (not the decomposed poly sphere). Convert the new sphere to NURBS surface (no thickness). Solid Intersection the EAP & NURBS sphere. This creates a fairly continuous band wandering around the former sphere surface - more or less as expected. Some areas are missing from the band, it has no fill and does not accept fill. Fix is to cut it on equator (or maybe anywhere) with Split tool.  The resulting surfaces now have fill (Vextorworks mystery). Compose them, or Solid Addition. Finally shell this new solid.

 

OK now to improve & extend the initial wrap/EAP, concoct a complete Solid Section, model & add the polar details, model connection to a light fixture & catenary suspension system, place that in the site, etc. Always more to do!  I will post  as this evolves.

 

-B

ShelledBands.png

I love the look of this result!!

 

(Something has been improved behind the scenes with the Shell tool. While I've had trouble doing additions and subtractions from Shells recently (likely a bug of some sort) the Shell tool will now shell all sorts of things that used to fail. I just shelled a whole series of organic cutouts (tree and bush profiles) that I curved in Rhino without any problems.)

 

Kevin

Link to comment

Islandmon - My forum inspiration!  We miss you man!

 

I also miss Petri, Jan15, Katie, and a bunch of others.

This place can be inspiring, educational, escapist, fun, exasperating, problem solving heaven, a total time sink, . . . you get the picture.

 

Hats off to all participants past, present and future.

 

Oooh, and I do totally want to squash that thing. It might bounce pretty good, too.

-B

Link to comment

These are really cool, Alan! MANY THANKS for the effort and the reporting.   I'm working through your files to see process and potentials.  The spiral wrap is actually not bad.  Having some organization to the wrap gives a fairly clean look, but still distributes the crossings fairly evenly.

 

-B

Link to comment

As I say, really cool. And the spiraling EAP with small profile is a good look, similar to that Labyrinth shade.  This kind of object may be important in later iterations.  For now, I need the EAP path to stay on or very close to the sphere surface.

 

The Marionette generated EAP seems to select points for the path according to increasing distance from the top, rather than, for example, nearest neighbor plus limit on minimum curvature. Maybe this is due to the Fibonacci Sphere Points node. Result is sharp EAP "corners" and relatively straight connectors, with most of EAP hidden in interior of the sphere. At least I couldn't adjust any of the input values to make it deviate from this spiraling path.  More loci (left side nodes in the Marionette network) induced more turns in the EAP spiral, but not more exposed EAP. I swapped the Integer node for EAP Profile radius with an ANY Eval so I could have fractional radius values  because I switched the drawing to from metric to inches. Accomplished that only after I read in vwx Help that the node wires can only be added/removed in Top/Plan. Basic stuff!

 

I still like drawing the NURBS curve by clicking on the color coded mesh intersections. Ctrl>MMB to spin the view is somewhat doable, but Snap loupe in consistent view is most successful for me so far.

 

-B

EAP inside sphere.png

Edited by Benson Shaw
obsession
Link to comment
  • 2 weeks later...

Horsed around with this some more today.  Took a cue from Alan Woodwell (Thanks!) and copy/rotated a good sample to make a denser object.

 

 I snapped a NURBS curve around my front/back mesh sphere, then EAP, then Solid Intersection from a new sphere (converted the sphere to NURBS surface). That Solid Intersection has no fill? Convert to NURBS surface, still no fill, but click it with the Split tool (point mode) and the surface fills. ??? This object can be shelled, then duplicate in place then 3d rotate the dupes around drawing origin. Add Solids and Convert to Generic makes the screen navigation work better.

 

I have to play with the rotations and also see how dense the client wants this.

 

Getting there.  No hurry. This street improvement project is sluggish, likely to pick up when the weather gets bad.  I mean, what's the point of travel to meetings or site work without rain, snow, ice, wind, etc?

 

-B

 

Ball o' Twine2.png

  • Like 2
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...