Benson Shaw

Draw on a sphere

20 posts in this topic

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

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Hi, You can get this using a bump effect. As sure with a bit more fiddling you could probable get a result that gives the appearance.

Am sure more options available , need a bit of thought to see what is possible

Capture.JPG

Light.vwx

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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

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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.

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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

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Benson,

I was having some trouble with Shell geometry recently. If you're trying to create a hollow sphere with thickness, I would recommend using a solid subtraction with two spheres instead.

 

This process is fascinating to watch....... its the sort of thing someone would ask me to do too.

 

Kevin

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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

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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

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2 hours ago, Kevin McAllister said:

I love the look of this result!!

don't you feel like you just want to grab with your hands & squash it?

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Remember Islandmon give him a holler - he'd definitely be into this.

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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

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This Marionette network gives you the points on a sphere to select, The challenge now is to get the EAP to choose them automatically and draw line.

You can manually choose the points to draw a Nurbs curve.

adjust the number of points and radius as desired. Will play more

Capture.JPG

Draw on Sphere.vwx

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This Marionette object you can use as it places locus points on the sphere for you to join the dots. you will get division error when you change a number but just ignore each time and the object will appear, will fix later. Still to look at auto EAP between nodes.

Draw on Sphere_001.vwx

Capture.JPG

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I think you're definitely on the right track with this one Alan

Try a second and third sphere with slightly increasing radii and use the outer loci for the crossovers.

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Posted (edited)

Further What I did here was to choose points around the sphere while rotating then EAP, (you may get error so i cut into sections) then once you have one good set use duplicate array (circular to get more. HTH will play more

Clip cube shows the lines around the sphere better.

Capture.JPG

Draw_on_Sphere_002.vwx

Capture.JPG

Edited by Alan Woodwell
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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

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Posted (edited)

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
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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

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1 hour ago, Benson Shaw said:

 

Ball o' Twine2.png

Lots of nice shapes in this version!

KM

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