how to modelize an helix shaped ring using rhino's udt...

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Rhino 3D

How to modelize an helix shaped ring using Rhino's UDT and history

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How to modelize an helix shaped ring using Rhino's UDT and history

The goal is to create an helix shaped ring using Rhino's History and UDT commands, in order to fasten the modelization process and help to adjust

the size and shape of the ring.

Also it will be much more easy to place gems onto the ring.

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Creation of the helix

- draw a line starting from origin, L=10- draw an helix around the line

- Radius = 8,6- 1,2 turns

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Extrude a surface from the helix.

- select the option "Direction" and click the start and end points of the line to set de extrusion direction.

- extrusion distance = 5mm but the value isn't very important.

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For a better visibility during the further modelization process it's better to move the surface (in ortho mode) along Y axis. Let's say 20 mm

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Now we'll create a planar surface representing the "unrolled" helix surface.

- From the menu Curves > Curves from objects select Create UV curves- this curves are automatically placed at the origin od the Cplane (grid).

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- Move this rectangle from 15 mm along Y axis to improve the visibility (no matter the distance).

- Put a planar surface starting from this rectangle (Surface > from planar curves )

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Now, we'll put a dot to mark the surfaces origin and orientation.

- Menu Analyze > Direction , click on the planar surface. The arrows show the surface directions U (in red) and V (in Green), and also the normal (in white).- Put a Dot (Dimensions > Dot) at the origin of the surface.

- Repeat the same operation for the helix shaped surface and put the dot at the origin.

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Now it's possible to draw the section of the ring

- Select the Right view and draw a rectangle (5 x 2 mm). Dimensions are not critical.

- Explode the rectangle and replace one side by a Arc 3 points. Join the curves to get a close polycurve.- Move this contour from a distance equal to the one from the helix curve to the middle of the helix surface. (17,5 mm in the example)

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Now, we can choose 2 different ways:

A - Use Loft command

B - Use "Cage" tool

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Copy the previous contour along the planar surface : end points and midpoint.

It's possible to increase the numer of copies to get more possibilities to adjust the final shape.

A - "Loft" method

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Important :Rhino's history must be activated. Right click in the "History" box of the status bar, and select "Always record history"

A - "Loft" method

- Now create a loft surface from the 3 planar sections. Menu Surface > Loft- select the 3 curves through a windows and accept default options.

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History being activated, if a section is moved, the lofted surface is automatically updated.

Example:

A - "Loft" method

Now we will use this great rhino's feature combined with FlowAlongSrf command to adjust the final shape of the ring.

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Now we can "roll" the previous shape around the helix, using Rhino's UDT commands (Universal Deformation Technology)

A - "Loft" method

Menu Transform > Flow along Surface. - select the shape and confirm (Enter)- select the base surface near a corner. Click near the dot we put previously. - select the target surface cible by clicking near the "same" corner, marked by the dot.If you select another corner on, the commands works but the result may be not as expected ! This is why we put previously the dot.

The planar shaped is not closed (not a solid) so the target shape is not closed also. This will be done at the end of the modelization process, when the right final shape will be done.

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Because History apply also to "FlowAlongSrf" command, if you modify one of the initial sections, the helix shaped ring is automatically updated.

- To adjust the sections use Scale1D ou Scale2D, or if present the Gumball, or better the Tspline manipulator.

- To obtain the shape shown on the picture, you must decrease the width of start / end section and decrease the Height of middle section (Scale1D)

A - "Loft" method

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2nd method.

A - Use "Loft" command

B - Use "Cage" tool

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From the 2D contour, make a linear extrusion

- Menu Solid > Extrude planar curves > Straight- select the contour and extrude it along the plane length.

B - "Cage" tool method

The result is a closed solid.

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Now we can "apply" this solid to the helix shaped surface using FlowalongSrf command.

Menu Transform > Flow along Surface. - select the shape and confirm (Enter)- select the base surface near a corner. Click near the dot we put previously. - select the target surface cible by clicking near the "same" corner, marked by the dot.If you select another corner on, the commands works but the result may be not as expected ! This is why we put previously the dot.


Important :Rhino's history must be activated. Right click in the "History" box of the status bar, and select "Always record history"

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Because History apply also to "FlowAlongSrf" command, if you modify the initial shape, the helix shaped ring is automatically updated.To modifiy the source shape we will use the Rhino's UDT "Cage" tool

- Menu Transform > cage editing > Cage edit.

- select the captive object (source object)- select "BoundingBox" option, then "World" coordinate system- define the desired number of control points in each direction. Start with X=3 Y=2 and Z=2


- accept default option

The source object is now constrained in a cage with control points.

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It's easy to modify the source object by dragging / moving the control points. Thanks to the history, the target object (helix shaped ring) is automatically updated.

- the cage points can be also modified using Scale factor.- the Gumball tool or Tspline manipulator are also great to modify control points.- It's also possible to use Transform > Move UVN tool to modifiy control points. In this case, U, V, N indication of the dialox box must be read as X, Y, Z. The "Scale" is the amplitude of displacement for each click on X,Y, Z arrows. If necessary use "Symmetry U" and "Symmetry V" to move control points using X or Y symmetry.


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Move control points along X,Y, Z axis to adjust the final shape of the ring.

- Be careful, in case of mistake it's better to use "Undo" instead of making the opposite displacement. .- It is strongly suggested to save the undeformed model before starting the cage editing. - Adding more control points to the cage allow more localized adjustements of the final shape.


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Using one of the 2 suggested methods we have the general shape of the ring. Now it's time to make some improvements, filleting and also add gems.

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To change the size of the ring (finger size) it's enough to move vertically (along Z axis) the planar shape along Z axis. FlowAlongSrf apply to a distance equivalent to the one from the planar shape to the source planar surface.

Change the size of the ring (finger size)

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To modify overall width, it's enough to adjust the width of the target surface using Scale1D command. All modifications of the source object remains active and apply on the final shape.

Change the overall width

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To add gems, you can place them on the planar source object and use FlowAlongSrf to apply the gems to the final shape.

Thanks to the pwerful Rhino's history, it's easy to accurately place the gems on the final helix shaped ring.

Add gems

- Place the gems on the source object using RhinoGold Gem Studio or by importing an existing .3DM model.

- Apply the UDT FlowAlongSrf command, but set the option Rigid=Yes to avoid gems distortion.

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- The adjust the position of the gems using Drag / Move / Rotate commands- The height adjustment is done by moving the gems along Z Axis.- It's also possible to change gem size using Scale3D command.- Gumball tool (if present) or TSpline manipulator are a great help for a fine tuning of the gems position.

Add gems

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Now it's time to finish the ring :

- Fillet or Blend edge- Boolean operation

- Be careful, as soon you modifiy the target object (final ring) the history is lost, and the further modifications become much more difficult !

- It's strongly suggested to Save As the model or put a copy on another layer before starting the fintion of the ring.

Finishing the ring

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Final Keyshot rendering

Diapo 1Diapo 2Diapo 3Diapo 4Diapo 5Diapo 6Diapo 7Diapo 8Diapo 9Diapo 10Diapo 11Diapo 12Diapo 13Diapo 14Diapo 15Diapo 16Diapo 17Diapo 18Diapo 19Diapo 20Diapo 21Diapo 22Diapo 23Diapo 24Diapo 25Diapo 26Diapo 27Diapo 28

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