PHYSICSTENSILE STRUCTUREEXPLORATION OF TENSILE STRUCTURE THROUGH THE USE OF DIGITAL SIMULATIONS. MESH TENSION AND FUNICULAR STRUCTURES WILL BE EXPLORED.

BEFORE WE BEGIN! Please install all necessary programs and plug-ins before continuing with this tutorial. Please follow their respective installation guides that are provided. All plug-ins are free for download.

Rhino 3D

Grasshopper

Kangaroo Physics

Weaverbird

Funicular structure definition

Kangaroo Physics is a Live Physics Engine Plug-in for Grasshopper that is used for interactive simulation and form-finding of meshes in Rhino. It can be used for structural analysis with real-time visual feedback as you change various inputs such as the speed, stability, or strength. Kangaroo Physics will allow you to run different dynamic simulations for different design purposes by using particular forces such as Unary force, Bending force and Spring forces that are applied onto particles or meshes. Though Kangaroo can simulate physics on an object, it is only limited to Meshes and cannot measure the exact amount of force being applied that could transfer into real life possibilities.

In this particular tutorial, we will be exploring tension caused by gravity and spring forces that are being applied onto meshes. The simulations will show how different forms of meshes will react to different inputs placed in the Kangaroo Physics Engine, creating various possible forms.

Eric Wong, Jian Zhou Sun, Michael Kwan

The simulation is conducted within Rhino. To run simulation open Rhino. 01

Tensile Structure Simulation through gravity

Since the simulation definition requires mesh surfaces to operate we will need to create them. To do so, draw a normal

nurbs surface in Rhino (this surface will be the bases of your tension simulation).

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Type in “mesh” within the Rhino command bar, press “enter”, and then select the surfaces you want to convert into mesh

surfaces, then finish by pressing “enter”.

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With surfaces made, we will need to set anchor points so that when the simulation is conducted, these points will be

where the tension originates. These points will not move as the simulation is conducted. Type “points” in the Rhino command, then select the points you wish to be anchor points within your model space. The points do not need to be within the mesh area or on the edges of the mesh.

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Load Grasshopper and the Funicular structure definition.

Funicular structure definition can be found here:http://www.grasshopper3d.com/group/kangaroo/forum/topics/funicular-structures-2

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When the definition is loaded scroll over to the first “mesh” component. Right click and choose “set one mesh” or “set

multiple mesh”. As the name suggests “set one mesh” will only allow one mesh surface to undergo the simulation where as “set multiple mesh” will allow several mesh surfaces to go through simulation.

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You will then be transferred back over to the Rhino model space. Choose your mesh surfaces now, hit “enter”

to finish. You will be brought back into Grasshopper.

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Find the “pt” component right click it, and you will be brought to a similar menu as the previous step. Select “set

one point” or “set multiple point” depending on how many points you wish to be anchor points within your simulation.

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After the menu selection, you will again be transferred over to Rhino. Choose your anchor points. If you had chosen

“set multiple point” you can highlight multiple points for quicker selection. Hit “enter” when complete. You will again be transferred back into Grasshopper

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Find the “kangaroophysics” component (Kangaroo Physics Engine) right click on the force object and click “flatten”

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Find the “toggle” component and toggle to “false” your mesh should now be undergoing the simulation.

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To adjust the parameters of the simulation, you can adjust the slider and or the interval component. Negative value

within the slider creates a drooping simulation, and a smaller interval creates a quicker drop in simulation.

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Positive slider number

Negative slider number

Anchor points do not have to be on the mesh itself. It can be anywhere on the model space. As well, the higher the definition of the mesh (larger polygon count) the more accurate and precise the mesh tension will be simulated when acted with gravity. The following images demonstrates each respectively.

Additional Information

Anchor points within mesh

Anchor points outside mesh

Low density of vertices

High density of vertices

Create a mesh in Rhino by selecting “mesh” in the tool-bar, then “polygon mesh primitives”, then “plane”

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Tensile Structure Simulation through internal tension (spring)

Create four points on the corner of the mesh by typing “point” in the Rhino command02

Go into Grasshopper and double-click on the canvas and type in “mesh” and select the “mesh” component. Assign

the mesh component to the Rhino mesh by right-clicking and selecting “set one mesh” in the “mesh” component. In the Rhino model space, click on the mesh you have created and it will bring you back into the Grasshopper window (the mesh in Rhino is now assigned to the “mesh” component). Double-click again on the canvas in Grasshopper and type in “point” to bring up the “pt” component. Assign the

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“pt” component to the points created in Rhino by right clicking and selecting “Set multiple points”. Select every point in the Rhino view port and press enter.

Double-click on the Grasshopper canvas and type in “springsfrommesh” and select the component. Connect

the “mesh” component to the “mesh” section in the “springsfrommesh” component.

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Double-click on the Grasshopper canvas and type in “kangaroo” to select “kangaroophysics” component.

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Connect the “mesh” component and attach it to the “geometry” section of the “kangaroophysics”

component. Connect the “pt” component to the “anchorpoints” section of the “kangaroophysics” component.

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Double-Click on the Grasshopper canvas and type in “slider” and select “numberslider”. Duplicate

the slider by copy and pasting into the Grasshopper canvas. Select one slider and connect it towards the “stiffness” section of the “springsfrommesh” component. Select the other slider and connect it to the “restlengthfactor” section of the “springsfrommesh” component. Connect the “springsfrommesh” component to “forced objects” section of the “kangaroophysics”.

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Double-Click on the Grasshopper canvas and type in “toggle” and select the “booleantoggle” component.

Double click on the grasshopper canvas and type in “timer” and select the “timer” component. Connect the “booleantoggle” component to the “simulationreset” section of the “kangaroophysics” component. Connect the “timer” component to the “kangaroophysics” component. Double-Click on the Grasshopper canvas and type in “mesh” to select the “mesh” component. Connect the “mesh” component to the “geometry out” section of the “kangaroophysics” component.

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Double-click on the “booleantoggle” component (From True to False) to start the simulation of the mesh in Rhino.

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Manipulate any of the four anchor points in Rhino and/or the two sliders in Grasshopper to change the simulation on the

Mesh.

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Once satisfied with the shape of the mesh, right click on the “mesh” component that is connected to “geometryout”

and select “bake” to finalize the form in Rhino.

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