rhinoVAULT Quick Reference for rhinoVAULT Beta Version 0.2 2012-05-10
by Matthias Rippmann Lorenz Lachauer Philippe Block
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1
Introduction..................................................................................................................................................................................... 3
2
Technical Requirements and Installation ....................................................................................................................................... 4
2.1
Requirements ................................................................................................................................................................................. 4
2.2
Installation....................................................................................................................................................................................... 4
2.3
Tool Package .................................................................................................................................................................................. 4
3
The Tool ......................................................................................................................................................................................... 4
3.1
Layer Structure – Data Handling in RhinoVAULT ........................................................................................................................... 6
3.2
RhinoVault Settings - rvSettings ..................................................................................................................................................... 6 3.2.1
Vault Height Scale – Changing the Overall Height of the Vault ............................................................................................. 7
3.2.2
AngleTolerance – Maximum Deviation Tolerance Angel between Form and Force Edges .................................................. 7
3.2.3
EdgeMin / EdgeMax – Control the Lengths of the Form and Force Edges .......................................................................... 7
3.2.4
Iterations and Step Size – Control the Max Iterations and Step Size of Iterative Procedures ............................................... 7
3.2.5
High Precision/Runge Kutta 4th Order – Changing the Type of Solver .................................................................................. 7
3.2.6
Show Color Analysis/ Show Mesh /Show Pipes – Visualize the Three-Dimensional Result .................................................. 7
3.3
Generate Form Diagram - rvForm .................................................................................................................................................. 7
3.4
Generate Dual Graph - rvDual ........................................................................................................................................................ 8
3.5
Relax and smoothen the Form Diagram - rvRelax ......................................................................................................................... 8
3.6
Modify Diagram - rvModify ............................................................................................................................................................. 8 3.6.1
Move/Scale2D/Scale1D/Bend - Manipulate the Form and Force Diagram to Change the Thrust Network ......................... 8
3.6.2
Supports – Manipulate the Supports ..................................................................................................................................... 9
3.6.3
Openings – Define one or more Oculus ................................................................................................................................ 9
3.6.4
NodeWeight – Change the Inertia of Nodes ........................................................................................................................ 10
3.7
Horizontal Equilibrium - rvHorizontal ............................................................................................................................................ 10
3.8
Vertical Equilibrium - rvVertical ..................................................................................................................................................... 11
3.9
Info ................................................................................................................................................................................................ 11
4
Additional Information .................................................................................................................................................................. 11
5
Copyright ...................................................................................................................................................................................... 12
6
Contact ....................................................................................................................................................................................... 12
7
Acknowledgements ...................................................................................................................................................................... 12
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1
Introduction
This is the quick reference for the plug-in RhinoVAULT Beta Version 0.2 for Rhinoceros® 4.0 with SR 9.0 or higher for Windows. It is a form finding tool to intuitively design compression-only, vaulted structures. It can be seen as a hanging chain model but then a more controllable, flexible and comprehensible digital version. The tool is based on the Thrust Network Approach – TNA, which is described by P. Block in his Ph.D. dissertation Thrust Network Analysis: Exploring Three-dimensional Equilibrium at MIT, Cambridge, MA, USA in 2009. The method uses the two fundamental elements of graphic statics: -
Form Diagram
-
Force Diagram
Fig.1-1. Form (left) and Force (right) diagram in the x,y-plane
The form and force diagram are in horizontal equilibrium, which means that corresponding edges in both diagrams are parallel and properly orientated. Based on the configuration of both two-dimensional diagrams, the calculation of the vertical equilibrium results in a three-dimensional thrust network, which represents the shape of the compression-only structure.
Fig.1-2. Three-dimensional thrust network representing the compression-only structure
In simple terms, the form diagram defines the perimeter and force pattern, representing the predefined “flow of forces”, of the vault design in plan. The force diagram defines the horizontal force components in the structure, and how they are proportionally distributed/related. RhinoVAULT was developed to generate, shape and adapt the user’s design by manipulating both diagrams in a
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bidirectional and interactive manner. The Rhino plug-in is based on current research done by the BLOCK Research Group at ETH Zurich, Switzerland on structural form finding using the Thrust-Network-Approach (TNA) to intuitively create and explore compressiononly structures. Our goal is to share key aspects of our research in a comprehensible and transparent setup, to let you not only create beautiful shapes but also to give you an understanding of the underlying structural principles. The plug-in is still in its beta testing phase and under continuous development. Errors and crashes might occur! Nevertheless, enjoy designing awesome structures! Happy form finding!
2
Technical Requirements and Installation
2.1
Requirements
RhinoVAULT Beta is a plug-in for the CAD NURBS modeling software Rhino. It is freely available for download from http://block.arch.ethz.ch/tools/rhinovault. An installed version of Rhino 4.0 with SR 9.0 or higher for Windows needs to run on your system. The evaluation version of Rhino 4.0 can be downloaded for free from http://download.rhino3d.com/rhino/4.0/evaluation/download/. 2.2
Installation
Unzip the package, save the RhinoVAULT_Beta.rhp to your hard disk and drag and drop RhinoVAULT_Beta.rhp to a new session of Rhino. Drag and drop the toolbar RhinoVAULT_Beta.rui (Rhino 5) or RhinoVAULT_Beta.tb (Rhino 4) to an open Rhino session. Toolbars will not show at this point. To view them, you need to go to ->Tools/Toolbar Layout, select RhinoVAULT_Beta and check its menu. Next time you open Rhino, the toolbar will show in your workspace. If there are problems with the installation try to first unblock the file RhinoVAULT.rhp as described here: http://wiki.mcneel.com/rhino/unblockplugin. 2.3
Tool Package
The plug-in features 8 RhinoVAULT-specific commands starting with “_rv�. They can be executed by typing the command name into the command line, by using the RhinoVAULT menu in the top main control bar or by clicking on the specific buttons in the RhinoVAULT toolbar.
Fig.2-1. Toolbar from left to right: RhinoVault Settings (command: _rvSettings), Generate Form Diagram (_rvForm), Generate Dual Graph (_rvDuality), Relax Form Diagram (_rvRelax), Modify Diagram (_rvModify), Horizontal Equilibrium (_rvHorizontal), Vertical Equilibrium (_rvVertical), Info (_rvInfo)
3
The Tool
This section describes the RhinoVAULT commands in the order as they appear in the RhinoVAULT toolbar from left to right. The order of buttons is based on the procedural TNA form finding process, in which first the form diagram needs to be defined, followed by the calculation of the horizontal equilibrium, before calculating the vertical equilibrium to determine the final shape of the vault. If any modification is done to either the form diagram or the force diagram, one needs to ensure to always re-calculate the horizontal equilibrium before calculating the vertical equilibrium. The software will automatically warn the user if the defined, sequential process is violated. The following flow diagram shows the main steps of the design workflow using RhinoVAULT.
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Fig.3-1. Overview of the main steps of the design workflow.
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3.1
Layer Structure – Data Handling in RhinoVAULT
Every single object used to visualize and store the most recent RhinoVAULT result is assigned to a specific layer. This process is automatically controlled by the plug-in and ensures the continuation of a RhinoVAULT project saved as a Rhino files (*.3dm). It is important to keep this layer structure at all time and to keep the layers free of other elements not linked to the RhinoVAULT procedure.
Fig.3-2. The default layer structure of Rhino VAULT for the geometry objects used in Rhino
3.2
RhinoVault Settings - rvSettings The various settings of RhinoVAULT need to be specifically adjusted depending on the complexity, size and density of the form
and force diagram. Most parameters have a significant influence on the smooth generation of a possible form and force diagram in equilibrium and the three-dimensional thrust network. Most often, the default values can be used, but in some cases the adjustment of interdependent parameters needs experience and ideally a basic understanding of graphic statics and structural design. The following default parameters can be changed by the user:
Fig.3-3. The default settings to control the different commands of RhinoVAULT.
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3.2.1 Vault Height Scale – Changing the Overall Height of the Vault The vault height scale factor defines the overall height of the thrust network, i.e. the compression equilibrium solution. A higher number will increase the overall height of the vault. Changing the scale factor is equivalent to uniformly scaling the force diagram in the x-yplane. 3.2.2 AngleTolerance – Maximum Deviation Tolerance Angel between Form and Force Edges This value defines the maximal deviation between corresponding edges of the form and the force diagram. The iterative process to find a parallel and properly orientated configuration of both diagrams will only stop if this deviation falls under the defined angle tolerance (or if the maximum number of iterations is reached). For this horizontal equilibrium a deviation of 5°-10° is usually acceptable for the design stage. A smaller value will increase computation time but will result in a more accurate solution. This value represents the degree of inequilibrium allowed. 3.2.3 EdgeMin / EdgeMax – Control the Lengths of the Form and Force Edges The minimum and maximum length of all edges in both diagrams can be limited. These values can be used to avoid extreme local forces and numerical conflicts due to very small edge lengths during the calculation of the horizontal equilibrium. The values describe the allowed proportion between the minimum and maximum edge length of each diagram individually. 3.2.4 Iterations and Step Size – Control the Max Iterations and Step Size of Iterative Procedures The iterative process to find a relaxed form diagram, to find a parallel and properly orientated configuration of both diagrams in horizontal equilibrium, and to find the three-dimensional thrust network in vertical equilibrium will only stop if the maximum number of iterations is reached (or a certain threshold value e.g. angle tolerance is reached). Heavy computing is used to find a horizontal and vertical equilibrium, which can slow down the overall design process significantly. The maximum number of iterations depends on the density and complexity of the diagram and should usually not be much higher than 600. If more iterations are needed for solving, it is usually better to repeat the process by using the command again. The step size visual value defines the number of iterations passed until the viewport gets updated. To increase the computational speed this value can be set to a number higher than the maximum number of iterations. However, often it is useful for the design process to see the diagrams and thrust network converging towards the optimized configuration. 3.2.5 High Precision/Runge Kutta 4th Order – Changing the Type of Solver Enabling this option affects the solver used to calculate the vertical equilibrium respectively to generate the thrust network. Using the 4th order Runge Kutta solver can speed up the iterative process but it is more likely to cause instabilities during the calculation. 3.2.6 Show Color Analysis/ Show Mesh /Show Pipes – Visualize the Three-Dimensional Result The result of the three-dimensional structure is represented by a spatial network of lines or optional mesh geometry. Enabling the show color analysis function displays a color scheme showing the magnitude of forces in proportion. Moreover, this force distribution can be visualized by a colored mesh and a network of pipes with force-dependent proportions. The minimum and maximum diameter of the pipes can be adjusted according to the scale and size of the form diagram. 3.3
Generate Form Diagram - rvForm The first initial form diagram defines the layout of forces in plan and the perimeter of the vault. The topology of the network can
be chosen freely. Open-end edges define end nodes which will remain their position and thus represent supports of the structure. The form diagram can be drawn manually, generated with the help of internal Rhino commands and external programs, or defined with the build-in RhinoVAULT function _rvForm. It is important to ensure that generated or manually drawn diagrams don’t content overlapping or duplicate edges and that all edges are assigned to the 01_FormEdges layer.
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3.4
Generate Dual Graph - rvDual To generate a possible force diagram based on the defined form diagram, one should first generate the dual graph of the form
diagram. This graph is rotated by 90째 and represents the force diagram in a non-equilibrium state, meaning that corresponding edges are not yet parallel and have not yet the same direction. Numbers (annotation dots) at edges which are not in equilibrium will show the specific angle deviation. 3.5
Relax and smoothen the Form Diagram - rvRelax This option redistributes the form diagram in a way that all edges tend to minimize their length. This globally relaxes the
diagram usually resulting in a smoother solution. The NodeWeight option in the rvModify dialog can be used to specifically control the inertia of individual nodes during the relaxation process.
Fig.3-4. A distorted, poorly distributed form and force diagram (left). A relaxed and smooth form and force diagram (right).
3.6
Modify Diagram - rvModify This command helps the user to perform different modifications on both diagrams and the thrust network. Selectable
modification options are: Move, Scale2D, Scale1D, Bend, Supports, Openings, NodeWeight. 3.6.1 Move/Scale2D/Scale1D/Bend - Manipulate the Form and Force Diagram to Change the Thrust Network Modifications of either the form or the force diagram in the x-y-plane will affect the three-dimensional thrust network. By moving or scaling parts of the force diagram the forces in the structure are redistributed, causing geometrical changes in the resulting shape. Modifying the form diagram will most likely change the perimeter, thus the global shape of the structure. Both diagrams are interdependent such that corresponding edges need to stay parallel and orientated properly during the entire process; only the length can vary. This important requirement for a structurally correct solution will mostly be ensured by the software using the rvHorizontal command. Moving or scaling parts of the diagrams should be done in a way that most edges are only getting stretched without causing a major direction deviation in comparison to the starting configuration.
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Fig.3-5. Modifications of the force diagram which mostly affect the length of the edges in comparison to the starting configuration (grey). Colored numbers (annotation dots) indicate the resulting direction changes of individual edges in degrees.
3.6.2 Supports – Manipulate the Supports By using the Supports feature, the user can manipulate the height of the individual supports. Using the perspective or a side view works best to control the height properly. Use MoveVertical, if you want to move individual supports in z-direction or the Project command to project selected support nodes onto an existing surface or mesh. To add supports which take vertical thrust only, the ToggleSupport command can be used.
Fig.3-6. The defined support nodes can be moved vertically, changing the height of supports in space (left). Inner nodes can be re-defined as support nodes to create a column-like alteration of the thrust network (right).
3.6.3 Openings – Define one or more Oculus Side openings respectively open edge arches of the structure are automatically detected and taken into consideration for the calculation of the vertical equilibrium. The Openings command is used for the definition of openings (oculus) in the structure. It basically changes the applied loads of the nodes surrounding the opening. Enabling the Show Mesh feature in the settings dialog helps to identify openings in the structure.
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Fig.3-7. A typical oculus opening in a vaulted structure before (left) and after the correct assignment (right).
3.6.4 NodeWeight – Change the Inertia of Nodes The NodeWeight option can be used to control the inertia of individual nodes. This affects the rvRelax and the rvHorizontal RhinoVAULT command. To each node of the form and force diagram a value between 0 (fixed) and 1 (free) can be assigned. The default is 1 except for all initial support nodes of the form diagram. 3.7
Horizontal Equilibrium - rvHorizontal The horizontal equilibrium ensures that that corresponding edges of the form and force diagram are parallel and properly
orientated. Thus, the horizontal force components within the structure are perfectly balanced. Since both diagrams are interdependent, changes will always influence both diagrams.
Fig.3-8. Colored numbers (annotation dots) indicate corresponding edges which are not parallel and do not have the same direction. The form and force diagram are not in horizontal equilibrium.
In order to weight the influence one diagram has on its counterpart, the user is asked to weight the influence of the force diagram on the form diagram and vice versa. For example, by setting the value to Neutral, both diagrams will adjust their configuration to find a mean solution. If one wants the force diagram to completely adapt based on the direction of edges in the form diagram one should choose Force100.
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Fig.3-9. In the left image, based on the initial configuration in Fig.3-8, the force diagram is adjusted according to the form diagram with the setting Force100. The process is reversed in the right image using the setting Form100.
The angle deviation value in the settings dialog defines the maximal deviation between corresponding edges of the form and the force diagram. A deviation of 5째-10째 is usually acceptable for the design stage. A smaller value will increase computation time. The specific deviations of corresponding edges will be shown in degrees if the horizontal equilibrium cannot be computed within the defined angle deviation and number of iterations. Some topologies and specific configurations are very constraint, making it impossible to find a satisfactory horizontal equilibrium. One might try this to find a solution:
3.8
-
Use the rvHorizontal command repeatedly (decrease the number of maximum iterations)
-
Relax your Form Diagram again with the rvRelax command
-
Allow the diagrams to move freely. Check for fixed nodes -> rvModify -> NodeWeight
-
Increase the Min/Max Form and Force Edge value in the settings dialog
-
Adjust problematic areas of the diagrams manually using -> rvModify -> Move
-
Start again with a less constrained topology ;) Vertical Equilibrium - rvVertical The result is generated, respectively updated, by an iterative approach based on the horizontal equilibrium of the form and force
diagram. The vertical equilibrium of the forces ensures a compression-only solution under dominant self-weight. The Vault Height Scale value in the settings dialog controls the height of the structure. The solution can be visualized by a network of lines, pipes and a continuous mesh. If the vertical equilibrium fails to fully compute the thrust network will be shown in red. In this case use the rvVertical command again (you might want to increase the maximum number of iterations -> Interations Max Vertical). If you run into instability problems, make sure the Runge Kutta 4th Order solver is deactivated in the settings dialog. 3.9
Info Guides you to the RhinoVAULT website, where you can learn more about the plug-in and the used methods.
4
Additional Information
The tool was developed to support the user in the form finding process of vaulted compression structures in the early design phase. It is obvious that prior to any realization of structures based on designs obtained with RhinoVAULT, a detailed structural analysis is necessary.
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5
Copyright
The development of RhinoVAULT is currently supported by the BLOCK Research Group at ETH Zurich, Switzerland. It is shared freely in the hope that students and professionals will enjoy it and use it for original and creative work. It can be freely shared and used for academic and commercial purposes, but with proper attribution. This work is licensed under: Creative Commons - Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) http://creativecommons.org/licenses/by-sa/3.0/ -
Matthias Rippmann (project leader)
-
Lorenz Lachauer
-
Philippe Block
BLOCK Research Group, ETH Zurich, Switzerland http://block.arch.ethz.ch
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Contact
Dipl.-Ing. Matthias Rippmann | Research Assistant Assistant Chair of Building Structure | Prof. Dr. Philippe Block ITA - Institute of Technology in Architecture ETH Zurich Wolfgang-Pauli-Str. 15, HIL E 45.2 8093 Zurich, SWITZERLAND T F E W
+41 (0)44 633 28 03 +41 (0)44 633 10 41 rippmann@arch.ethz.ch www.block.arch.ethz.ch
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Acknowledgements
The authors would like to thank Diederik Veenendaal for his assistance in implementing the 4th order Runge Kutta solver, Ramon Weber for his contribution to the tutorial material and beta testing and Tom Van Mele for creating the rhinoVAULT tools page under the http://block.arch.ethz.ch domain. In addition we would like to thank our workshop participants for their patience and feedback during the first phase of development.
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