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3D Modeling Interface With Air Spray: Field Study of 3D Model Making and Prototype Development

CHI 2005 | alt.chi April 2-7 | Portland, Oregon, USA 3D Modeling Interface with Air Spray: Field Study of 3D Model Making and Prototype Development Hee-kyoung Jung, Tek-jin Nam, Ho-sung Lee CIDR (Collaborative & Interaction Design Research) Dept. of Industrial Design, KAIST, 373-1, Gusung-Dong, Yusung-Gu, Daejeon, 305-701, Korea {hkjung, tjnam, aleclipse} ABSTRACT This paper presents a novel interface for 3D modeling in augmented reality, aiming at developing a form gradually in t
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  3D Modeling Interface with Air Spray: Field Study of 3DModel Making and Prototype Development Hee-kyoung Jung, Tek-jin Nam, Ho-sung Lee CIDR (Collaborative & Interaction Design Research)Dept. of Industrial Design, KAIST, 373-1, Gusung-Dong,Yusung-Gu, Daejeon, 305-701, Korea   {hkjung, tjnam, aleclipse} ABSTRACT This paper presents a novel interface for 3D modeling inaugmented reality, aiming at developing a form gradually inthe early phase of a product design process. PreviousVR/AR based modeling systems have focused largely ongeometrical algorithms and system performance issues.From a designers’ perspective, this study analyzed theconventional form creating processes and developed a moreintuitive and designer-friendly modeling interface. Basedon the understanding of various form-making methods andtools, we suggest the concept of “spray modeling” interface,which adopts a real air spray gun as an input device. Itallows the user to create a 3D frame and to spray virtualfoam around the frame as in a sculpturing process. It alsoprovides coherent sound and air-force feedback. As ametaphoric approach for novel modeling interface, spraymodeling is expected to be widely applied to humancomputer interaction researches beyond design modeling. Author Keywords 3D Interface, Interactive Modeling, Augmented Reality,Computer Aided Industrial Design, Computer AidedGeometric Modeling ACM Classification Keywords H.5.2 [User Interfaces]: Prototyping, D.2.2 [Design Toolsand Techniques]: Evolutionary prototyping, H.5.1[Multimedia Information Systems]: Artificial, augmented,and virtual realities, J.6 [Computer-Aided Engineering]:Computer-aided design (CAD) INTRODUCTION Creative ideation and quick expression of conceptual formsare required in the early phase of design process. Designideas evolve through iterative visualization andembodiment [2, 5], which provokes further ideation anddialogue between members in a design team [18]. As thesesteps are closely tied with each other, efficient tools andmethods for the form making process is important toimprove the quality of the final outcome. Designers needintuitive tools that inspire their imagination. Current 3D Modeling Interface Desktop-based computer aided design (CAD) modeling iswidely used as model simulation tools. However, they haveproblems of complex user interface. They are operated in a2D display with 2D input devices, while designersconceptualize objects in a three-dimensional space. Thisincurs conflicts between the user’s mental model and thesystem model [4].Moreover, when using a CAD modeling system, designersare forced to build models from geometric components suchas vertex, curves and surface. This modeling sequence iscaused by the system-oriented data structure. It is difficultfor designers to start modeling in these CAD systemswithout having the clear picture of the final form.Alternatively, virtual or augmented reality based three-dimensional modeling systems have been introduced tosolve the dimensional difficulties of current user interfacein desktop based 3D modeling. However, they are mostlyevolved from technology-oriented approach lacking inunderstanding of the shaping process. Many studies inVR/AR focused on the interface of navigation inconstructed VR environment rather than the real-timemodeling process, which is more necessary in design work. The Objective of the study The objective of this study is to suggest a novel 3Dmodeling interface, which enable users to think intuitivelyand express their ideas. Emphasizing the users’ mentalmodel and their natural behavior, we ultimately aim at 3Dmodeling interface for the conceptual design phase of thedesign process. For the intuitive manipulation of 3D virtualmodels in space, we use AR environment and reflect theobservation from field studies to a concept-modelinginterface. RELATED WORKS A number of CAD systems and interface methods havebeen developed since digital technologies have beenbrought into the design process. [8, 14, 15] adopt free handsketching behavior for 3D modeling interface. 3D Sketch[14] converts a planar image to a 3D geometric model withcorresponding views and sequences of sketch strokes.Teddy[8] automatically generates a spherical 3D geometry Copyright is held by the author/owner(s). CHI 2005, April 2–7, 2005, Portland, Oregon, USA.ACM 1-59593-002-7/05/0004.   CHI 2005 | alt.chiApril 2-7 | Portland, Oregon, USA 2162  from a sketched image. Qin et al. based on fuzzyknowledge, presuppose an approximate geometric modelfrom a given line sketch [15]. In spite of the considerationfor designers’ familiarity with sketch interface, these arebased on two-dimensional manipulation. The system onlydeals with box-shaped or closed round forms and requiresaccurate interpretation of every line stroke, which might beambiguous in some cases.[6, 7, 21] extended the line sketches into the three-dimensional space. Digital Tape Drawing[6], which isspecially developed for automobile design, allows users tocreate line curves in all six faces of the cubical space. Thecurves are assembled into a complete 3D model. Similarly,Shape Tape[7] adopts a flexible band as a physical mediumfor editing virtual curves which compose the 3D model.These three-dimensional sketching systems introduce aunique interface of their own. However, these methods aremore appropriate for the later phase of modeling. Designerstend to start shaping ideation not from line curves but fromrough and unclear shapes.Many studies [3, 13, 20] focus on geometric modelingalgorithms. Singh suggested the interactive digital FrenchCurve, which has been used conventionally in high quality2D drawings or 3D sculptures [20]. It serves as aninteractive guide for curve editing, but high dexterity isrequired to manipulate the intricate curve components. [3,13] employ a modeling metaphor based on the persuasiveprinciples of model-making process. However, users mayfind it difficult because these processes usually underlie theactual user interface. While many researches focus on themodeling algorithms, the study of corresponding physicalinterface is rarely explored.There have been researches on VR/AR-based 3D CADsystems. 3DRAW [16] is a virtual line-sketching systemusing 3D tracking pointers. Surface Drawing [17] enables adirect hand-manipulation of a virtual model by generatingsurfaces with gesture recognition gloves. It supportsfreeform surfaces with natural and intuitive interface, but itneeds more active feedback to guide accurate spatialinteraction. Virtual Sculpting[12] adopts sculpting methodswith haptic feedback using a PHANTON TM device, but itsapproach mainly aims at system implementation withoutconsidering the creative aspects of design ideation. FIELD STUDY We conducted a field study of various modeling works tounderstand formative principles and to get inspiration forinterface concepts. The concerning area of observationranges from practical design modeling to artistic craft suchas clay modeling, wood carving and glass craft. 3D CADmodeling process was also investigated to find out theproblems involved in using existing CAD systems. 3D Modeling Process in a CAID Course We observed the 3D CAD modeling process in anundergraduate course of Computer Aided Industrial Design(CAID) in KAIST with Students who had practiced AliasStudio Tools TM for a month.Before creating 3D models in the computer, they underwentsketching to search an optimal shape estimating functionaland aesthetic requirements. They created a series of outlinedrawings repeatedly. After deciding a rough shape, theystarted CAD modeling from a simple mass of 3D geometryand continued adding details on it (see Figure 1). Severalmodel variations were compared and iteratively refineduntil the final shape was determined. In this course, it wasfound that sketching and modeling were not effectivelylinked. Ignoring the details on the sketches, students oftenimprovised for detail modification in 3D models. It mightbe because the realistic visualization in CAD modelinghelped for a more active concept development.Typical modeling functions, such as extrude, loft, or sweep ,which define the shape of profiles and then pass themthrough a linear path, were frequently used (see Figure 2).These methods support the creation of an initial mass, onwhich additional details would be added or subtracted. It isappropriate for organic and free-form modeling butdemands well organized form-construction planning beforemodeling. The expression and modeling method wereheavily dependent on the methods of the CAD software.Consequently, the modeling results tended to be similaramong students because they all used similar functions.Students had much trouble in dealing with the Boolean operation, which is used for assembling, intersecting orsubtracting separately generated surfaces. The functioninvolved quite a complicate operation. Users had to pre-calculate the output before expressing conceptual ideas. Weobserved that this limitation prevented active formexperiments and that students did not make the most use of the CAID tool for their ideation. Design Model-Making Designers also use physical materials to simulate or developtheir conceptual ideas. Depending on the characteristics of each modeling process, appropriate methods and tools havebeen devised. Paper or cardboard is widely employed atfirst steps, because they are simple and easy to deal with. Figure 1. Adding details on 3D modelFigure 2. Surface modeling method (sweep, Boolean) [1] CHI 2005 | alt.chiApril 2-7 | Portland, Oregon, USA 2163  More feasible materials like expanded resin, clay or wood support effective solid model making. At later steps, surface processing is generally used, because highly realisticappearance is necessary to examine design features beforegoing into production. Thermoforming modeling Thermoforming of plastic material is a popular method to present smooth surface of design models. While this is used for delicate finishing rather than for creative ideation, itoffers useful process and methods, which can be borrowed at the stage of early idea expression. A model-maker first prepares a basic wooden form. Then s/he covers it with aheated plastic plane that is easily deformed due to itsthermoplastic feature. After the plastic plane is spread alongthe surface of the basic solid model, it cools down and hardens to the deformed shape (see Figure 3-1). Severalseparate parts fabricated in this way can be assembled into awhole shape. The method of generating a smooth surface based on the initial solid form can be linked to the step of refining and it can also be applied to develop a given form by deforming the surface. Spray coloring Spray coloring is done at the final step to complete a physical design model. Connected with an air compressor, aspray gun gives out paints together with compressed air.Then the pigments are set on the surface of the completed model. Spray coloring offers useful methods that can beapplied to the refinement of rough models. The structure of a spray gun and its gesturing manipulation provide avaluable concept for spatial interaction in 3D modeling.Spraying distance and angle are mainly related to thesurface size and shape of an object. Varying the amount of air and paint can determine the texture expression of asurface. For example, if a user sets the device to give outmuch paint and little air, then the surface will seem to becorroded with particle clots. These factors can be flexiblyadjusted with controllers and valves on the spray gun.The spatial gesture of an expert model maker is quitedexterous along the targeting surface of an object. They use both hands; the main one for spraying and the other one for fixing the objects. As it is not facile even for them to makedelicate gestures in empty space, the spraying pattern isalmost always simple and repetitive. They just make up-and-down or right-and-left moves within a short range. Therole of fixing and rotating the object serves as the guidancefor spraying gestures previously mentioned, turning theobject to its surface that is to be sprayed (Figure 3-2). Physical Form-Making in Craft Works Traditional physical form-making works have their srcinal processes and tools. We analyzed each work in order tounderstand formative processes and to develop user-friendly interface concepts, reflecting familiar working behaviors. Clay modeling Clay modeling undergoes through attaching and detachingclay benefited from the material’s viscosity. A wire or wood is often used for constructing an initial frame. Theoverall form develops based on the initial frames and then by bending them slightly, an artist can deform the entireshape as the clay around the frame follows the change (seeFigure 3-3).The viscosity of clay also allows quick sketch on the modeland easy modification by rubbing the surface. This “sketchon the surface” is an easy and effective interface for activemodification and form development. We observed that anartist easily repeatedly marked and erased sketches on themodel by rubbing the surface. This flexible process of sketching directly on the surface influences activeformative experiments. Wood carving Compared to clay modeling, wood carving is moreappropriate for detail expression than active ideation. The process consists of repetitive small cuttings and they areaccumulated to create a desired shape. Artists employvarious tools like chisel and knives to carve a detailed shape.They select the right tool among many for a specific type of cutting (Figure 3-4).The sketch for modification is often drawn directly on themodel. However, the artist was more careful to carry outactual carving compared to the case of clay modeling, because cutting is irreversible in wood working. This meansthat formative ideation is largely influenced by the processand material of modeling. Additionally, experts say thatconsidering the type of wood is important because of thetactile feeling when carving. This implies that delicatefeedback is crucial when controlling carving wood. Glass craft  Unlike the previous modeling or carving, glass craft does Figure 3. Physical model-making works3-1.thermoforming modeling, 3-2.spray coloring, 3-3.clay modeling, 3-4.wood carving, craft (from left to right) CHI 2005 | alt.chiApril 2-7 | Portland, Oregon, USA 2164  not directly handle the whole solid but is based on surfacedeformation. An artist deforms the shape by changing thematerial’s chemical state. As s/he heats certain parts of theglass surface, the area changes to liquid and then can beexpanded as s/he blows into it (Figure 3-5). Separate simpleshapes can also be assembled flexibly by heating the area tobe attached.This modeling method is similar to that of thermoformingmodeling and spray coloring because it all goes through adeformation of a given surface. Therefore it can also be of reference to refining interaction in the later steps of modeling. Additionally, division of roles between twohands was exhibited. One hand mainly deforms the surfaceby pulling or pressing the surface with devices while theother continuously rotates the model with a kind of aportable lathe. INITIAL FINDINGS AND INSIGHTS The field study shows that every kind of model-makingprocess has its own characteristics according to the methods,tools and materials. We can apply these methods and toolsselectively to a novel concept of 3D modeling interface,considering the objective to support the early stages of design modeling.Through observation of the CAD modeling course anddesign model-making works, we identified that it isdesirable to support both flexible ideation and effectivevisualization in product design modeling because therealistic representation influences the user’s perception.Consequently it helps active ideation for the formdevelopment as well as making the process more flexible.For example, although clay modeling is the most flexible tomake and change the shape, it is not efficient in expressingdetail due to the difficulties in delicate cutting and surfacepolishing. For ideal design modeling, which allows bothactive ideation and effective expression of these ideas, theinterface can be devised through a reasonable combinationof each modeling method.We derived applicable concepts from various model-making works and then categorized them according to theprocedural characteristics. Table 1 shows 3D modelinginterface concepts developed from the observation of eachphysical model-making method.Based on this approach, we summarize the guidelines of 3Dmodeling interface concept for an initial conclusion of fieldstudies. Direct Sketching on Models We found that the integration of ideation and its expressionare crucial for intuitive modeling and that they aresupported by 3D sketching directly on the surface of physical models. Though the planar 2D sketch is a quick and simple method, it is not appropriate in physical or 3DCAD modeling because the ideation is dissociated from a3D model. Direct manipulation of the real model cansupport both intuitive interaction and immediate perceptionof form developing process through corresponding tactilefeeling on the model surface as well as its visual changes. Methods Applicable interface concept Clay modeling  frame construction  additive modeling  rubbing, indenting  sketch on the surfaceWood carving  detailing for by cutting out  using various carving knives  sketch on the surfaceGlass craft  blowing surface  two-hand manipulation  assembling by heatingThermoforming  surface deformation  use of basic form  assembling separate partsSpray coloring  spraying particle  attaching particles on surface  spraying gesture in space  two-hand manipulation Table 1. Physical model-making methodsand their applicable interface concepts The form should be created, modified and expressed indirect relation with a 3D model in space. The perceptionand the expression activate each other through iterativeinfluence. Simple and Repetitive Manipulation The form develops through continuous evolution from aninitial shape in physical modeling. The manipulation isalmost simple and repetitive like adding, cutting, or rubbing.They are different from specified commands of CADmodeling, such as sweep, loft or extrude. The deformationis carried out by the accumulation of continuous smallchanges. Therefore it is important to suggest manipulationas simple and consistent as possible for intuitive modeling.Additionally, two-hand interaction should be consideredwith the main one for modeling manipulation and thesubsidiary one for positioning the model in space. With thehelp of this assistant positioning, only the main hand has toconsider simple manipulations like adding or cutting. Combination of Molding and Carving Molding is an additive form-making method, in whichadditional mass is attached to previous ones. It is deeplyrelated with the viscosity or adhesion of the main materials.While it supports constructive formation and iterativeevolution, the shape tends to be too blobby as in the case of clay modeling. Therefore, the additive modeling method isappropriate for generating basic shapes in the earlymodeling stage. Once the basic shape is formed, someregulated modification should be followed to refine theform. Additionally, the use of frame construction serves as CHI 2005 | alt.chiApril 2-7 | Portland, Oregon, USA 2165


Nov 5, 2017
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