The use of Mixed Reality in architecture for conceptual design J.J. Postema University of Twente, Faculty of EEMC j.j.postema @ student.utwente.nl ABSTRACT

HMD there will only be a table and a chair.

This article describes the use of Mixed Reality in architecture for conceptual design. When an architect virtually creates his conceptual design and is able to walk directly through it for examination with a so called head-mounted display (HMD) and he can use both virtual and real objects in this environment we call this: conceptual designing in Mixed Reality (MR). This paper lists MR systems (and their functionalities) that are and could be used for the conceptual design process in the architecture. This paper further gives the added value of Mixed Reality on the design process.

Keywords Mixed Reality, Augmented Reality, Virtual Reality, conceptual design, architecture.

Figure 1. Table and chair in a virtual environment

1. INTRODUCTION

The purpose of this research is to get a better understanding of the use of Mixed Reality, which could be (or is already) applied in the field of conceptual design in the architecture.

3D computer-aided design (CAD) is mostly used in the modern architecture. This software makes it possible for an architect to create and evaluate conceptual designs (e.g. buildings). On the computer the architect can rotate, zoom in on and change the cameras viewpoint of the conceptual design. The newest 3D CAD programs work geometrically almost perfect. But there are imperfections that cannot be noticed by the architect on the computer screen. A method to verify if a building is constructed in a realistic way is to place virtual objects like tables, couches, trees or human beings in the conceptual design. This method gives the architect an impression of the spatial dimensions in reality. However this ‘trick’ only happens on the computer screen. The architect would get a much better impression when he can walk directly through (or in) his conceptual design and place objects from the real (or virtual) world. When an architect virtually creates his conceptual design and is able to walk directly through it for examination with a so called head-mounted display (HMD) and he can use both virtual and real objects in this environment then we call this: conceptual designing in Mixed Reality (MR). Figure 1 [AEI03] for example, is a picture of the real world augmented with virtual reality. The architect can create a conceptual design and he can directly walk around it. Without a Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission. 2nd Twente Student Conference on IT, Enschede 21 January, 2005 Copyright 2005, University of Twente, Faculty of Electrical Engineering, Mathematics and Computer Science

This article gives the answers to the following research questions: Which Mixed Reality systems are and could be used for the conceptual design process in the architecture? What are the functionalities of these Mixed Reality systems? What value does Mixed Reality add to the design process? The types of results to be delivered are answers to the research questions and are analyses of researches on Mixed Reality that are relevant to the conceptual design for architecture. Therefore this article shows several Mixed Reality applications with their functionalities and gives their added values to the design process in the field of architecture. The structure of this article will be (section 2) background information, (3) an introduction to Mixed Reality and conceptual design [OT99] [Azu01], (4) Mixed Reality in relationship with conceptual designing for architecture [AEI03] [Kal93], (5) the functionalities of an existing Mixed Reality application for conceptual design and their added value to the design process, (6) the functionalities of potential applications for conceptual design and their added values, (7) an overview of the answers on the research questions (8), at last the conclusions and future research.

2. BACKGROUND INFORMATION Descriptions and analyses of Mixed Reality applications that are especially designed for architecture or that could be interesting for architectural designs are used for this research. There is a lot of relevant research in Mixed Reality and conceptual designing, like techniques that provide users with a natural, tangible interface for selectively zooming in and out of specific areas of interest in an Augmented Reality scene [LBC04].

And there are techniques where the virtual “environment provides a means of creating and manipulating basic geometry, using a kiosk toolbox” [Figure 1] [AEI03, 59]. Also there was a group of scientists that created a design system which supports the reality-virtuality continuum for Architectural Engineering and Construction (AEC), by enhancing the real environment with fixed and mobile augmented reality [DCG03]. Mixed Reality is also used in the field of evaluating automobile interior design [OKY03]. Because of increased computer power and latest technologies Mixed Reality is a dynamic field. Before Mixed Reality is put into practice there must be a good overview of existing Mixed Reality applications that are and could be used for the architecture. That makes this research very interesting for the modern architecture. Despite of the fact that there are not much empirical studies [TOB03] of AR effectiveness, the article brings to light the relevance of the relationship between Mixed Reality and conceptual design in the architecture.

3. MIXED REALITY AND CONCEPTUAL DESIGN This topic will briefly introduce what Mixed Reality and conceptual design is. It will be brief because it is not the main purpose of this research to explore what the functionalities of MR are. The scope is narrower than MR namely the use of MR in architecture for conceptual design. However it is useful for the reader to give a justification of the terminology that is used in this article and to explain a little bit about the physical environment of typical Mixed Reality systems.

3.1 Justification terminology The term Augmented Reality (AR) (i.e. the real world augmented with data from the virtual world) was first used in combination with Mixed Reality [MK94]. Azuma redefined AR as a system that (1) combines real and virtual, (2) is interactive in real time, and (3) is registered in three dimensions [Azu97]. A newer proposal is that the continuum of MR contains AR and Augmented Virtuality (AV) [OT99] (i.e. virtual reality augmented with data from the real world). In this paper conceptual design in Mixed Reality means conceptual design in the whole spectrum of Mixed Reality in three dimensions. It is Mixed Reality and not Augmented Reality because in the case of architecture in conceptual design, virtual and real environments can flow into each other. Sometimes there will be many virtual objects and sometimes a few. This in accordance with the important conclusion of Milgram: ‘Determining whether an image should be considered Augmented Reality or Augmented Virtuality is not necessarily a matter of simply summating the respective areas of real and virtual images in order to determine a majority portion of real or virtual’ [OT99, 12].

3.2 Mixed Reality display techniques Display devices for mixed reality are most easily categorized as head mounted (Figure 2 [SCH04]) and non-head mounted devices. Especially head mounted displays will be used in the architecture because non-head mounted displays are limited in their usefulness by their limited working volume and by potential space constraints. [OT99, 37]

Figure 2. HMD for Mixed Reality View “Two kinds of head mounted displays have been used: optical see-through and video see-through. Optical see-through systems combine the real and synthetic imagery via some optical merging mechanism […] Video see-through systems combines synthetic images with real images of the user’s surroundings by combined two video streams.” [OT99, 32]

3.3 Conceptual design Traditionally the conceptual design in the architecture was based on paper drawings. In the 17th Century, “the architect Wotton (1624) argued that no one should build on the basis of a paper drawing such as a plan or a perspective, but rather they should see a model of the whole structure at as large a scale as possible. In more recent times, the use of 3D models to support collaborative design work, rather than simply presentation of the final design, has been prompted by a desire to increase public participation.” [Why02, 38] This is the thought behind computer-aided design (CAD). CAD software is used by architects, engineers, drafters, artists, and others to create precision drawings or technical illustrations. CAD software can be used to create two-dimensional (2D) drawings or three-dimensional (3D) models [WHA04]. In the architecture CAD programs are often used.

4. WHY USE MIXED REALITY FOR CONCEPTUAL DESIGN? In this section I will try to answer the following question: is mixed reality interesting in architecture for conceptual design? This is necessary to know because the research questions almost imply a positive answer to the above question. As mentioned in the introduction: “the architect would get a much better impression when he can walk directly through (or in) his conceptual design and place objects from the real (or virtual) world. When an architect virtually creates his conceptual design and is able to walk directly through it for examination with a so called head-mounted display (HMD) and he can use both virtual and real objects in this environment then we call this: conceptual designing in Mixed Reality (MR).” But is there any scientific research done for the added-value of Mixed Reality in architecture for conceptual design? A lot of research is done in the field of Mixed Reality and there is also a lot to find about CAD. But that is not the main subject of this article. At the end of 2004 there are only a few empirical studies concerning the effectiveness of Mixed Reality [TOB03]. As a result there is almost nothing to find about the effectiveness of Mixed Reality in architecture for conceptual design. More scientific research in this field is a recommendation. However there are a lot of applications that make use of Mixed Reality and that could be useful for architecture. This will be discussed in section 8.

Anderson, Esser and Interrante [AEI03] plead that mixed reality can fill the gap for the limited acceptance of CAD in the area of conceptual design in architecture. They write that CAD has had limited acceptance in the area of conceptual design in architecture, but has been of great benefit in all other areas of design. There are several reasons for this: (1) The limited viewing angle and limited resolution of a typical computer screen leads to a tendency to concentrate on external form rather than inhabitable space; (2) “The design of the space can be negatively influenced by the shape of the screen and by its strong horizontal and vertical edges.” [AEI03, 56]; (3) CAD applications are optimized for the creation and manipulation of geometry rather than the manipulation of imagery and spatial creation; (4) The objects being created are mostly from a static viewing position and sensed only in a limited visual manner. Many of these problems could be overcome with an MR design environment. “Care must be taken, however, so that the designer is not just placed ‘on the other side of the screen’ in an environment that, though it may be suitable for creating geometry, does not otherwise support the design process.” [AEI03, 56] The gap between real and virtual in the architecture is not new. A group of researchers come to the following conclusion: “Augmented reality is bridging the gap between the physical and the digital environments and by nature it only exists through the constellations of objects both physical and digital. Augmented reality can be seen as a sort of atmosphere, a category, which is possible to conceptualise and design and thereafter decide what objects should be part of the concept to fulfil the design intentions.” [Kro00, 136] So the answer to the question ‘is mixed reality interesting in architecture for conceptual design?’ is: yes, it bridges the gap between virtual and real worlds in the architecture.

5. AN EXISTING MIXED REALITY APPLICATION FOR CONCEPTUAL DESIGN An important Mixed Reality system for the conceptual design in architecture is developed at the University of Minnesota by Lee Anderson, James Esser and Victoria Interrante. The System “provides a means of creating and manipulating basic geometry using a kiosk toolbox […] for using imagery and videos developed outside of the environment for use within the environment for both information and design. A DesignStation is provided within the environment to create a work area for the designer, concentrating imagery and information associated with the design as well as an area for reflecting upon, presenting and critiquing the design process” [AEI03, 57].

5.1 Functionalities of the application The system is able to perform every task of normal 3D CAD programs, like creating, manipulating, copying and deleting rectangular solids and cylinders. The virtual design environment provides a environment for images, both still and moving, as well as 3D geometry. Pictures, textures and videos intended for use within the virtual environment are dropped into a folder. They can be accessed within the virtual environment by selecting them from a rotating drum on the toolbox kiosk. Both purely virtual components and real components are represented in the virtual world. Allowing for the representation of real components in the virtual world enables the architect to incorporate environment objects such as stools and chairs that

can make inhabiting the virtual space more comfortable and thus permits more sustained attention. Real objects can also provide physical aids, such as a worktable, that a designer can rest arms and hands upon. To support presentation and critique of a design while in process the environment provides the ability to take "snapshots" and "videos" of important aspects of a design as seen through the HMD. The images/videos are saved and added to other images on the DesignStation surfaces. The system supports simultaneous multiscale viewing so that conceptual models can be designed and observed at any scale, typically ranging from the scale of an architectural model – a foot or two across – up to actual size. “Simultaneous multiple scales are supported so that a project can be designed, for example, at a relatively small scale while simultaneously being inhabited or observed at full scale, or visa versa, with modifications made to the model at one scale appearing simultaneously at the other.” [AEI03, 61]

5.2 What is the added value of the application for conceptual design? As mentioned before the system is (1) bridging the gap between the physical and the digital environment that exists when working with 3D CAD software. The real object in the virtual world makes it possible for the architect to support (2) fine motor movement such as that required when working on designs at a small scale. By making at least some of the commonly encountered objects in the virtual space physically present, (3) the quality of the architect’s experience of the space improves. (4) Another added value compared to traditional architecture is easier support of presentation and critique of a design while in process, by making snapshots. There are several added values of the virtual design environment that provides an environment for images, both still and moving, as well as 3D geometry. The following paragraph lists added values to the MR system when making use of images: “5.1) to provide detailed information and reference within the DesignStation; 5.2) to establish a larger contextual environment; 5.3) to represent real objects, such as people, for scale and indication of activity; 5.4) as a substitute for geometric objects; 5.5) for surface representations such as plans and facades; 5.6) for use as DesignStation "skins"; and 5.7) for symbolic representation of intention, where the symbolic ideas that can be expressed in a graphic are more appropriate for conceptual design than a geometric object.” [AEI03, 59] Although the above given added values are plausible added values they are not scientifically or empirically grounded. These are arguments that come from the developers of the system. The 7 topics under the 5th added value are not facts but logical thoughts.

6. POTENTIAL MIXED REALITY APPLICATIONS FOR CONCEPTUAL DESIGN Useful Mixed Reality applications must be able to support the normal 3D CAD tasks. This paper will focus on three recent developments in Mixed Reality: a Mixed Reality system with visual and tangible interaction capability [OKY03]; a system called A4D which gives intuitive information presentation provided by tangible mixed reality user interaction, in indoor settings [DCG03]; and zooming in and out in a Mixed Reality environment with 3D MagicLenses [LBC04].

The first two systems implement normal 3D CAD tasks. Literature about the 3D MagicLenses does not mention CAD explicitly; however a house demonstration gives the advantages of this technique for conceptual design, the technique is flexible and could be usable for existing 3D CAD.

6.1 Functionalities of the applications 6.1.1 The tangible Mixed Reality system The first Mixed Reality system that will be discussed and that could be useful for conceptual design does not have a name. The creators describe it as follows: “In this configuration, the

Figure 4. Tangible interface

virtual object for observation and the physical object for tangibility are completely registered in the space. Thus they can be identified as one object and give natural interface in visual and tangible manners.” [OKY03, 1]

A4D is capable to do selecting operations on virtual objects. With the pen in the mixed reality environment A4D can scale and perform operations on the virtual object.

This application was tested for evaluating automobile interior design. The researchers propose (without scientific argumentation) that “in order to give a high level of reality in a MR space tangibly and visually at the same time, the following two points are particularly critical: hand visualization and accurate registration.” [OKY03, 1] The whole idea behind this system is that the user can see his real hands and touch the objects with a virtual image layer on it. On the left in Figure 3 [OKY03] a real image is shown of a

hand on the automobile switches. In the MR space, as shown on the right in Figure 3, the user can see his real hand on the virtual device.

The system is able to identify the pattern inscribed in the marker and view the associated 3D object logically linked to it, in real time, as soon as the video camera views that marker. A4D has a marker on the cube for the world reference frame, which is logically and synchronously linked to the 4D model viewed in the A4D editor desktop and four function markers to associate editing functions in augmented reality: select and deselect objects, scale, rotate and translate. The system also supports multi-user interactive 4D information visualisation and design of construction spaces. A4D is especially designed for general architecture. This makes it possible to use the system for conceptual design in the architecture. The system has the ability to do geometrical and topological checks on the shape of objects. The system can take several 3D designed layers of a construction project: architectural, structural, water and sewage, etc., integrate them together and check for possible geometrical and geometrical inconsistencies among them.

6.1.3 3D MagicLenses Figure 3. Real image; and MR image Although it is not an MR application that is purely written with an architectural background, the producers use virtual objects from CAD data. This makes it useful for conceptual design in the architecture.

6.1.2 A4D Researchers created a design system which supports the MR continuum for Architectural Engineering and Construction (AEC), by enhancing the real environment with fixed and mobile augmented reality. This design is called A4D. [DCG03] A4D's research area is the interface between design and construction planning processes. The construction planning process is not relevant for this article, but the design process interface that makes use of MR could be serviceable for conceptual design in the architecture. “A4D enables the user to view and perform simple interaction tasks within an augmented reality environment. A4D provides tangible user interaction […] A4D is applicable for the enhancement of physical scale models in the Architectural Conceptual Design process.” [DCG03, 10] A4D has a wireless tangible interface (Figure 4 [DCG03]). The interface has physical cubes with different markers attached in each side, with the exception of one side, which has a pen.

3D MagicLenses techniques involve 3D lenses, information filtering and semantic zooming. “These techniques provide users with a natural, tangible interface for selectively zooming in and out of specific areas of interest in an Augmented Reality scene.” [LBC04, 1] They use quick and fluent animation to help users integrate the relationship between views of detailed focus and global context. There are 3 main functionalities: (1) Examining distant objects closer and examining close objects in greater detail. (2) Selecting and manipulating virtual objects in MR view. (3) Filtering the information shown in the AR and VR views, either by selectively hiding content, or adjusting its representation. The last functionality is the most powerful one in MR for conceptual design in the architecture. Various components of a virtual house model can be enabled or disabled through the lens. For example (see the right picture in Figure 5), all parts of the house other than the internal wooden framing can be turned off so that through the lens the user sees the frame while outside the lens the complete house remains.

computer screen. With Mixed Reality the architects ‘feel’ the environment rather than observing it.

7. AN OVERVIEW OF THE ANSWERS There is much more to say about other Mixed Reality systems that are useful for the architecture. However the systems that are chosen for this research are not just four randomly chosen systems, they are a result of a long search in the field of Mixed Reality and Architecture. This section gives an overview of the answers on the research questions. Figure 5. Two users examining; and a view with the lens

6.2 What is the added value of the applications for conceptual design? 6.2.1 The tangible Mixed Reality system Because the user can see his own hands and can actually feel the objects by touching them with his hand, “the sense of distance to the surrounding virtual world and the sense of scale are improved, becoming more direct than when only the visual sense is available”. The researches found that users “enhanced the feeling of reality and actually being there.” [OKY03, 2]

6.2.2 A4D The “level of integration: multi-user 4D virtual environment and simulation, wearable systems, novel augmented reality interaction, construction project schedule technologies, turns A4D into a highly innovative system.” [DCG03, 12] The authors are right when they call the system highly innovative. But in the whole article not much is written about the added value for the design process. The ‘why?’ behind the development of this innovative system is never answered. That MR bridges the gap between virtual and real worlds is never even mentioned. It is a lack in the article that there is no empirical proof or even a suggesting to the ‘why’ behind the use of the system for conceptual design in the architecture. It looks like the researchers are very enthusiastic about the system and that is the reason that architects must use it. A possible added value (with respect to traditional architecture but also to other MR systems) of the A4D system is the ability to check for possible geometric errors. So it automatically recognizes errors that architects accidentally make. However this is a functionality that is taken over from traditional 3D CAD functionalities. The creators based it upon the OpenCascade toolkit. This is a well-known general toolkit for 3D CAD applications that features topological and geometrical checks on the shape of objects. [OPE04] A possible ‘added value’ is that it gives users confidence to know that the MR system A4D is based upon the OpenCascade toolkit.

6.2.3 3D MagicLenses The 3D MagicLenses technology could allow people with varied interests to efficiently collaborate around a design project, such as a house (see the left picture in Figure 5). “The ability to transition into a VR view allows users to explore the environment from a first-person perspective, while still in possession of their lens tool. […] Each user could navigate around the building while still in possession of their lens tool. From this perspective they could examine the interior of the building and still benefit from the information filtering abilities of the lens.” [LBC04, 6] Traditional architecture applications that do not make use of 3D MagicLenses can only look at mockups, blueprints or look at a

Which Mixed Reality systems are and could be used for the conceptual design process in the architecture? The focus in this paper was especially on applications that could make use of CAD functionalities and that have somehow addedvalue to the conceptual design process. Furthermore only systems with a reliable academic background were selected. At this moment there is one MR application that is explicitly made for conceptual design in the architecture. That is the kiosk toolbox developed at the Department of computer science

and architecture at the University of Minnesota in the USA. The first system that could be useful for conceptual design in the architecture is the tangible Mixed Reality system made by

MR Systems Laboratory of Canon and published in the ACM International Symposium on Mixed and Augmented Reality in 2003. The second one is A4D developed at the University of Balearic Islands in Spain. And at last is the 3D MagicLense from the department and laboratory of Computer Science at the University of Canter-

bury in New Zealand. What are the functionalities of these Mixed Reality systems? The functionalities that I give in this conclusion will begin with the functionalities that are most commonly used in 3D CAD programs followed by more specific MR functionalities. These MR systems must be able to perform every task of normal 3D CAD programs, like creating, manipulating, copying and deleting of rectangular solids and cylinders. Most of the virtual design environments provide an environment for images, stationary and sometimes moving, as well as 3D geometry. Multiscale and multiuser viewing is another functionality of the analysed systems. Multiscale viewing is important because the conceptual models can be designed and observed at any scale, typically ranging from the scale of an architectural model - a foot or two across - up to actual size. Simultaneous multiple scales are sometimes used so that a project can be designed, with modifications made to the model at one scale appearing simultaneously at the other. The multiuser mode creates the ability for different users to look at the design in the Mixed Reality environment from their point of view and when necessary on their parts of interests of the virtual objects. Real objects can also provide physical aids, such as a worktable, that a designer can rest arms and hands upon. To support presentation and critique of a design while in process the environment provides the ability to take "snapshots" and "videos" of important aspects of a design as seen through the HMD. The images/videos are saved and added to other images on the DesignStation surfaces. At any time there must be an option to make changes in the conceptual design. So a system that is made for conceptual

design in architecture must not only be in Mixed Reality in a 3D environment but also real-time. A4D is especially designed for general architecture that makes it possible to use the system for conceptual design in the architecture. The system has a feature that checks for geometrical checks on the shape of objects. The system can take several 3D designed layers of a construction project: architectural, structural, water and sewage, etc., integrate them together and check for possible geometrical inconsistencies among them. The filter option of the 3D MagicLenses makes it possible to select, hide or adjust the representation. What value does Mixed Reality add to the design process? The system is bridging the gap between the physical and the digital environment that exists when working with 3D CAD software. The real object in the virtual world makes it possible for the architect to support fine motor movement such as that required when working on designs at a small scale. By making at least some of the commonly encountered objects in the virtual space physically present, the quality of the architects’ experience of the space improves. Easier support for presentation and critique of a design while in process, by making snapshots, is another added value compared to traditional architecture. The representation of real components in the virtual world enables the architect to incorporate environment objects such as stools and chairs that can make inhabiting the virtual space more comfortable and thus permits more sustained attention. Mixed Reality can establish a larger contextual environment. Traditional architecture applications that do not make use of Mixed Reality can only look at mockups, blueprints or look at a computer screen. With Mixed Reality the architects ‘feel’ the environment rather than observing it. The use of MR systems enhance the feeling of reality and actually being there. When an user feels that he is in the world of his conceptual design he can focus on his design rather than on the annoying distance between the real and the virtual world.

So a recommendation would be to conduct more empirical research about the effectiveness of Mixed Reality in the architecture for the conceptual design process. Future research questions could be: what is the long term effectiveness of Mixed Reality in the architecture for the conceptual design process? Does it save time and money in the conceptual design process? And is the added value, as described in this paper, added value for a company? Most of these questions could intuitively be answered positively, but once again that is not scientifically legitimate. Furthermore the existing MR architecture application for conceptual design, the DesignStation with the kiosk toolbox (see section 5), could make use of the functionalities of the other potential MR applications. This can add several values to the design process of the existing MR architecture applications as discussed in section 6.2.

REFERENCES [AEI03] Anderson L., Esser J., Interrante V, A virtual environment for conceptual design in architecture, proceedings of the workshop on virtual environments, 2003, 57-63 [Azu01] Azuma R.T., etc., Recent Advances in Augmented Reality, IEEE computer graphics and applications, November 2001, 34-47 [Azu97] Azuma R.T. A survey of augmented reality, Presence: Teleoperators and Virtual Environments, vol. 6, no.4, 1997, 335-385 [DCG03] Dias J.M.S., Capo A.J., Carreras J., Galli R., and Gamito M. A4D: Augmented Reality 4D System for Architecture and Building Construction, Conference Virginia technologies, 2003 [Kal93] Kalawsky R. S., The science of Virtual Reality and virtual environments, Addison-Wesley, Workingham, 1993, 330-332 [Kro00] Krogh P., Interactive Rooms - augmented reality in an architectural perspective, communications of the ACM, 2000

The Multiuser mode makes it possible for architects to work together in one conceptual design. This is more efficient than an architect working alone.

[LBC04] Looser J., Billinghusrt M., and Cockburn A., Through the Looking Glass: The use of Lenses as an interface tool for Augmented Reality interfaces, communications of the ACM, 2004

One system can take several 3D designed layers of a construction project: architectural, structural, water and sewage, etc., integrate them together and check for possible geometrical and topological inconsistencies among them.

[MK94] Milgram P. and Kishino F., A taxonomy of mixed reality visual displays, IEICE Trans. Inf. & Sys., vol. E77-D, no.12, 1994, 1321- 1329

The added value of the use of OpenCascade in the case of A4D is that it gives users confidence to know that the MR system A4D is based upon the OpenCascade toolkit.

8. CONCLUSIONS AND FUTURE RESEARCH Mixed Reality is a popular topic for researchers, a lot of applications and hardware for Mixed Reality can be found. But there are not much empirical studies of AR/MR effectiveness, especially not for conceptual design in the architecture. Most of the cases have assumptions that it is effective. For example there is no study about the long term effectiveness of Mixed Reality in the design process. Also the bridging of the gap between virtual and real world is true, but is it really necessary for architects to bridge this gap? Or is it something Mixed Reality researchers want to believe because it is a beautiful and exciting development?

[OKY03] Ohshima T., Kuroki T., Yamamoto H., and Tamura H., A Mixed Reality System with Visual and Tangible Interaction Capability, Application to Evaluating Automobile Interior Design, IEEE & ACM ISMAR, 2003 [OPE04] Open CASCADE, creator of the Industrial Open Source project, www.opencascade.com/about, available at 8-12-2004 [OT99]

Ohta Y. and Tamura H., Mixed reality – merging real and virtual worlds, Springer, Berlin, 1999

[SCH04] Schepens Eye Research Institute, Head Mounted Display as a Low vision Aid, http://www.eri.harvard.edu/faculty/peli/projects/headmounted.html, available at 30-11-2004 [TOB03] Tang A., Owen C., Biocca F., and Mou W., Comparative effectiveness of augmented reality in object assembly, communications of the ACM, 2003

[WHA04]Whatis.com, http://www.whatis.com, available at 2911-2004 [Why02]Whyte J., Virtual Reality and the Built Environment, Architectural Press, Oxford, 2002