An Automatic Generation System of Hip Roof Building and Case Study

Prof. Wang Bowei

College of Architecture and Urban Planning, Tongji University, Shanghai, China

Zhang Leyan, Master

College of Architecture and Urban Planning, Tongji University, Shanghai, China

e-mail: zhangleyan1979@hotmail.com

Abstract

This research is our first trial in the field of generative design.

When we do research on the form of building roof, we find the ridge roof is quiet familiar to us not only in China but also other countries. We often meet some architecture design projects that need us to design buildings with the form of ridge roof in consideration of context, function and so on.

Hence we begin to focus on an Automatic Generation System of Hip Roof Building and aim to explore the practicability of using generative design methodology in the field of Architecture and Urban Planning Design.

In this paper, we state the process of automatic generating Three-D models of hip roof building. On the basis of case study, we point out the peculiarity and limitations that exist in the Automatic Generation System of Hip Roof Building at current study stage. At the same time, we make an outlook about the development of this system.

1. Introduction

With the development of computer technology, we have changed our life and culture concept imperceptibly. Nowadays, in the field of Architecture and Urban Planning Design, there are many new design methodology and concept which closely relate to the computer technology have been coming into being, such as dynamic architecture, evolutionary architecture, hypersurface architecture, cyberspace, generative design and so on. Many people, such as Marcos Novak, feel that we are in the centre of a global, architectural renaissance: that we are in an exhilarating climate where the most advanced and challenging architecture being designed around the world could not have been conceived without the use of computer. It is hard to deny such a proposition when looking at the changes in our surrounding. [1]

Nowadays computer technology used in architecture is restricted to drafting, or building up Three-D model after we have designed the architecture. As Frank Gehry once said that computers cannot create the curves of a design, and are only a tool to help us draw the curves as they are in our mind. [2] This is a good explaining what the role of computer is at present. This approach to the computer as an extension of previous design techniques severely limits its potential. [3]

There’s no doubt that computer technology has changed us enormously. So it’s time for us to do some fresh attempt in the field of Architecture and Urban Planning Design, and we want to use generative design method as our first trial. At first, we felt quite puzzle about what kind of research we could do. We thought that Architecture and Urban Planning design were practical science, and decided to put this research on the basis of practicability. We considered that every building or urban planning located in different area, and had different function to satisfy people; but the lack of specific function is totally in keeping with the liquid variability of algorithmic space. [4] Therefore, the morph of building that generated by computer will be quite pseudo. Then we determined to focus on house roof. We find that not only in ancient China but also other foreign nations, there exist many buildings that have ridge roof characteristic. (figure 1) Nowadays, we also design ridge roof buildings in considering of context or function and so on. Hence we chose to do research on an Automatic Generation System of Hip Roof Building, and we found it’s quite useful to generate this kind of roof by generative design method according to its mathematical regulation.

We decide to use this system at the initial stage of our Architecture and Urban Planning design, for we don’t think much about the function of the architecture at this stage, and thus we can make full use of the randomness of computer program to automatic generate much more possibility of one project in a short period of time. This Automatic Generation System of Hip Roof Building is premised on the outline of the architecture’s plane, and it can automatic generate Three-D model of architecture or architecture cluster by using some kind of algorism and programming language such as VC++ and so on. We also set up parameters to control the result of the system. At the first stage of our research, we think that the ridge roof of modern architecture is quite concise in construction than that in ancient China, so we simplify the hip roof, and consider that it is composed of four planar. Furthermore, we make some constraint on the original plane of the building, such as the monomer architecture should be orthogonal and its location in the master plan should also be orthogonal.

2. Method

2.1 Description of the system

We mainly use Visual C++6.0 to edit this Automatic Generation System of Hip Roof Building. Additionally the system comes down to AutoLISP, MAXScipt language what are the script language of Autocad and 3DMAX. Simultaneously, the OpenGL that provides standard program interface is also necessary.

The structure of this Automatic Generation System of Hip Roof Building is composed of category and syntagm. The category class is shown in figure 2.

2.2 Generative process

We take one single building as an example.

2.2.1 Read primitive DXF document

We’ll import primary file what serves as the source of automatic generative Three-D architecture model to the Automatic Generation System of Hip Roof Building in this step.

First of all, we need to set up the primitive file. We shall extract the outline of the building which we want to generate it’s hip roof from the master plan that we have drawn in AutoCAD2000, and save it as the format of DXF document. In respect that it’s our first step in the research and it’s quite reasonable to bring down the difficulty degree for the second step, we determine that the single building’s outline should be orthogonal and it’s position in the master plan should also be orthogonal because of the specialty that most of the hip roof building’s plane are orthogonal. If the position of the architecture cluster is not in orthogonal, we can deal with the buildings placed in the same angle as one group, and rotate them to the orthogonal position, then save them as the format of DXF.

We use the AutoCAD script language AutoLISP to read DXF file into the Automatic Generation System of Hip Roof Building. The outline of the building’s plane will be shown in the view window as figure 3.

2.2.2 Subdivide two-dimensional plane

This operation procedure will divide the building’s plane into several rectangles for the purpose of the next step. We subdivide two-dimensional plane by means of upright (shift vertical line from left to right) and lateral (shift horizontal line from below to above) division according to our algorism.

For example, in the case of subdivision polygon abcdefghij shown in figure 4, we first shift vertical line from left to right. When the line meet the first end point c, according to the algorism, the system will carry out “adding edge” operation, and add an edge names ck. Thus the abck forms a rectangle. The system will exclude the rectangle abck in the next subdivision step, and it’ll carry out “subtract edge” operation at the same time. The edge ab, bc, ak will be subtracted. The same method will be carried out on the polygon cdefghijk until it is subdivided into several rectangles.

In this step, we establish an upright division rate in consideration of the hobby of the user. The total of upright division and lateral division rate is 1. If the parameter is over 0.5, the upright division rate will larger than the lateral division rate. In addition, experiments passing by many times, we discovered that the accuracy of the document in AutoCAD2000 was larger than that in VC++. Therefore it appeared sometimes that when the document of DXF read into the system, the polygon shown in the view window was not close, and thus the subdivision would make some mistake. Therefore, we established in addition another parameter named “accuracy (number after decimal point)” shown in figure 5 for the purpose of avoiding false phenomenon caused by accuracy problem.

The results of the two-dimensional subdivision are shown in figure 6.

2.2.3 Three-dimensional generation

We plan to use this system at the beginning of our Architecture and Urban Planning design and hope to offer designers with inspiration. As we all known, designers often have no accurate request for the image and function of the building at this stage, therefore we give our system much randomness. And we’ll find the results of the generation are quite different from each other.

On the basis of step two, in this step the system will first automatic generate Three-D model of the building with random according to the two parameters “layer number” and “story height (meter) ” established by us, and then generate hip roof on the block that have the same height.

We have set up several parameters such as “height scope of the roof (meter)”, “scope of the roof angel (degree) ”, “probability of center ridge roof ” and “probability of simple sloping” (figure 7) to general control the roof generated by the system.

When the roof angleαequals 90 degree, the system will automatic generate ridge roof with two slope; when roof angle αand roof height h at a certain setting, the four oblique ridges will cross at one point, and the center ridge will inexistent; and when the probability of center ridge is 0, and the probability of simple sloping is 1, the system will automatic generate simple sloping roof building. We look these kinds of roof building as particular cases of hip roof building. (figure 8)

We choose result 2 and result 6 shown in figure 6 as example to generate Three-D models. Because the system can generate lots of models quite different from each other according to the parameters we have set, we select only six results for each time we set up the parameters. The results are shown in figure 9.

There’re several display mode for the Three-D model, such as vertex, wire frame and face. (figure 10) In addition, we can adjust the background colour and the colour of the light. Rest operation contain animation, 360 degree rotation and scaling adjustment in axis x, y, z.

2.2.4 Save automatic generation result

The above three step has finished the procedure of automatic generate Three-D model of hip roof building. Because it’ll cost much manpower to edit more operations function in this system, we decide to use software 3DMAX that has strong function in operating Three-D models. Subsequently, we make use of MAXScript, the script language of 3DMAX as interface and save the format of Three-D model generated by the system as MS document. We found it’s feasible to run the MS document in software 3DMAX5.0. (figure 11, figure 12, figure 13)

3. Application

At the initial stage of our research, we choose architecture design project which master plan conception is quite fit for the requisition of the Automatic Generation System of Hip Roof Building. This architecture design project is a business occupation technical college that locates in Zhejiang province. We are request to design the campus building with ridge roof in accordance with the context in this region. After we have sketched out the planning of the campus, we extract the outline of the main building such as teaching building and so on, and make use of this Automatic Generation System of Hip Roof Building. It’s quite exhilarant that the system generates lots of Three-D models in a short period of time along with the parameters we change each time. From so many results, we get intuitive impression about the campus, and we are enlightened on the spatial morph of the campus or the roof style of the building. Here we select two results that generated by the system shown in figure 14

4. Peculiarity, limitations and outlook

After a series of architecture design projects practice, we find the biggest advantage of this Automatic Generation System of Hip Roof Building is rapid, and it can automatic generate lots of possibilities for the same architecture design project. It’s absolutely impossible for us to design so many possibilities in such short period of time. Moreover, we’ll inspire and get great benefit from the models that generated by the system. There exists greater randomness not only in two-dimensional subdivision but also in Three-D model generation. As a result, we position the usage of this system on the very beginning of Architecture and Urban Planning design, so that designers can get inspiration from the system.

The research of this Automatic Generation System of Hip Roof Building is only at the first stage, and the limitation is also quite obvious. First of all, there exists limitation in the primitive building plane. The system can only handle building which plane and location in master plan is orthogonal. Therefore the system can’t handle if the building plane doesn’t match this term. When the position of the building plane isn’t orthogonal, we should first rotate it to the orthogonal position. However after the Three-D model has been generated by the system, we have to rotate it to the original position when we continue operation in 3DMAX. Thus it increases our workload. In addition, the system can’t handle building plane that is subdivided by us beforehand because of the primitive term that the plane should be outline of the building we have given to the system. Secondly, there exists some unreasonable phenomenon about the Three-D model generated by the system because of the randomness. In this system, we adopt to select two-dimensional subdivision results artificially, and then let the system automatic generate Three-D model. We haven’t given the system opportunity to select and exclude some unreasonable phenomenon by itself. In addition, the generation result is unpredictable, and people can’t precisely control the form of the Three-D model automatic generated by the system. Therefore currently in accordance with the firstly fixed position, this system can only used at the beginning of Architecture and Urban Planning design.

We believe that part of the limitation we have stated above will be improved along with our going further into the research. For example, we can edit other algorithm through which the system can judge building plane which position in the master plan is not orthogonal. Hence we needn’t rotate building plane artificially. This improvement can raise efficiency largely. As to the building plane which is subdivided beforehand, we can also realize its’ automatic generation Three-D model with the improvement of the system.

The much larger development prospect of this Automatic Generation System of Hip Roof Building is the form of roof. Currently, the hip roof model generated by the system is quite simplified. However, there’re many special roof form not only in China but also other foreign countries. (figure 15) Even similar ridge roof, it’s quite different from each other because of the weather, custom and so on. Usually, we can find some parameters that represent the characteristic of the roof form. As long as we summarize these kinds of parameters, write them into the system through programming language, the system can automatically generate lots of Three-D building models which roof have the characteristic of local style.

5.Conclusion

The Automatic Generation System of Hip Roof Building is our first research in the field of generative design. Many experiments we have carried out prove that it’s quite useful to make attempt with some programming language that are quite different from the drafting software we usually use in the field of Architecture and Urban Planning Design. We’ll also find the new methodology can expand our design realm and stir up our creative consciousness.

As we all known, Architecture and Urban Planning design are creation work, and no matter when they can’t get away from mankind. Therefore our architects should have gimlet eye to sense the pulse of the times. Trace back to several years before, architects have to apply paper, pen to draw the building design diagram, and no person can anticipate that we drafting with computer software now. The fast improvement of computer technique has aroused fierce affection in our profession. Therefore, it’s inadequate for us architects to use some software only. We should carry out much more deep thinking, such as what kind of fresh dynamic can computer technology give us in the field of Architecture and Urban Planning Design? We need to communicate with other experts who are learned in computer technology and continue to learn new computer technology at the same time. We should also study new methodology on making use of computer technology in the field of Architecture and Urban Planning Design and proceed with innovation in our design field. We believe that we’ll get much more harvest along with our further study in generative design.

References

[1] Maggie Toy: Editorial, Architectural Design Profile No 136, Architects In Cyberspace Ⅱ, P.7

[2] 刘育东，《数码建筑》，大连理工大学出版社，2002.7，P.068

[3] John Frazer And Manit Pastogi: The New Canvas, Architectural Design Profile No 136, Architects In Cyberspace Ⅱ, P.9

[4] Marcos Novak, Next Babylon, Soft Babylon (trans) Architecture is an Algorithm to Play in, Architectural Design Profile No 136, Architects In Cyberspace Ⅱ, P.23