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The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics
Chen, Jun

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS’’, Bangkok, May 23-25, 2001
In the project of the reconstruction of Zhi-Lian Nunnery, all
the data of the real timber-made components of this ancient
building are measured and represented as line and frame
graphs by a computer. By this way, the connection of different
components can be described completely and it even can
determine the connection quality between mortises and tenons
directly from the screen of a computer. No matter the
usefulness of this, it is not a stereo representation and is
un-convenient for observation. In the following section, the
surface model is used to replace 3D frame model based on the
analysis of the latter.
2.1 3D frame model
An instance of this model is shown in fig. 1, which is
generated by AUTOCAD12.0. The computer records the
coordinate values of all the vertexes in the figure and the
relationship table of the lines between two different vertexes.
This model can provide scenograph of arbitrary direction of
view, but it is not suitable to obtain section graph, intersection
graph of two planes, blanking graph and profile graph.
Therefore, this model can not satisfy the pre-requisite of stereo
modeling completely.
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Figure 1 frame model of timber component
(setvar "osmode" 1) ;endpoint
(initget 1) (setq startPt );getpoint
(if (eq (type pt) 'LIST) (grdraw pO pt -1 1) )))
2.2 surface model
This model firstly uses the sealing parts encapsulated by
edges of different components to define the surfaces of an
object, then defines the object composed by the surfaces. The
data structure of this model is to append an extra information
table to the structure of 3D frame model. It can be used to
process blanking graph, profile graph and so forth. The
following little program is developed under AUTOCAN 12.0 to
compose a surface based on arbitrarily many vertexes:
(defun c:plface (/ r1 t1 ss startPt)
(savenv) ¡saving currently state
(setvar "osmode” 512)
(initget 1)
(setq t1 (getpoint "Select PLINE: "))
((eq (type t1) ’LIST) (setq ss (getpl t1))
(cond ((null ss) (princ “ No Polyline found."))
((= (sslength ss) 0) (princ " Entity is not a Polyline.“))
(if (eq (type pt) 'LIST)
(progn (setvar “osmode“ 0)
(command pt)
(setq n (1+ n)))
(setq loop nil)))
(command '"')
(setq i 1)(repeat n
(command i)
(setq i (1+ i)))
(command ““ "“)
(resenv)) Drenew fore state
A series of surfaces composed by the above program is
shown in fig.2 (after blanking). These surfaces are easy to
observe and can intuitively describe the relationship of
components. This model is the foundation of lignification.