Copyright Protection Watermarking Algorithms For BIM Model

BIM(Building Information Modeling)is one of digital technology to establish a virtual three-dimensional model of Building engineering,and can provide a complete building engineering information database.In recent years,the continuous deepening and expansion of the BIM technology application has triggered a second revolution in the field of architecture technology,which has developed the application field of three-dimensional GIS and guide GIS from the macro field to the micro field.BIM data contains accurate geometry and relevant data to support the design,procurement,manufacturing and construction activities.It works more accurately and efficiently than traditional processes,and plays an important role in improving production efficiency,saving costs and shortening construction periods.In the digital and networked environment,illegal copying and distribution of BIM models decrease the interests of the owners.BIM model data is a special digital product.How to protect the copyright of BIM model data scientifically and effectively is a difficult problem to be solved urgently in this field.In the past few decades,digital watermarking technology has been regarded as a forward-looking solution for copyright protection of digital products.Digital watermarking as information hiding technology may detect or extract product copyright by imbedding some meaningful or meaningless special watermarking information into the carrier data permanently.The digital watermarking technology can be used for many purposes,such as copyright protection,data integrity authentication,illegal copy protection and so on.At present,digital watermarking technology has been widely used in copyright protection of images,audio,video and text,and has also been preliminarily applied in copyright protection of 3D models.However,there are few reports on copyright protection of BIM model data.Hence,based on the characteristics of BIM model data,the digital watermarking algorithm for BIM copyright protection was studied in this paper.The main work and highlights are as follows:(1)A digital watermarking algorithm for BIM model data considering feature points is proposed.In this algorithm,the coordinates of each vertex of the multi-faceted grid in the original data was gotten from the file and obtains the high-level part of the coordinate data;the one-way function is used to mapping the corresponding relation between coordinate value and watermark bit.The watermark was embedded into the lower effective part of the coordinate by quantitative modulation method,then save the BIM model data with watermark.This is a blind watermark algorithm,so,there is no the original data participation in the watermark extraction procedure.In practical application,because there are many identical values of vertex coordinates in BIM model,there are few effective carrier data can be used for embedding watermark.To solve this problem,random noise is added to the original coordinate data under the error tolerance to embed the watermarks,which indirectly increases the watermark embedding capacity.The data error caused by watermark embedding can be control easily in this algorithm,the use of data is not affected at all.The algorithm is robust against translation,pruning and other attacks,and has certain practicability for copyright protection of BIM model.(2)A robust watermarking algorithm of BIM model data using DFT is proposed.Taking the multi-faceted grid elements in the original BIM model data as the unit,this algorithm extracts all grid vertices of the multi-faceted grid object to construct complex sequence,and makes DFT transformation of the complex sequence to obtain amplitude coefficient and phase coefficient;The watermark information obtained by Logistic mapping scrambling was embedded into the amplitude coefficient of DFT frequency domain by using QIM method.Finally,IDFT transformation is applied to obtain BIM model data with watermark information.This algorithm can well control the data error caused by the watermark embedding,the effect of embedded watermark on the accuracy of BIM model data is small.In addition,it has good robustness against special attacks commonly seen in BIM model data such as cropping,rotation,translation attack and mirroring,which can effectively protect the copyright of BIM 3D model owners.