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The Open Cybernetics & Systemics Journal, 2014, 8, 613-617 613
1874-110X/14 2014 Bentham Open
Open Access
An Improved Ray Casting Algorithm Based on Morphological Segmentation
of Multiple Structure Elements
Huiling Hou*, Mingquan Wang, Xiaopeng Wang and Jinkun Lv
National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan, 030051, China
Abstract: Aim at traditional ray casting algorithm existing the problems that powerful computing capacity and slow ren-
dering velocity, an improved ray casting algorithm is presented in this paper. To reduce the number of voxels in recon-
struction process, the image segmentation is introduced to volume rendering. A segmentation algorithm based on multiple
structure elements is proposed to process ICT slice images original data field. The original voxels are divided into two
parts: the target voxel data set and the background voxel data set. Then, the target voxel data set is constructed as a new
data field, and using the ray casting algorithm to it. This reduces the number of voxels and accelerate the efficiency of ray
casting. The results of reconstruction show that this algorithm can greatly reduce reconstruction volume data and improve
the efficiency of ray casting.
Keywords: ICT, multiple morphological structure elements, ray casting algorithm.
1. INTRODUCTION
Visualization in Scientific Computing (ViSC) is a new
important research direction of computer graphics. The main
idea is converting a large number of engineering test data
which generated by engineering operations into 2D graphics
or 3D images by using the basic principles of computer
graphics [1, 2]. Visualization technology in ICT converts 2D
CT test data into 3D stereo images, which intuitively reveal
workpiece defects. It makes engineering staffs have multi-
angle and multi-level observation. Also, it can enhance the
ability of detection and provide more comprehensive and
precise analysis results to non-destructive testing [3]. There-
fore, visualization technology in ICT has important practical
significance and research value. javascript:void(0);
The ray casting algorithm is the classic algorithm of vol-
ume rendering technology, which has been widely re-
searched and applied. The simple principle and the easy re-
alization are the main advantage of the ray casting algorithm.
It can also keep the details of 3D image, enhance the overall
rendering effect and generate high quality images to display.
But visualization speed still can not satisfy with constantly
improving in industrial imaging device resolution and huge
volume data field. Seeking to speed up the rendering speed,
improve the rendering quality, have become the focus in the
3D visualization technology [4].
Different from the traditional ray casting algorithm, this
paper uses a segmentation algorithm based on multiple mor-
phological structure elements to process ICT slice images
original data field in the image preprocessing stage. The new
algorithm can solve the problems of powerful computing
capacity and slow rendering velocity.
Address correspondence to this author at the National Key Laboratory for
Electronic Measurement Technology, North University of China, Taiyuan,
030051, China; Tel: +86-351-3925298; E-mail: hou_huiling@126.com
2. ALGORITHM DESCRIPTION
2.1. The Ray Casting Algorithm Principle
The general flow of ray-casting algorithm is: data classi-
fication and color assignment -ray tracing and data resam-
pling -image composition. Firstly, a viewing ray casts into
the data set from each pixel on the image plane and intersects
the volume data set. Secondly, along each ray, a number of
sampling points are taken, and the color and opacity at each
re-sampling point are interpolated at the eight surrounding
points in object space. Finally, the color and opacity of the
re-sampling points of each ray are subsequently composited
in depth order to obtain the final color value of the pixel [4,
5]. The schematic diagram is shown in Fig. (1).
The ray casting algorithm can show very rich internal in-
formation. But in order to get better rendering effects, it is
needed that more light projection data and sampling many
times for every light, which have greatly affected rendering
speed. Volume rendering method can't change external light
and perspective flexibly. Each change means that the whole
drawing process needs to start again.
2.2. A Segmentation Algorithm Based On Multiple Mor-
phological Structure Elements
2.2.1. Basic Theory of Mathematical Morphology
Mathematical morphology is developed from set theory
and extended to image analysis by Serra. Based on set the-
ory, mathematical morphology is a very important theory,
whose operation must be defined by set arithmetic. Its basic
idea is to use a certain form of structural elements to meas-
ure and extract the corresponding shape of image in order to
achieve the right image analysis and recognition purposes.
The basic mathematical morphology has four basic morpho-
logical operators: dilation, erosion, opening and closing
operator
[6].