最新刊期
卷 14 ， 期 5 ， 2009
- 摘要：The study addressed the emotion measurement in affective computing area, and construed the significance of the discrete emotional categories approach and the dimensional approach. The traditional psychological measurement method was used to collect the rating scores of 330 pictures on 16 emotional dimensions proposed by the previous psychological research. The results showed PAD (Pleasure-Arousal-Dominance)dimensions were sufficient and essential to represent the emotional states. The study further proposed the dimensional approach is based on the quantitative analysis, and it is the main approach to solve the computability of emotions. The model of PAD dimensions is essential to promote the affective computing research.关键词：affective computing;emotion measurement;the dimensional approach;PAD dimensions7456|362|0更新时间：2024-05-07
- 摘要：An important task of affective computing is to build computable emotional models. In our study, PAD theory is used and EBM (emotional block model)is built and verified in facial emotion recognition area. 88 points based Gabor feature and SVM (support vector machine) classifier are used to verify this model on Cohn-Kanade dataset. Non-basic and basic emotions are recognized with EBM model in our experiment, and the advantage and disadvantage are compared with PAD based models and traditional basic emotional models. Experimental results show that EBM is reliable. The result is better in high-convergent emotional block than in low-convergent emotional block.关键词：facial emotion recognition;PAD (pleasure arousal dominance) theory6329|350|0更新时间：2024-05-07
- 摘要：Along with the rapid progress of the technologies in human computer interaction and affective computing, facial expression recognition has been actively researched. To clarify the research direction and development of facial expression recognition in human computer interaction, the research states of facial expression recognition are analyzed from the aspects of facial expression database, facial feature extraction, facial expression classification methods, robust facial expression recognition, fine-graded facial expression recognition, mixed facial expression recognition, and non-basic facial expression recognition. Finally, the study hotspots and trends of facial expression recognition are concluded, the limits in facial expression recognition are pointed out, and the expectation of the development of facial expression recognition is given.关键词：facial expression recognition;emotional facial expression;facial expression database7399|512|0更新时间：2024-05-07
- 摘要：Computational emotion models for virtual humans are very important in many fields. A believable virtual human should have both geometry shape, and autonomous emotion. Based on previous researches on emotion models, a new motivation-driven based autonomous emotion model is set up. A cognitive architecture of virtual human is presented by psychology and neural science; it includes perception, emotion, mood, personality, motivation and behavior. A formalization of inner motivation and external stimuli is built; the intensity of a basic emotion can be calculated in the model, and emotion state is the union of all basic emotions. In order to realize the self-adapting mechanism of emotion, a Q-learning method for emotion learning is also proposed. A 3D virtual scene with virtual humans is realized on PC, new emotion model can make a virtual human’s autonomous emotion expression more believable, the experiment shows that our method is effective in virtual human’s emotion simulation.关键词：virtual human;emotion;motivation5771|298|0更新时间：2024-05-07
- 摘要：Human face morphing is the foundation of facial expression synthesis and talking avatar animation. In this paper, an MPEG-4 based method for human face morphing and expression synthesis is proposed. The method uses a picture of neutral human face and a group of face animation parameters (FAP)as input, and the output is a corresponding facial expression image. There are four stages: facial feature point extraction, mesh generation for specific human face, mesh points movement driven by FAPs, and face texture mapping. After these four stages, photos of various facial expressions are created. Novel algorithms are also implemented for eyeball movement and texture mapping inside the mouth. Perceptual evaluation shows that the face morphing method can synthesize realistic and natural facial expressions for various human face models of different genders, ages and races. Meanwhile, this method is real-time, so it can be used in the areas of video processing and facial animation.关键词：face morphing;facial expression;MPEG-46063|315|0更新时间：2024-05-07
- 摘要：Based on the analysis of the characteristics of different expressions in the human face, it was found that using the same method to extract the facial features cannot maximize the availability of information. The lost of useful information and the redundant computing may reduce the accuracy and the performance the algorithm. Aiming at the three specific parts on the face-mouth, forehead and eyebrows-which makes the largest changes in shape, texture and distance when facial expression changes take place, a new multi-feature extraction method is developed. To extract the features, it applies template matching on the mouth, edge detection on the forehead and contour detection on the eyebrows. The integration of the three feature extraction outputs becomes the final result of the system. Experiments validated the algorithm with stability, effectiveness, a high recognition accuracy and fast running speed.关键词：facial expression recognition;multi-feature extraction;template matching;edge detection5157|298|0更新时间：2024-05-07
- 摘要：In this paper, we utilize the partial least squares regression (PLSR)method to solve the simultaneous recognition problem on face identity and face expression. Firstly, face features and the corresponding semantic features are extracted for each face image as the input features, where the face features are defined as the Gabor wavelet coefficients defined on several land marks of each face image;the geometric features are defined as the coordinates of the landmark points and the semantic features are defined as the facial expression category index and face identity index of each face image. The kernel principal component analysis (KPCA)method is then applied to deal with the feature fusion task of both Gabor features and geometric features. Finally, the PLSR method is used to model the correlation between the input facial feature vectors and the semantic vectors. Based on this model, both face identity and facial expression category of any test facial image can be predicted. Experiments on both JAFFE facial expression database and AR face database show the effectiveness of the proposed method.关键词：partial least squares regression;face recognition;facial expression recognition5145|293|0更新时间：2024-05-07
- 摘要：This is the fourteenth in the survey series of the yearly bibliographies on image engineering in China. The purpose of this survey work is mainly to capture the up-to-date development of image engineering in China, to provide a convenient means of literature searching facility for readers working in related areas, and to supply a useful reference for the editors of journals and potential authors of papers. Considering the wide distribution of related publications in China, 915 references on image engineering research and technique are selected carefully from 3359 research papers published in 120 issues of a set of 15 Chinese journals. These 15 journals are considered as important journals in which papers concerning image engineering have higher quality and are relatively concentrated. Those selected references are classified first into five categories (image processing, image analysis, image understanding, technique application and survey), and then into 23 specialized classes according to their main contents (same as last year). Some analysis and discussions about the statistics made on the results of classifications by journal and by category are also presented. This work shows a general and off-the-shelf picture of the various progresses of image engineering in China in 2008. It should be pointed out particularly that, in 2008 the number of research papers for image engineering, published in the above 15 journals still maintains an increasinge in quantity and reaches a new high stage in the history. A strong tendency of continuing development of image engineering in China is clearly visible.关键词：image engineering;image processing;image analysis;image understanding;technique application;literature survey;literature statistics;literature classification4612|432|0更新时间：2024-05-07
- 摘要：Estimating the information of electric activity source within the brain from the potential distribution measured on the scalp is called EEG (electroencephalographic) inverse problem. In this paper，a new method based on state space model is proposed. The proposed strategy formulates the source activity distribution through kinetics of brain neurons，and the potential distribution measured on the scalp through observation equations，thus makes it possible to unify the dynamic reconstruction problem and static reconstruction problem into a general framework. Further，it coherently treats the uncertainties of the statistical model of the imaging system and the noisy nature of measurement data. The performance of the proposed framework is evaluated using simulated phantom data and real EEG data with favorable results.关键词：EEG;inverse problem;state-space;Kalman filter4162|257|0更新时间：2024-05-07
- 摘要：An adaptive fast filtering algorithm is proposed for the filtering problem about gray-scale image is that polluted by salt and pepper noise of different degree. This algorithm protects image details by using different filtering schemes for pixels’ different character; and controls iteration number adaptively by means of possible noise density. In this way to remove salt and pepper noise with different density. In addition, this algorithm proposes a statistical collation recording method based on string to reduce the number of statistical collation, in this way the time cost of this algorithm’s one time filtering process equals to that of the standard median filtering algorithm. The experiment shows that this algorithm has strong adaptive ability, high calculating efficiency and can achiere good filtering results.关键词：salt and pepper noise;filtering;adaptive;collation4139|309|0更新时间：2024-05-07
- 摘要：A new image denoising method based on Dual-tree complex wavelet combining partial differential equation in image denoising is presented. Image denoising with Wiener filter can not keep the edges of the image well enough due to the lack of directional ability in common tensor wavelet transform. Authors use the complex wavelet which has stronger directional ability and locally 6 directional Wiener filter to get a “clearer image”, then use “clearer image” guidance the diffusion function of partial differential equation to reduce noise in the image.Results of experiment show: the recovered images have higher PSNR and better visual quality than DTCW and PDE.关键词：dual-tree complex wavelet;directional wiener filtering;partial differential equation;diffusion function;image denoising3513|319|0更新时间：2024-05-07
- 摘要：Conventional image interpolation introduces blur and jagged edges. Existing improved interpolation algorithm obtains better visual quality of interpolated images than traditional interpolation algorithm. But interpolated images may still introduce jagged edges or distortion around the edge. To solve the problem, the paper proposes an improved adaptive image interpolation algorithm with gradient features. The basic idea is to first correct the special distance of interpolated pixels along one dimension on the basis of the local asymmetry features and gradient features of the original images, convert the corrected results of one dimension into two dimensions and then apply the corrected distance to conventional interpolation algorithm. Experimental results demonstrate that the improved method produces good results in regard to the peak signal-to-noise ratio(PSNR)and succeeds in preserving interpolation image edges of various directions.关键词：image interpolation;distance correction;gradient;edge preserved3996|291|0更新时间：2024-05-07
- 摘要：Straight line reconstruction model is frequently used in concrete computerized tomography. It assumes the ray travels in a straight line between a sending transducer and a receiving transducer, which is valid for homogeneous medium. When there are defects in the medium, the ray will not travel in a straight line but in a spatial curve, and if still using straight line reconstruction model, error will be brought in. An improved algebraic reconstruction technique (ART)is put forward in the paper, and linear travel time interpolation (LTI)ray tracing is used during the iterations to obtain the real travel paths of rays. Firstly, defect meshes are ascertained by probability and mathematical statistic method, and then defect meshes and normal meshes are provided with different initial wave velocities. Secondly, the projection matrix is anew computed by LTI ray tracing before each iteration. And during each iteration, defect meshes and normal meshes are provided with different relaxation factors. The results of computer simulation and concrete model experiment show that the improved ART based on LTI ray tracing is effective to improve the accuracy of computation and the quality of image reconstruction on concrete，but takes more time.关键词：concrete;image reconstruction;computerized tomography;ray tracing3577|230|0更新时间：2024-05-07
- 摘要：A new combinational scheme based on fusing and enhancing dual-energy X-ray hand luggage images is proposed in terms of X-ray image features. First, images are de-noised and fused with DWT (discrete wavelet transform), and then enhanced in fuzzy space with fuzzy theory. The proposed method in this paper is compared with that based on GLG (gray level grouping)and HE (histogram equalization). Experimental results show that the new method can improve the image definition efficiently and have better generalization.关键词：X-ray images;image fusion;wavelet transform;fuzzy enhancement3392|272|0更新时间：2024-05-07
- 摘要：A wavelet watermarking technique combined with fractal coding is proposed. First, a host image is partitioned into a set of non-overlapping square blocks. These blocks are sorted to become a descending sequence according to their collage errors which are obtained by performing baseline fractal coding, and two equal-length subsequences are chosen respectively according to the watermark size. Second, the watermark, which is first scrambled using arnold transform, is embedded into low-frequency bands in wavelet domains of distinct blocks in the two selected subsequences by a new embedding formula. Last, the watermark is the fusion of the extracted watermarks from the two selected subsequences. The experimental results show that this technique achieves good perceptual invisibility and security, and is also very robust against some image processing such as cropping, adding noise, scribbling, filtering, rotation and JPEG compression.关键词：image watermarking;fractal coding;collage error;fusion3219|226|0更新时间：2024-05-07
- 摘要：Accurately estimating the channel distortion for the video communication is significant to the joint power and rate-distortion (P-R-D)optimization. This paper proposes a channel distortion estimation model based on MPEG-4 coding stream. The model recursively estimates the channel distortion of the video coding sequences according to the bit error rate of the channel and the video coding information obtained in the video encoder. Simulation results demonstrate that the average relative estimation error and the average absolute estimation error introduced by the model are small. The model is applicable for the relative optimizations based on P-R-D.关键词：video communication;rate-distortion;channel distortion estimation model;MPEG-43404|275|0更新时间：2024-05-07
- 摘要：In this paper,a noval second generation watermarking algorithm based on image corner feature is proposed.Firstly, the watermark image is scrambled by using Arnold transformation. Secondly, wavelet transformation based three-level lifting for the carrier image is conducted. Thirdly, utilized the outcome of second step and MSP method, corners are detected from the low frequency components. Finally, by taking corners as root nodes, all the corresponding high frequency coefficients are extracted. Inverse operation of embedding watermark is performed with those coefficients. And using the given key, the watermark can be obtained. Sufficient experiments demonstrate the robustness of this approach, especially in resisting geometry attack such as RST (Rotation, Scaling and translation)and cut attack.关键词：digital watermarking;lifting-based wavelet;image corner feature;robust;geometry attack;image scrambling3381|280|0更新时间：2024-05-07
- 摘要：In the block-based FRUC algorithm, block size directly affects the accuracy of motion estimation and the visual quality of interpolated frame. To this end, a new motion adaptive FRUC algorithm is proposed. Firstly, STGS image which analyzes the content of the frame is introduced to select a suitable block size adaptively for each frame according to the motion feature. Then motion vectors are obtained by using OBME (overlapped block motion estimate). Furthermore, the MVIR (motion vectors interpolated refinement)along the block boundaries is performed to reduce the block artifacts, which is capable of smoothing the motion vectors field and reducing block effect. Experimental results show better performance of the proposed algorithm compare with traditional block-based FRUC algorithm.关键词：FRUC（frame rate up-conversion）;changed size blocks;STGS（spatio-temporal gradient scale） image;motion vectors refinement;motion estimation;motion compensation3400|247|0更新时间：2024-05-07
- 摘要：Encryption algorithm is used to ensure the transmission safety of multimedia data. Not only the security of algorithm, but also the compression efficiency and encryption complexity should be taken into consideration when design an encryption scheme. A new encryption scheme for image transmission is proposed in this paper, which is based on duple permutation. Firstly the original image is divided into several macro blocks in the light of certain size, and macro block within each row are permuted. Then, the first random S of AC coefficients in each 8×8 matrix are permuted after DCT （discrete cosine transform)and quantization. Theoretical analysis and experimental results indicate that the scheme proposed in this paper is secure and fast. It has little adverse impact on the compact ratio, 6.478％ by average. Moreover, it is format compatible and robust to transmission errors. All the attributes mentioned above make this algorithm suitable to be the encryption approach for image transmission.关键词：image;encryption;duple permutation;macro block3646|231|0更新时间：2024-05-07
- 摘要：The road edge identification is one of the key technology of the intelligent vehicle based on machine vision. A road edge identification and tracking algorithm based on linear road model is developed in this paper. This algorithm includes two stages, one is initial road identification algorithm and the other is road tracking algorithm. Pretreat the image at first at initial road edge identification stages, and then scan the image per-line in order to search the possible road edge points of every row. The method of Hough transform (HT) is used to match these points according to some road constrains. The new idea of this method is to set up the object search area (OSA) firstly at the road tracking stage, and the width of OSA is changing according to the change of the road edge identification reliability. And the possible road edge points are matched by Randomized Hough transform(RHT) method, This algorithm can decrease the algorithm running time and storage space evidently. Experiments prove that the algorithm is robust and fulfills the requirement real time of road edge identification.关键词：intelligent vehicle;road edge identification;OSA（object search area）;randomized Hough transform3750|353|0更新时间：2024-05-07
- 摘要：We present a PCA-based edge detection method with analysis on the orientation character of PCA. PCA translates the original data set to feature components in low dimension space using Karhunen-Loéve transform，which shows the tendency on energy collection and data selection. We point out and prove these orientation characters，and then present the new detection method TPCA，which processes an image with twice principal component analysis. First，an image is analyzed with PCA，and the residual is retained. Then，the image’s transpose is processed using PCA again，and the residual is transposed too. Finally，the two residuals are added. A better edge will be producted just with some simple operates，such as binary process. Experimental results show that the algorithm is effective,stable and has its own advantages compared with the traditional algorithms.关键词：edge detection;area;PCA;Twi-PCA（TPCA）4026|324|0更新时间：2024-05-07
- 摘要：For tracking and measuring maneuvering target in sports video frequency ， Kalman Filter(KF) and Extended Kalman Filter (EKF) has been widely used,but with low accuracy. A model that is combined with Interaction Multiple Model (IMM) algorithm and Debiased consistent Converted Measurements Kalman Filter (CMKF-D) algorithm is proposed for tracking and measuring the target in sports video frequency . It avoids the error that may be caused by transferring non-linear model to linear model through EKF and KF. The football video frequency simulation shows this algorithm can promote the tracking performance of maneuvering target in sports video frequency.关键词：video image;interaction multiple model(IMM);CMKF-D;maneuvering target tracking3794|262|0更新时间：2024-05-07
- 摘要：The three-dimensional shape descriptors have been applied to object recognition and classification. A novel three-dimensional shape descriptor combined with local and global representations is proposed in this paper. Firstly，traditional moment invariants are extended by including a term to represent spatial curvature and a series of new moment invariants named spatial curvature moment invariants is constructed. Secondly，normalization method of these invariants is presented and they are independent of the translation，rotation and scaling transforms. Experiments indicate the proposed method is of lower computation complexity than traditional three-dimensional shape descriptors without reducing the recognition rate.关键词：spatial curvature;moment invariants;differential geometry;pattern recognition3290|189|0更新时间：2024-05-07
- 摘要：Real-time segmentation of moving objects in image sequences is a fundamental step in many vision systems including intelligent visual surveillance and visual traffic analysis.Moving object detection has two key problems presently，one is the accuracy of background modeling，and the other is the disturbance from moving shadows.This paper presents a real-time background subtraction and moving shadow detection method based on Unscented Kalman Filter(UKF)，and constructs the whole frame for moving object detection.Background and moving shadow are modeled firstly.Then，dynamic character of pixel value is analyzed through frame to frame differencing and background differencing，and moving shadows are detected using luminance and chromatic cues of shadow.Finally，model parameters are updated online using UKF，and real-time segmentation of moving objects are completed.Our method exceeds existing ones at background maintenance speed，moving detection effect，and it has simple computational procedure.The experiments demonstrate the effectiveness and practicality of this method.关键词：moving object detection;background subtraction;shadow detection;unscented Kalman filter（UKF）3285|272|0更新时间：2024-05-07
- 摘要：As an important improvement of geodesic active contour model, gradient vector flow geodesic active contour model enlarged the applicability of geodesic active contour and improved its segmentation effect. Because the external force driving the evolution of active contour derived from gradient vector flow, active contour may be trapped into undesired local minimum due to some reasons, such as weak edges. In order to decrease the limitation of active contour’s initial location and the negative influence of weak edges on the evolution of active contour, we proposed a new gradient vector flow geodesic active contour model aided region force. This model combined external force field based on region information with gradient vector flow force field. This coupling external force field enables geodesic active contour to overcome the influence of weak edges and converge desired boundary. Experimental results show that gradient vector flow geodesic active contour model aided region force has more flexibility to determine the initial contour，better adaptability to the disturbance of weak edges and can effectively avoid boundary leakage compared with gradient vector flow geodesic active contour model.关键词：image segmentation;geodesic active contour model;gradient vector flow;region force3807|259|0更新时间：2024-05-07
- 摘要：All of the existed algorithms in face recognition, which can obtain uncorrelated discriminant vectors, are based on image vector model, so they encounter so called “small sample size” problem. These algorithms, which are solved using recursive methods, require much computation time. So a new algorithm is proposed in this paper, which is called Two-dimensional Uncorrelated Discriminant Vectors based on an image matrix model. The new algorithm solves small sample size problem through whitening transform of within-class scatter matrix, which makes the model of extended Two-dimensional Linear Discriminant Analysis have similar form of Two-dimensional Principal Component Analysis model. Thus two algorithms were combined effectively, uncorrelated discriminant vectors can be obtained non-recursively. The new method computes fast while maintaining numerical stability. The numerical experiments on facial databases of ORL and Yale show that the proposed method has not only reduced the computation complexity but also achieved higher recognition accuracy, providing new thought on how to obtain uncorrelated discriminant vectors.关键词：two-dimensional uncorrelated discriminant vectors;image matrix model;whitening transform;scatter matrix;non-recursively3198|221|0更新时间：2024-05-07
- 摘要：The color of the figures printed with photo-induced discoloration ink has a special change when the light irradiates a bank note from different angles. This is an important method to identify if a bank note is faked or not. In this paper, an automatic recognition method focusing on photo-induced discoloration printed ink technique is proposed to recognize the fakeness of bank notes. The bank note automatic recognition system mainly consists of DSP, FPGA and color CCD camera. The system pre-handles video data stream by FPGA, sequentially switches among different memory areas and completes the real-time collection and storage of bank note image data. According to the characteristics of the image data, based on the concept of SOPC, FPGA integrates Nios soft core and implements parallel processing. Then DSP completes the recognition process of a bank note. The feasibility and effectiveness of the proposed automatic recognition method is verified by various experiments.关键词：bank note recognition;photo-induced discoloration printed ink;DSP（digital signal processor）;FPGA（field-programmable gate array）;SOPC（system on a programmable chip)3376|270|0更新时间：2024-05-07
- 摘要：Features detection is an important problem in image processing and pattern recognition, the detection result affects the pattern recognition and classification directly. Based on the idea of multi-scale geometric analysis, this paper introduces a new method to detect circles in digital images. Firstly, circles in images are transformed into circles feature domain. Then wavelet analysis is applied in the domain to detect point singularity. The coordinate of singular point is the coordinate of circle to be detected. Gray threshold or grads will be applied when Hough transform is used for gray image to detect circle. This disadvantage is overcome by the new method, and it is directly used for gray image or binary image to detect multi-circle. Finally, the difference between the new method and Hough transform is analyzed and compared.关键词：image;circle feature;multi-scale geometric analysis;detection3749|276|0更新时间：2024-05-07
- 摘要：Descriptor of features point is vital application of many computer vision tasks. Therefore, this paper presents a novel algorithm to design the descriptor of image feature points based on differential histograms under polar coordinates (HWDH).Firstly, the neighbor area of feature point is divided into nine small patches. Then, Gradient differential is produced by harr wavelet on every small patch and a dominant direction of the feature point is computed by Scale Adapted Harris detector which is improved. Lastly, histogram is generated from the differential statistic. In contrast to other descriptor based on differential histograms， the description generated by our algorithm needn’t to rotate in the around area of feature point. Therefore, it can deduce the error from statistic. Moreover, the comparative experiments illustrated that the proposed algorithm is more rapid and accurate than SIFT.关键词：scale-invariant feature transform（SIFT）;dominant directions;descriptor3422|220|0更新时间：2024-05-07
- 摘要：The structure element (SE) used in morphology operation is extended to superposition of SE, short for SSE, inspired by the quantum information processing theory.The SSE’s has no fixed sizes or form and its scale is described with the limits of size. SSE is linear superposition of all SE available in its limits of size. SSE can be collapsing and returns to a SE when a measurement on it is taken. The morphological operators, named by collapsing morphological operators, based on quantum measurement and collapsing are defined,and then a self-adapted filtering operation is created by applying these operators in this paper. The results obtained in the computer simulation on image filtering using this operation is shown that this self-adapted filtering has more powerful ability for denoising than median filter and corresponding traditional morphological filter and are independent of the intensity of noise.3564|231|0更新时间：2024-05-07
- 摘要：RANSAC is the most widely used robust regression algorithm in computer vision.Starting from the Tc,d pre-evaluation model of RANSAC algorithm，a two-step method is presented for optimal (c,d) selection. Based on this method，the adaptive Tc,d test extension is proposed to achieve user independent RANSAC acceleration. We show experimentally that using both short-baseline and wide-baseline epipolar geometry estimation，the proposed method is up to 400% faster than the standard RANSAC.关键词：random sample consensus（RANSAC）;pre-evaluation;robust estimation;fundamental matrix;local optimization4629|277|0更新时间：2024-05-07
- 摘要：Imposing data-closeness as a hard constraint to needle-map of surface is proved to be a successful approach of shape from shading(SFS)technique in recent years, but the initialization needle map of the algorithm is much different from the true one of surface when the light source direction is not vertical and the uniqueness of needle map cannot be ensured.Aiming at avoiding the drawbacks of the algorithm based on the hard constraint, a modified method is presented in this paper.After the relationship of image gradient map and surface needle map is analyzed, the positions of the local brightest points of image are firstly detected and the positions of the local highest points of surface are estimated according to the irradiance equation.Secondly, at each point, the gradient direction of image is updated and the equation group is set up.For different cases of the equations, corresponding solutions are presented in this algorithm.The modified algorithm is effective when the illuminant direction is either vertical or non-vertical and the applicability of the algorithm is improved. Experimental results on synthetic and real images show that much accurate initial needle map and height are obtained.关键词：shape from shading（SFS）;hard constraint;needle map;estimating of the local highest points;updating of gradient direction3662|262|0更新时间：2024-05-07
- 摘要：Surfaces smoothing has been widely used in computer aided geometry design(CAGD). Digital surface with noise can be looked as non-stationary discrete geometry signal. Empirical mode decomposition (EMD) is a new method for non-stationary signal analyzing. In this paper, novel methods for spatial curves smoothing by EMD and four-side region surfaces smoothing with 2D separable EMD are presented.Four-side region digital surface can be represented as a mesh formed by U and V discrete curves. In spatial curve smoothing, we parameterize the digital curve to 1D, and transform the curve to 1D signal firstly. Then decompose the 1D signal into a collection of intrinsic mode functions (IMF) by using EMD. Thirdly, remove the high frequency IMFs and reconstructing the signal. Finally, mapping the reconstructed signal to 3D, and the smoothing curve is obtained. During the four-side region surface smoothing, smooth each U curve of the surface first and then each V curve with the spatial curve smoothing method. Experiments show that noises in the surface can be removed efficiently, and good results are obtained by using the smoothing method.关键词：surface smoothing;four-side region surface;EMD（empirical mode decomposition）;IMF（intrinsic mode functions）3887|235|0更新时间：2024-05-07
- 摘要：The structural features and spatial relations in a digital terrain are definitive manner in terrain simulation by computer. It determines whether a digital terrain is similar to the natural ones. In the natural environment rivers are embedded in mountains. To bring this spatial modality into a stochastic terrain built by computer, a new method is introduced in this paper. In the method, a valley line is generated from a revised DLA model (Diffusion Limited Aggregation) controlled by sticking coefficient and mean field parameter. After a simplification of the valley line, a continuous expanding operation is used to establish the digital terrain subsequently. The experiment result shows that this method is controllable in the process of establishing the terrain. And the terrain is stochastic with natural dendritic valley in it.关键词：valley structure;digital terrain;DLA model;extended parameters3986|252|0更新时间：2024-05-07
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