Integrating modern artificial intelligence (AI) techniques, particularly generative AI, holds the promise of revolutionizing computer-aided design (CAD) tools and the engineering design process. However, the direction of “AI+CAD” remains unclear: how will the current generation of intelligent CAD (ICAD) differ from its predecessor in the 1980s and 1990s, what strategic pathways should researchers and engineers pursue for its implementation, and what potential technical challenges might arise?As an attempt to address these questions, this paper investigates the transformative role of modern AI techniques in advancing CAD towards ICAD. It first analyzes the design process and reconsiders the roles AI techniques can assume in this process, highlighting how they can restructure the path humans, computers, and designs interact with each other. The primary conclusion is that ICAD systems should assume an intensional rather than an extensional role in the design process. This offers insights into the evaluation of the previous generation of ICAD (ICAD 1.0) and outlines a prospective framework and trajectory for the next generation of ICAD (ICAD 2.0).

Model classification is essential to the management and reuse of 3D CAD models. Manual model classification is laborious and error prone. At the same time, the automatic classification methods are scarce due to the intrinsic complexity of 3D CAD models. In this paper, we propose an automatic 3D CAD model classification approach based on deep neural networks. According to prior knowledge of the CAD domain, features are selected and extracted from 3D CAD models first, and then preprocessed as high dimensional input vectors for category recognition. By analogy with the thinking process of engineers, a deep neural network classifier for 3D CAD models is constructed with the aid of deep learning techniques. To obtain an optimal solution, multiple strategies are appropriately chosen and applied in the training phase, which makes our classifier achieve better performance. We demonstrate the efficiency and effectiveness of our approach through experiments on 3D CAD model datasets.

In this paper, we present an approach to semantic cage generating and semantic cage based finite element mesh editing to allow users to conduct the required editing on complex finite element mesh effectively and efficiently through cage-based deformation during product design. In the approach, design semantics involved in a finite element mesh are incorporated with its cage to enable the cage based and semantic based editing of the finite element mesh. Firstly, the design semantics including semantic features and semantic relations are extracted from the original mesh, and a simplified mesh with the semantics preserved is constructed. Then, the semantic cage without cage-model intersection is automatically created by offsetting the simplified mesh and mapping the semantics from the original mesh to the cage. Finally, the editing manipulation is directly imposed on the semantic features rather than single vertex or face of the cage to achieve the required modification on the mesh. The experimental results show the effectiveness and potentials of the proposed approach.

Volumetric mesh models are widely used nowadays in areas like product quality evaluation, physically-based deformation, numerical simulation, and so on. In the application of Computer Aided Design (CAD) and Computer Aided Engineering (CAE) integration, providing a method to directly manipulate mesh models can reduce much effort in the simulation process. However, this integration is limited or only provided from CAD to CAE at current time. In this paper, we propose a framework for volumetric mesh editing based on feature dimensions. In our framework, the volumetric mesh is first decomposed into volumetric features based on corresponding surface features. Then, random-walk based interpolation algorithm is applied to manipulation of local features. Our framework allows users to change the dimensions of the recognized features on the volumetric mesh directly. Then optimization, which is limited to local features, is employed to refine the tetrahedrons of the volumetric features once the quality of the elements does not meet the requirements. Experimental results show that the features hold precisely after the editing operations. Additionally, the quality of the elements keeps well after the tetrahedral mesh has been edited.

In the process of numerical simulation, Finite Element Analysis (FEA) is commonly used for product design optimization. The product model has to be modified according to its associated optimization result obtained based on analysis, and the mesh model needs to be regenerated for analysis to verify the modification. In order to reduce the time for mesh regeneration, one effective way is to directly edit the mesh model according to the modification requirements. In this paper, we present a novel mesh editing method for FE mesh models. The approach achieves the complex and accurate modification on FE mesh models through CAD operations and limits the remeshing to the modified region of the whole mesh model so as to make the approach efficient. Firstly, sweeping operation and Boolean operation are used to construct the new geometry on the mesh model according to the modification requirements, taking the mesh elements as the reference of the operations. Then, mesh geometry fusion is conducted, making the related mesh elements aligned with the intersection lines between the original mesh model and the newly added geometry through node repositioning. Finally, mesh elements for the newly added geometry are generated and optimized. Compared with traditional mesh editing methods, the proposed approach can achieve complex editing of FE mesh model more effectively and efficiently. And the preliminary experimental results show the potentials of the proposed approach.

This paper presents a simplification method for B-rep (boundary representation) models through region suppression. It suppresses every complex unwanted region of a B-rep model as a whole so as to effectively and efficiently generate a simplified version of the original model that preserves the rough shape. In this method, the new surfaces that are used to cover each suppressed region are constructed based on the decomposition of the boundary loops of the suppressed region, rather than through the time-consuming face extension and intersection operations widely adopted by previous works. The experimental and evaluation results are given to show the efficiency and robustness of the method.

Mesh editing can provide various models for FEA-simulation in industry. This paper proposes a framework for FEA-mesh editing with feature constrained. In the framework, cage-based technique is first used to edit the base-decomposition model. Vertices of the constrained feature are transformed into a local form. Parameters are analyzed before editing operation, and our method permits the user to add constraints on the parameters of the feature. This framework can also keep consistence for the disconnected assembly mesh model. Experimental results show that constrained features are kept precisely after mesh editing. Additionally, experimental data indicate our method is efficient and achieves real-time response.

In this paper, we present a semantic-based partial retrieval approach of CAD models for design reuse. Based on the observation of reusable regions for design of 3D CAD models, for each model in the model library, we propose an algorithm that automatically extracts its reusable regions for partial retrieval. To further effectively support the partial retrieval of these reusable regions through simple queries, we represent each reusable region by all its local matching regions and describe each local matching region in a hierarchical way. Based on the hierarchical descriptor, a partial retrieval method for reusable regions is put forward. The approach proposed is implemented and tested by hundreds of mechanical parts. Preliminary results show that the method can effectively support partial retrieval for design reuse.

The coarse bounding cage of a dense mesh plays important roles in computer graphics, computer vision, and geometric design. Specifically, in volume-based deformation, a coarse bounding cage is required to manipulate the dense mesh model it enclosed; in subdivision surface fitting, the fitting starts from a coarse cage bounding the fitted dense mesh or point set; and so on. However, the generation of a coarse bounding cage is mainly by interactive ways, which are very tedious and time-consuming. In this paper, we develop a fully automatic method to generate a coarse cage bounding a dense mesh model. The automatically generated coarse bounding cage can keep the topological structure and major geometric features of the original mesh model, which is validated by theoretical analysis and experimental data presented in this paper. Further more, we employ the automatically generated coarse bounding cage in some applications, such as deformation, and subdivision fitting, producing good results.

The significance of tolerance is obvious and undoubted for product design and manufacturing. However, it is not intuitionistic for the computer to understand the tolerance semantics, which heavily baffles the integration of CAD and CAM. In this paper, a uniform approach to interpreting the rigorous tolerance semantics for complicated tolerance specification (CTS) is proposed with the help of reclassification of tolerance based on tolerance zone (TZ). First, the tolerance is reclassified into three categories: Immovable-TZ (ITZ) tolerance, Translational-TZ (TTZ) tolerance and Floatable-TZ (FTZ) tolerance. Second, a uniform method of interpreting the rigorous tolerance semantics is presented based on the variation along degrees of freedom direction (VDOF) for CTSs. To improve the computational efficiency of implementation of interpreting rigorous tolerance semantics, a novel method is proposed to determine the TZ boundary without performing Boolean intersection operations in 3-D CAD systems. Finally, the algorithm is implemented and some test results are given.

A good concurrency control method that maximizes the operational parallelism while prevents conflicts of simultaneous manipulations is vital for cooperative design systems and still a challenge. We propose an adaptive granular concurrency control approach for the replicated collaborative feature modeling based on the feature dependency directed acyclic graph (FDAG). According to the varying design contexts, an adaptive granularity for concurrent manipulations is determined dynamically by the FDAG of the replicated model to avoid concurrent regeneration conflicts. A prototype is realized on a real-time collaborative design system consisting of heterogeneous CAD systems. The preliminary results show that the approach proposed is promising.

According to the characteristics of CAD mesh model and the requirements of engineering applications, we propose a novel method of simplifying CAD mesh model. First, the model is segmented using an improved watershed segmentation algorithm, and the region-level representation required by feature recognition is set up. Second, the form features needing to be suppressed are extracted through feature recognition and the feature-level representation is established. Third, every recognized feature is suppressed in a proper way and the simplified model is obtained finally. Several experimental results are given to show the superiority and effectivity of our approach.

In this paper, a multi-mode retrieval approach of solid models is presented. First, a local feature determination method based on wavelet transform is given, which makes the local feature agree with the human perception of resemblance; then a uniform and efficient DBMS (dilation based multiresolutional skeleton) generation method for global model and local feature using adaptive voxelization and local dilation is proposed; finally a flexible similarity assessment is proposed which supports both global matching and partial matching effectively and further supports different retrieval requires. Preliminary experiment results show that a multi-mode retrieval approach can describe user's retrieval intent more precisely and return retrieval results more properly.

A parallel global optimal approach of feedback is proposed for 3D CAD model retrieval in this study. First, a novel unified mathematical model with multi-object for similarity field modification based relevance feedback is brought forward and the simplification is also given. Second, a new algorithm based on particle swarm optimization is proposed to optimize above model. In this algorithm, the particle can fly under the guide of its experience and a leader queue helps to avoid immature convergence. At last, an implementation is given and the results show that better feedback results are obtained for CAD model retrieval with the proposed method.

Medial axis (MA) is widely used in many fields nowadays. However, the efficiency of generating MA of complicated models with current methods is still not satisfactory. A novel approach to constructively generate MA is proposed in this paper. With this method, the MA of the resultant model set up with two primitives and a Boolean operation upon them is generated by combining the MAs of the two primitives in a certain way instead of regenerating from scratch. First, the properties of MA are investigated. During Boolean operation, the boundaries that will vanish are found and the region of the model on the basis of which some new MA segments(MASs) need to be generated is determined, and the new MASs are generated based on the region using tracing method. The MA of the resultant model is constructed by combining the new generated MASs with the reserved MASs of the two primitives at last.

Summary form only given. This paper presents a novel hole-filling algorithm that can fill arbitrary holes in triangular mesh models. First, the advancing front mesh technique is used to cover the hole with newly created triangles. Next, the desirable normals of the new triangles are approximated using our desirable normal computing schemes. Finally, the three coordinates of every new vertex are re-positioned by solving the Poisson equation based on the desirable normals and the boundary vertices of the hole. Many experimental results and error evaluations are given to show the robustness and efficiency of the algorithm.

Concurrency control with a reasonable granularity is one of open challenges in cooperative design systems. In this paper, a fine granular concurrency control mechanism is proposed to support simultaneous feature modifications during cooperative design activities. First, extend a de-centralized mutual exclusion agreement on a single critical section to a fully distributed concurrency control mechanism supporting multiple critical sections. Second, a feature-level concurrency control framework is devised for peer-to-peer cooperative design environments to ensure the consistency of replicated models after concurrent manipulations. Finally, a prototype of the proposed mechanism is realized on a real-time cooperative design environment consisting of two heterogeneous CAD systems, SolidWorks and Autodesk Mechanical Desktop.

The top-down collaborative assembly design process of a product is highly concurrent. Rational task planning significantly affects cycle and efficiency of the product design. This paper discusses the task planning for top-down collaborative assembly design which contains task grouping and task group assignment. A genetic algorithm for the task grouping is developed according to two principles: one is that the workload should be equilibrium among the design teams; the other is that the tasks with high coupling relationships should be grouped into the same task group. And the algorithm for task group assignment is presented according to criticality of the task group and comprehensive capability of the design team. As a case, top-down collaborative assembly design of the shaper is demonstrated

Tolerance is almost ubiquitous during the whole product life. However how to effectively embody and interpret the semantics of tolerance in three-dimensional computer-aided design systems is still an open issue. Variational geometry is recognized as one of the most promising solution for it. And the methods for systematically and efficiently generating the variational geometries of all kinds of geometric entities with tolerances are imperative. In this paper, a degree-of-freedom (DOF)-based approach is proposed for generating variational geometry of a hole with composite tolerances imposed on its centerline and surface at the same time. All possible combinations of tolerance requirements for a hole are discussed. And the mathematical models for variational geometries of the centerline and the surface of a hole are deduced. Furthermore two strategies for improving the efficiency of generating the variational geometry of a hole are presented. Finally, the algorithm is implemented and some test results are given. Note to Practitioners-This paper is motivated by the problem that the tolerance information in the current computer-aided-design CAD systems lacks the necessary engineering semantics, which causes tolerance information that cannot be correctly used and impedes the integration of CAD and computer-aided manufacturing (CAM). Existing approaches have partially solved the problem for the pattern of holes (POH) and plane feature based on variational geometry. But the computational efficiency with the variational geometry method is very insufferable due to a lot of Boolean intersection operation. In this paper, the hole feature is mainly considered because its tolerance specification is quite different from other features and is imposed on the centerline and the surface of a hole at the same time. First, the mathematical model is given for interpreting the engineering semantics of the tolerance of the centerline and the surface based on the variational geometry, respectively. Then, the tolerance principles are further considered for compensation between the above two types of tolerance. More important, a direct method, which can largely avoid the Boolean intersection operation, is proposed for generating the variational geometry. The computational efficiency is thus improved dramatically and the variational geometry is generated almost in real time. This enables virtual assembly and virtual inspection with the tolerance information to be possible.

Haptic rendering is a highly device-dependent process. Accordingly, haptic rendering algorithms should be designed regarding the specific physical features of a haptic device. The Immersion CyberGrasp is a force feedback device which can provide an individual force roughly perpendicular to the fingertip of each finger. In this paper, we propose a novel force rendering algorithm for the Immersion CyberGrasp considering the feature of area contacts between the virtual hand avatar and target geometric models. Line segment clusters are used as haptic proxies for the real-time collision detection between the fingertips and target geometric models. Force computations are conducted directly using the collision detection results. Spatial subdivision is performed on target geometric models to facilitate real-time collision detection. Experimental results show that our algorithm can provide stable and realistic force feedback.

Exchange of procedural CAD models between heterogeneous CAD systems is still a challenging issue in CAD area. Previously we proposed an approach for effectively constructing synchronized collaborative design environment based on heterogeneous CAD systems. In this paper, we extend the synchronized collaborative design environment that we have developed to a Web services based platform for exchange of procedural CAD models between heterogeneous CAD systems. First, the real-time exchange of a single operation is extended to the exchange of the complete procedural CAD model between heterogeneous CAD systems. Furthermore, Web services technology is adopted to encapsulate the procedural CAD model exchange functions, which are then released on the Internet as a standard interface and can be used by remote developers in their windows applications, Web applications, and so on. Finally, a Web service for exchange of procedural CAD models between SolidWorks and Autodesk Mechanical Desktop is realized.

Along with the great advancement of remote sensing technology and extensive application of remote sensing information, more and more requirements on capability and efficiency for all kinds of interpreting system of remote sending images come out. The conventional interpreting systems commonly have the operating mode with one single interpreter and an isolated computer. But this conventional mode has a serious immanent limitation due to the isolation of position, personnel, data, software, hardware and so on. This paper provides a CSCW-based interpreting system of remote sensing imagery (RSI) to avoid the limitation from the conventional systems. This new system fully integrates the remote sensing technology and computer supported cooperative work (CSCW) technology, actualizes interpreting of RSI with a synchronized operation for multi-user. Consequently it greatly improves capability, efficiency, and accuracy. The better actual effect proves that interpreting system of RSI is feasible and effective.

Intuitive and natural interactions are key aspects of virtual assembly applications. In this paper, we present intuitive virtual hand interactions with parts, subassemblies and tools. Grasping patterns are developed based on the abstraction of various mechanic shapes, kinematics model of virtual hand is built upon the anatomic structure of the human hand to guarantee motion realism, and real-time collision detection scheme is used to identify whether the current finger configuration matches a specific grasping pattern. Experiments on assembly models with a CyberGlove dataglove show that our virtual grasping scheme works well for virtual assembly tasks.

Abstract Image‐based collision detection algorithms make efficient use of the graphics rendering hardware and reduce the computational cost of CPU. In this article, a fast collision detection algorithm based on image space is presented, which combines graphics hardware capabilities with a simplified geometric representation (oriented bounding box) in order to rapidly detect collisions between complex objects. The method can deal with arbitrary polyhedra, while preserving the merits of image‐based collision detection algorithms. This is achieved by decomposing the surfaces of an object into a list of convex pieces. High efficiency of the algorithm is obtained by organizing the convex pieces into a binary tree with each node representing a convex piece, and by adopting triangle strip compression. The algorithm has been implemented and compared with related algorithms. Copyright © 2003 John Wiley & Sons, Ltd.

This paper presents a feature-based approach to the automatic generation of an injection mold. In the approach, all the molding features of a molded part are recognized first using a universal hint-based feature recognition algorithm, and the optimal parting direction is determined based on the feature model. Then, all the faces related with the parting line are classified into three groups according to the determined parting direction, and two kinds of parting lines are automatically determined by extracting the largest profile of each face group. Finally, the parting surface is generated based on the optimal pacing line, thereafter the mold core and mold cavity are automatically set up by splitting the mold box of the molded part with the generated parting surface. By using recognized molding features, the approach makes it possible to identify all undercuts, to determine internal parting lines and internal parting surfaces, to generate the mold core and cavity of a complex molded part with undercuts as well.