Neural shape representation generally refers to representing 3D geometry using neural networks, e.g., computing a signed distance or occupancy value at a specific spatial position. In this paper we present a neural-network architecture suitable for accurate encoding of 3D shapes in a single forward pass. Our architecture is based on a multi-scale hybrid system incorporating graph-based and voxel-based components, as well as a continuously differentiable decoder. The hybrid system includes a novel way of voxelizing point-based features in neural networks by projecting the point "feature-field" onto a grid. This projection is insensitive to local point density, and we show that it can be used to obtain smoother and more detailed reconstructions, in particular when combined with oriented point clouds as input. Our architecture also requires only a single forward pass, instead of the latent-code optimization used in auto-decoder methods. Furthermore, our network is trained to solve the well-established eikonal equation and only requires knowledge of the zero-level set for training and inference. We additionally propose a modification to the aforementioned loss function for the case that surface normals are not well defined, e.g., in the context of non-watertight surfaces and non-manifold geometry. Overall, our method consistently outperforms other baselines on the surface reconstruction task across a wide variety of datasets, while being more computationally efficient and requiring fewer parameters.

We propose a transformer architecture and training strategy for tree generation. The architecture processes data at multiple resolutions and has an hourglass shape, with middle layers processing fewer tokens than outer layers. Similar to convolutional networks, we introduce longer-range skip connections to complement this multi-resolution approach. The key advantages of this architecture are the faster processing speed and lower memory consumption. We are, therefore, able to process more complex trees than would be possible with a vanilla transformer architecture. Furthermore, we extend this approach to perform image-to-tree and point-cloud-to-tree conditional generation and to simulate the tree growth processes, generating 4D trees. Empirical results validate our approach in terms of speed, memory consumption, and generation quality.

Thunderstorms are complex multiphysics phenomena driven by charge transfer processes arising from interactions between ice and water particles in the atmosphere. We present a physically grounded model for simulating cloud electrification and lightning discharge, capable of generating diverse lightning types as emergent responses to evolving atmospheric conditions. Our approach requires only a minimal set of atmospheric parameters and no user-defined triggers. Charge separation is modeled at the microphysical level using a statistical mechanics framework, while discharges are captured through a novel gauge-invariant dielectric breakdown model that accounts for bipolar channels, dynamic electric fields, and air resistance. We validate our method through comparisons with observational data and prior models, demonstrating its ability to simulate distinct discharge types and the full life cycle of thunderstorms. Beyond scientific accuracy, our framework supports real-time nowcasting, civil engineering assessments, virtual environment generation, and the simulation of complex dielectric breakdown in varied contexts.

We investigate the capabilities of neural inverse procedural modeling to infer high-quality procedural yarn models with fiber-level details from single images of depicted yarn samples. While directly inferring all parameters of the underlying yarn model based on a single neural network may seem an intuitive choice, we show that the complexity of yarn structures in terms of twisting and migration characteristics of the involved fibers can be better encountered in terms of ensembles of networks that focus on individual characteristics. We analyze the effect of different loss functions including a parameter loss to penalize the deviation of inferred parameters to ground truth annotations, a reconstruction loss to enforce similar statistics of the image generated for the estimated parameters in comparison to training images as well as an additional regularization term to explicitly penalize deviations between latent codes of synthetic images and the average latent code of real images in the encoder’s latent space. We demonstrate that the combination of a carefully designed parametric, procedural yarn model with respective network ensembles as well as loss functions even allows robust parameter inference when solely trained on synthetic data. Since our approach relies on the availability of a yarn database with parameter annotations and we are not aware of such a respectively available dataset, we additionally provide, to the best of our knowledge, the first dataset of yarn images with annotations regarding the respective yarn parameters. For this purpose, we use a novel yarn generator that improves the realism of the produced results over previous approaches.

Cyclones are large-scale phenomena that result from complex heat and water transfer processes in the atmosphere, as well as from the interaction of multiple hydrometeors , i.e., water and ice particles. When cyclones make landfall, they are considered natural disasters and spawn dread and awe alike. We propose a physically-based approach to describe the 3D development of cyclones in a visually convincing and physically plausible manner. Our approach allows us to capture large-scale heat and water continuity, turbulent microphysical dynamics of hydrometeors, and mesoscale cyclonic processes within the planetary boundary layer. Modeling these processes enables us to simulate multiple hurricane and tornado phenomena. We evaluate our simulations quantitatively by comparing to real data from storm soundings and observations of hurricane landfall from climatology research. Additionally, qualitative comparisons to previous methods are performed to validate the different parts of our scheme. In summary, our model simulates cyclogenesis in a comprehensive way that allows us to interactively render animations of some of the most complex weather events.

Plants are among the most complex objects to be modeled in computer graphics. While a large body of work is concerned with structural modeling and the dynamic reaction to external forces, our work focuses on the dynamic deformation caused by plant internal wilting processes. To this end, we motivate the simulation of water transport inside the plant which is a key driver of the wilting process. We then map the change of water content in individual plant parts to branch stiffness values and obtain the wilted plant shape through a position based dynamics simulation. We show, that our approach can recreate measured wilting processes and does so with a higher fidelity than approaches ignoring the internal water flow. Realistic plant wilting is not only important in a computer graphics context but can also aid the development of machine learning algorithms in agricultural applications through the generation of synthetic training data.

Computer graphics has dedicated a considerable amount of effort to generating realistic models of trees and plants. Many existing methods leverage procedural modeling algorithms - that often consider biological findings - to generate branching structures of individual trees. While the realism of tree models generated by these algorithms steadily increases, most approaches neglect to model the root system of trees. However, the root system not only adds to the visual realism of tree models but also plays an important role in the development of trees. In this paper, we advance tree modeling in the following ways: First, we define a physically-plausible soil model to simulate resource gradients, such as water and nutrients. Second, we propose a novel developmental procedural model for tree roots that enables us to emergently develop root systems that adapt to various soil types. Third, we define long-distance signaling to coordinate the development of shoots and roots. We show that our advanced procedural model of tree development enables - for the first time - the generation of trees with their root systems.

We introduce a novel method for reconstructing the 3D geometry of botanical trees from single photographs. Faithfully reconstructing a tree from single-view sensor data is a challenging and open problem because many possible 3D trees exist that fit the tree's shape observed from a single view. We address this challenge by defining a reconstruction pipeline based on three neural networks. The networks simultaneously mask out trees in input photographs, identify a tree's species, and obtain its 3D radial bounding volume - our novel 3D representation for botanical trees. Radial bounding volumes (RBV) are used to orchestrate a procedural model primed on learned parameters to grow a tree that matches the main branching structure and the overall shape of the captured tree. While the RBV allows us to faithfully reconstruct the main branching structure, we use the procedural model's morphological constraints to generate realistic branching for the tree crown. This constraints the number of solutions of tree models for a given photograph of a tree. We show that our method reconstructs various tree species even when the trees are captured in front of complex backgrounds. Moreover, although our neural networks have been trained on synthetic data with data augmentation, we show that our pipeline performs well for real tree photographs. We evaluate the reconstructed geometries with several metrics, including leaf area index and maximum radial tree distances.

The analysis and modeling of cloth has received a lot of attention in recent years. While recent approaches are focused on woven cloth, we present a novel practical approach for the inference of more complex knitwear structures as well as the respective knitting instructions from only a single image without attached annotations. Knitwear is produced by repeating instances of the same pattern, consisting of grid-like arrangements of a small set of basic stitch types. Our framework addresses the identification and localization of the occurring stitch types, which is challenging due to huge appearance variations. The resulting coarsely localized stitch types are used to infer the underlying grid structure as well as for the extraction of the knitting instruction of pattern repeats, taking into account principles of Gestalt theory. Finally, the derived instructions allow the reproduction of the knitting structures, either as renderings or by actual knitting, as demonstrated in several examples.

We propose a material classification method using raw time-of-flight (ToF) measurements. ToF cameras capture the correlation between a reference signal and the temporal response of material to incident illumination. Such measurements encode unique signatures of the material, i.e. the degree of subsurface scattering inside a volume. Subsequently, it offers an orthogonal domain of feature representation compared to conventional spatial and angular reflectance-based approaches. We demonstrate the effectiveness, robustness, and efficiency of our method through experiments and comparisons of real-world materials.

The aim of this study is to investigate visualization concepts by eliciting users' experience when using university campus maps. A pragmatic paradigm was applied to elicit subjective view of users' perception and aggregate their personal constructs in a more general, objective context. The methodological approach taken in this study was a mixed-method approach, in the form of repertory grid technique to elicit a list of factors when using a campus map. Thirteen usefulness factors of visualization were derived using thematic analysis. A triangulation between these factors and Principal Component Analysis results was conducted to provide more holistic classifications. This study offers important insights by adopting an uncommon paradigm in generating valuable data concerning the perceived characteristics of visualization based on users' perception.

Transient images help to analyze light transport in scenes. Besides two spatial dimensions, they are resolved in time of flight. Cost-efficient approaches for their capture use amplitude modulated continuous wave lidar systems but typically take more than a minute of capture time. We propose new techniques for measurement and reconstruction of transient images, which drastically reduce this capture time. To this end, we pose the problem of reconstruction as a trigonometric moment problem. A vast body of mathematical literature provides powerful solutions to such problems. In particular, the maximum entropy spectral estimate and the Pisarenko estimate provide two closed-form solutions for reconstruction using continuous densities or sparse distributions, respectively. Both methods can separate m distinct returns using measurements at m modulation frequencies. For m = 3 our experiments with measured data confirm this. Our GPU-accelerated implementation can reconstruct more than 100000 frames of a transient image per second. Additionally, we propose modifications of the capture routine to achieve the required sinusoidal modulation without increasing the capture time. This allows us to capture up to 18.6 transient images per second, leading to transient video. An important byproduct is a method for removal of multipath interference in range imaging.

This paper presents Oracle Database Replay, a novel approach to testing changes to the relational database management system component of an information system (software upgrades, hardware changes etc). Database Replay makes it possible to subject a test system to a real production system workload, which helps identify all potential problems before implementing the planned changes on the production system. Any interesting workload period of a production database system can be captured with minimal overhead. The captured workload can be used to drive a test system while maintaining the concurrency and load characteristics of the real production workload. Therefore, the test results using database replay can provide very high assurance in determining the impact of changes to a production system before applying these changes. This paper presents the architecture of Database Replay as well as experimental results that demonstrate its usefulness as testing methodology.

Use of technology often has unpleasant side effects, which may include strong, negative emotional states that arise during interaction with computers. Frustration, confusion, anger, anxiety and similar emotional states can affect not only the interaction itself, but also productivity, learning, social relationships, and overall well-being. This paper suggests a new solution to this problem: designing human–computer interaction systems to actively support users in their ability to manage and recover from negative emotional states. An interactive affect–support agent was designed and built to test the proposed solution in a situation where users were feeling frustration. The agent, which used only text and buttons in a graphical user interface for its interaction, demonstrated components of active listening, empathy, and sympathy in an effort to support users in their ability to recover from frustration. The agent's effectiveness was evaluated against two control conditions, which were also text-based interactions: (1) users’ emotions were ignored, and (2) users were able to report problems and ‘vent’ their feelings and concerns to the computer. Behavioral results showed that users chose to continue to interact with the system that had caused their frustration significantly longer after interacting with the affect–support agent, in comparison with the two controls. These results support the prediction that the computer can undo some of the negative feelings it causes by helping a user manage his or her emotional state.

Prototypes of interactive computer systems have been built that can begin to detect and label aspects of human emotional expression, and that respond to users experiencing frustration and other negative emotions with emotionally supportive interactions, demonstrating components of human skills such as active listening, empathy, and sympathy. These working systems support the prediction that a computer can begin to undo some of the negative feelings it causes by helping a user manage his or her emotional state. This paper clarifies the philosophy of this new approach to human–computer interaction: deliberately recognising and responding to an individual user's emotions in ways, that help users meet their needs. We define user needs in a broader perspective than has been hitherto discussed in the HCI community, to include emotional and social needs, and examine technology's emerging capability to address and support such needs. We raise and discuss potential concerns and objections regarding this technology, and describe several opportunities for future work.

Using a deliberately slow computer–game-interface to induce a state of hypothesised frustration in users, we collected physiological, video and behavioural data, and developed a strategy for coupling these data with real-world events. The effectiveness of our strategy was tested in a study with thirty six subjects, where the system was shown to reliably synchronise and gather data for affect analysis. A pattern-recognition strategy known as Hidden Markov Models was applied to each subject's physiological signals of skin conductivity and blood volume pressure in an effort to see if regimes of likely frustration could be automatically discriminated from regimes when frustration was much less likely. This pattern-recognition approach performed significantly better than random guessing at classifying the two regimes. Mouse-clicking behaviour was also synchronised to frustration-eliciting events and analysed, revealing four distinct patterns of clicking responses. We provide recommendations and guidelines for using physiology as a dependent measure for HCI experiments, especially when considering human emotions in the HCI equation.

The design of software for learners must be guided by educational theory. We present a framework for learner-centered design (LCD) that is theoretically motivated by sociocultural and constructivist theories of learning. LCD guides the design of software in order to support the unique needs of learners: growth, diversity, and motivation. To address these needs, we incorporate scaffolding into the context, tasks, tools, and interface of software learning environments. We demonstrate the application of our methodology by presenting two case studies of LCD in practice.