Deep 3D morphable models (deep 3DMMs) play an essential role in computer vision. They are used in facial synthesis, compression, reconstruction and animation, avatar creation, virtual try-on, facial recognition systems and medical imaging. These applications require high spatial and perceptual quality of synthesised meshes. Despite their significance, these models have not been compared with different mesh representations and evaluated jointly with point-wise distance and perceptual metrics. We compare the influence of different mesh representation features to various deep 3DMMs on spatial and perceptual fidelity of the reconstructed meshes. This paper proves the hypothesis that building deep 3DMMs from meshes represented with global representations leads to lower spatial reconstruction error measured with L 1 and L 2 norm metrics and underperforms on perceptual metrics. In contrast, using differential mesh representations which describe differential surface properties yields lower perceptual FMPD and DAME and higher spatial fidelity error. The influence of mesh feature normalisation and standardisation is also compared and analysed from perceptual and spatial fidelity perspectives. The results presented in this paper provide guidance in selecting mesh representations to build deep 3DMMs accordingly to spatial and perceptual quality objectives and propose combinations of mesh representations and deep 3DMMs which improve either perceptual or spatial fidelity of existing methods.

Abstract A novel unified particle‐based method is proposed for real‐time dissolution simulation that is fast, predictable, independent of sampling resolution, and visually plausible. The dissolution model is derived from collision theory and integrated into a smoothed particle hydrodynamics fluid solver. Dissolution occurs when a solute is submerged in solvent. Physical laws govern the local excitation of solute particles based on kinetic energy: when the local excitation energy exceeds a user‐specified threshold (activation energy), the particle will be dislodged from the solid. Solute separation during dissolution is handled using a new Graphics Processing Unit (GPU)‐based region growing method. The use of smoothed particle hydrodynamics sampling for both solute and solvent guarantees a predictable and smooth dissolution process and provides user control of the volume change during the phase transition. A mathematical relationship between the activation energy and dissolution time allows for intuitive artistic control over the global dissolution rate. We demonstrate this method using a number of practical examples, including antacid pills dissolving in water, hydraulic erosion of nonhomogeneous terrains, and melting.

We propose a novel algorithm for blue noise sampling inspired by the Smoothed Particle Hydrodynamics (SPH) method. SPH is a well-known method in fluid simulation -- it computes particle distributions to minimize the internal pressure variance. We found that this results in sample points (i.e., particles) with a high quality blue-noise spectrum. Inspired by this, we tailor the SPH method for blue noise sampling. Our method achieves fast sampling in general dimensions for both surfaces and volumes. By varying a single parameter our method can generate a variety of blue noise samples with different distribution properties, ranging from Lloyd's relaxation to Capacity Constrained Voronoi Tessellations (CCVT). Our method is fast and supports adaptive sampling and multi-class sampling. We have also performed experimental studies of the SPH kernel and its influence on the distribution properties of samples. We demonstrate with examples that our method can generate a variety of controllable blue noise sample patterns, suitable for applications such as image stippling and re-meshing.

We propose an energy-based method for dissolution simulation. Both the fluid (solvent) and solid (solute) are presented by particles. The dissolution priority of solute particles is based on the kinetic activation energy. The position of solute is determined using rigid body dynamics. We demonstrate plausible dissolving behaviours by using examples.

This paper describes the impact of display resolution and luminance on the responses of participants in a behavioral study that used a projection-based Immersive Virtual Reality System. The scenario was a virtual bar where participants witnessed a violent attack of one person on another due to an argument about support for a soccer club. The major response variable was the number of interventions made by participants. The study was between-groups with 10 participants in two groups pre-upgrade and post-upgrade, both in the same 4-screen Cave-like system. However, the post-upgrade group experienced the scenario with projectors that had a significantly higher level of resolution and luminance than those experienced by the pre-upgrade group. The results show that, other things being equal, the number of both verbal and physical interventions was greater amongst those in the post-upgrade group compared to the pre-upgrade group.

Bipedal walking is not fully understood. Motion generated from methods employed in robotics literature is stiff and is not nearly as energy efficient as what we observe in nature. In this paper, we propose validity conditions for motion adaptation from biological principles in terms of the topology of the dynamic system. This allows us to provide a closed-form solution to the problem of motion adaptation to environmental perturbations. We define both global and local controllers that improve structural and state stability, respectively. Global control is achieved by coupling the dynamic system with a neural oscillator, which preserves the periodic structure of the motion primitive and ensures stability by entrainment. A group action derived from Lie group symmetry is introduced as a local control that transforms the underlying state space while preserving certain motor invariants. We verify our method by evaluating the stability and energy consumption of a synthetic passive dynamic walker and compare this with motion data of a real walker. We also demonstrate that our method can be applied to a variety of systems.

A least-squares mesh is a surface representation consisting of a small set of anchor points and the differential and topological properties of the surface. In this paper, we present a novel method to identify motion-sensitive anchor points for least-squares meshes from a set of examples. We present a new method, called clustered teleconnection analysis, to identify the maximally excited points in a subset of basis vectors deduced using principal component analysis. We demonstrate by means of examples that our approach has a smaller reconstruction error and equivalent performance to the current best approaches.

Abstract Skin sliding is the phenomenon of the skin moving over underlying layers of fat, muscle and bone. Due to the complex interconnections between these separate layers and their differing elasticity properties, it is difficult to model and expensive to compute. We present a novel method to simulate this phenomenon at real‐time by remeshing the surface based on a parameter space resampling. In order to evaluate the surface parametrization, we borrow a technique from structural engineering known as the force density method (FDM)which solves for an energy minimizing form with a sparse linear system. Our method creates a realistic approximation of skin sliding in real‐time, reducing texture distortions in the region of the deformation. In addition it is flexible, simple to use, and can be incorporated into any animation pipeline. Copyright © 2009 John Wiley & Sons, Ltd.

Abstract Continuity in level of detail sequences is essential in hiding visual artefacts that occur when switching between discrete levels of detail. However, construction and implementation of these sequences is prohibitively complex. We present a new structure, the g‐mesh, which greatly simplifies the implementation of continuous level of detail in large scenes. We also introduce a novel greedy predictive level of detail control system suited to the g‐mesh. Finally we achieve a dramatic improvement in the rendering of morphing sequences by exploiting current graphics hardware. ACM CSS:I.3.5 Computational Geometry and Object Modeling—Geometric Transformations, Object Hierarchies, I.3.6 Methodology and Techniques—Graphics Data Structures