EG2024

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https://diglib.eg.org/handle/10.2312/3606947

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Real-time Seamless Object Space Shading
(The Eurographics Association, 2024) Li, Tianyu; Guo, Xiaoxin; Hu, Ruizhen; Charalambous, Panayiotis
Object space shading remains a challenging problem in real-time rendering due to runtime overhead and object parameterization limitations. While the recently developed algorithm by Baker et al. [BJ22] enables high-performance real-time object space shading, it still suffers from seam artifacts. In this paper, we introduce an innovative object space shading system leveraging a virtualized per-halfedge texturing schema to obviate excessive shading and preclude texture seam artifacts. Moreover, we implement ReSTIR GI on our system (see Figure 1), removing the necessity of temporally reprojecting shading samples and improving the convergence of areas of disocclusion. Our system yields superior results in terms of both efficiency and visual fidelity.
StarDEM: Efficient Discrete Element Method for Star-shaped Particles
(The Eurographics Association, 2024) Schreck, Camille; Lefebvre, Sylvain; Jourdan, David; Martínez, Jonàs; Hu, Ruizhen; Charalambous, Panayiotis
Granular materials composed of particles with complex shapes are challenging to simulate due to the high number of collisions between the particles. In this context, star shapes are promising: they cover a wide range of geometries from convex to concave and have interesting geometric properties. We propose an efficient method to simulate a large number of identical star-shaped particles. Our method relies on an effective approximation of the contacts between particles that can handle complex shapes, including highly non-convex ones. We demonstrate our method by implementing it in a 2D simulation using the Discrete Element Method, both on the CPU and GPU.
Modern Dance Retargeting using Ribbons as Lines of Action
(The Eurographics Association, 2024) Vialle, Manon; Ronfard, Rémi; Skouras, Melina; Hu, Ruizhen; Charalambous, Panayiotis
We present a method for retargetting dancing characters represented as articulated skeletons with possibly different morphologies and topologies. Our approach relies on the use of flexible ribbons that can bend and twist as an intermediate representation, and that can be seen as animated lines of action. These ribbons allow us to abstract away the specific morphology of the bodies and to well transmit the fluidity of modern dance movement from one character to another.
A Generative Approach to Light Placement for Street Lighting
(The Eurographics Association, 2024) Evangelou, Iordanis; Vitsas, Nick; Papaioannou, Georgios; Gkaravelis, Anastasios; Hu, Ruizhen; Charalambous, Panayiotis
The design of plausible and effective street lighting configurations for arbitrary urban sites should attain predetermined illuminance levels and adhere to specific layout intentions and functional requirements. This task can be time consuming, even for automated solutions, since there exists an one-to-many mapping between illumination goals and lighting options. In this work, we propose a generative approach for this task, based on an adversarial optimisation scheme. Our proposed method effectively overcomes these task-specific limitations by providing a range of viable solutions that adhere to the input constraints and can be generated within an interactive design life cycle.
Efficient and Accurate Multi-Instance Point Cloud Registration with Iterative Main Cluster Detection
(The Eurographics Association, 2024) Yu, Zhiyuan; Zheng, Qin; Zhu, Chenyang; Xu, Kai; Hu, Ruizhen; Charalambous, Panayiotis
Multi-instance point cloud registration is the problem of recovering the poses of all instances of a model point cloud in a scene point cloud. A traditional solution first extracts correspondences and then clusters the correspondences into different instances. We propose an efficient and robust method which clusters the correspondences in an iterative manner. In each iteration, our method first computes the spatial compatibility matrix between the correspondences, and detects its main cluster. The main cluster indicates a potential occurrence of an instance, and we estimate the pose of this instance with the correspondences in the main cluster. Afterwards, the correspondences are removed to further register new instances in the following iterations. With this simplistic design, our method can adaptively determine the number of instances, achieving significant improvements on both efficiency and accuracy.
Utilizing Motion Matching with Deep Reinforcement Learning for Target Location Tasks
(The Eurographics Association, 2024) Lee, Jeongmin; Kwon, Taesoo; Shin, Hyunju; Lee, Yoonsang; Hu, Ruizhen; Charalambous, Panayiotis
We present an approach using deep reinforcement learning (DRL) to directly generate motion matching queries for longterm tasks, particularly targeting the reaching of specific locations. By integrating motion matching and DRL, our method demonstrates the rapid learning of policies for target location tasks within minutes on a standard desktop, employing a simple reward design. Additionally, we propose a unique hit reward and obstacle curriculum scheme to enhance policy learning in environments with moving obstacles.
SPnet: Estimating Garment Sewing Patterns from a Single Image of a Posed User
(The Eurographics Association, 2024) Lim, Seungchan; Kim, Sumin; Lee, Sung-Hee; Hu, Ruizhen; Charalambous, Panayiotis
This paper presents a novel method for reconstructing 3D garment models from a single image of a posed user. Previous studies that have primarily focused on accurately reconstructing garment geometries to match the input garment image may often result in unnatural-looking garments when deformed for new poses. To overcome this limitation, our work takes a different approach by inferring the fundamental shape of the garment through sewing patterns from a single image, rather than directly reconstructing 3D garments. Our method consists of two stages. Firstly, given a single image of a posed user, it predicts the garment image worn on a T-pose, representing the baseline form of the garment. Then, it estimates the sewing pattern parameters based on the T-pose garment image. By simulating the stitching and draping of the sewing pattern using physics simulation, we can generate 3D garments that can adaptively deform to arbitrary poses. The effectiveness of our method is validated through ablation studies on the major components and a comparison with other methods.
Skeleton-Aware Skin Weight Transfer for Helper Joint Rigs
(The Eurographics Association, 2024) Cao, Ziyuan; Mukai, Tomohiko; Hu, Ruizhen; Charalambous, Panayiotis
We propose a method to transfer skin weights and helper joints from a reference model to other targets. Our approach uses two types of spatial proximity to find the correspondence between the target vertex and reference mesh regions. The proposed method first generates a guide weight map to establish a relationship between the skin vertices and skeletal joints using a standard skinning technique. The correspondence between the reference and target skins is established using vertex-to-bone projection and bone-to-skin ray-casting using the guide weights. This method enables fully automated and smooth transfer of skin weight between human-like characters bound to helper joint rigs.
An Inverse Procedural Modeling Pipeline for Stylized Brush Stroke Rendering
(The Eurographics Association, 2024) Li, Hao; Guan, Zhongyue; Wang, Zeyu; Hu, Ruizhen; Charalambous, Panayiotis
Stylized brush strokes are crucial for digital artists to create drawings that express a desired artistic style. To obtain the ideal brush, artists need to spend much time manually tuning parameters and creating customized brushes, which hinders the completion, redrawing, or modification of digital drawings. This paper proposes an inverse procedural modeling pipeline for predicting brush parameters and rendering stylized strokes given a single sample drawing. Our pipeline involves patch segmentation as a preprocessing step, parameter prediction based on deep learning, and brush generation using a procedural rendering engine. Our method enhances the overall experience of digital drawing recreation by empowering artists with more intuitive control and consistent brush effects.
Design and development of VR games for Cultural Heritage using Immersive Storytelling
(The Eurographics Association, 2024) Rizvic, Selma; Mijatovic, Bojan; Mania, Katerina; Artusi, Alessandro
In this tutorial we introduce the whole process of creating, designing and developing a serious VR game for cultural heritage using the concept of immersive storytelling. The use of serious games in education is allowing us to offer a different approach to learning. However, designing an application with gameplay parts as well as educational components in specific area such as cultural heritage can be challenging and different to many other methodologies in the creation of similar applications. The goal of the tutorial is to show different aspects of serious game creation and usage of our immersive storytelling methodology called hyper storytelling to help with the educational elements of the game. We will go through the creation of a story for the game; the creation of scenarios for the educational gameplay part; the filming of actors on green screen and filming of 360 videos; compositing of VR videos with actors and ambisonic sound; the creation of photogrammetry items; combining educational parts with gameplay and creating connection between them; application development and finalization of the product. At the end, we will showcase our example of the game.
A Highly Adaptable and Flexible Rendering Engine by Minimum API Bindings
(The Eurographics Association, 2024) Kim, Taejoon; Hu, Ruizhen; Charalambous, Panayiotis
This paper presents a method for embedding a rendering engine into different development environments with minimal API bindings. The method separates the engine interfaces into two levels: System APIs and User APIs. System APIs are the lowlevel functions that enable communication between the engine and the user environment, while User APIs are the high-level functions that provide rendering and beyond rendering functionalities to the user. By minimizing the number of System APIs, the method simplifies the adaptation of the engine to various languages and platforms. Its applicability and flexibility are demonstrated by the successful embedding the engine in multiple environments, including C/C++, C#, Python, Javascript, and Matlab. It also demonstrates its versatility in diverse forms such as CLI renderers, Web GUI framework-based renderers, remote renderers, physical simulations, and more, while also enabling the easy adoption of other rendering algorithms to the engine.
Next Generation 3D Face Models
(The Eurographics Association, 2024) Chandran, Prashanth; Yang, Lingchen; Mania, Katerina; Artusi, Alessandro
Having a compact, expressive and artist friendly way to represent and manipulate human faces has been of prime interest to the visual effects community for the past several decades as face models play a very important role in many face capture workflows. In this short course, we go over the evolution of 3D face models used to model and animate facial identity and expression in the computer graphics community, and discuss how the recent emergence of deep face models is transforming this landscape by enabling new artistic choices. In this first installment, the course will take the audience through the evolution of face models, starting with simple blendshape models introduced in the 1980s; that continue to be extremely popular today, to recent deep shape models that utilize neural networks to represent and manipulate face shapes in an artist friendly fashion. As the course is meant to be beginner friendly, the course will commence with a quick introduction to non-neural parametric shape models starting with linear blendshape and morphable models. We will then switch focus to deep shape models, particularly those that offer intuitive control to artists. We will discuss multiple variants of such deep face models that i) allow semantic control, ii) are agnostic to the underlying topology of the manipulated shape, iii) provide the ability to explicitly model a sequence of 3D shapes or animations, and iv) allow for the simulation of physical effects. Applications that will be discussed include face shape synthesis, identity and expression interpolation, rig generation, performance retargeting, animation synthesis and more.
FACTS: Facial Animation Creation using the Transfer of Styles
(The Eurographics Association, 2024) Saunders, Jack R.; Namboodiri, Vinay P.; Hu, Ruizhen; Charalambous, Panayiotis
The ability to accurately capture and express emotions is a critical aspect of creating believable characters in video games and other forms of entertainment. Traditionally, this animation has been achieved with artistic effort or performance capture, both requiring costs in time and labor. More recently, audio-driven models have seen success, however, these often lack expressiveness in areas not correlated to the audio signal. In this paper, we present a novel approach to facial animation by taking existing animations and allowing for the modification of style characteristics. We maintain the lip-sync of the animations with this method thanks to the use of a novel viseme-preserving loss. We perform quantitative and qualitative experiments to demonstrate the effectiveness of our work.
DeepIron: Predicting Unwarped Garment Texture from a Single Image
(The Eurographics Association, 2024) Kwon, Hyun-Song; Lee, Sung-Hee; Hu, Ruizhen; Charalambous, Panayiotis
Realistic reconstruction of 3D clothing from an image has wide applications, such as avatar creation and virtual try-on. This paper presents a novel framework that reconstructs the texture map for 3D garments from a single garment image with pose. Since 3D garments are effectively modeled by stitching 2D garment sewing patterns, our specific goal is to generate a texture image for the sewing patterns. A key component of our framework, the Texture Unwarper, infers the original texture image from the input garment image, which exhibits warping and occlusion of the garment due to the user's body shape and pose. This is effectively achieved by translating between the input and output images by mapping the latent spaces of the two images. By inferring the unwarped original texture of the input garment, our method helps reconstruct 3D garment models that can show high-quality texture images realistically deformed for new poses. We validate the effectiveness of our approach through a comparison with other methods and ablation studies.
Neural Moment Transparency
(The Eurographics Association, 2024) Tsopouridis, Grigoris; Vasilakis, Andreas Alexandros; Fudos, Ioannis; Hu, Ruizhen; Charalambous, Panayiotis
We have developed a machine learning approach to efficiently compute per-fragment transmittance, using transmittance composed and accumulated with moment statistics, on a fragment shader. Our approach excels in achieving superior visual accuracy for computing order-independent transparency (OIT) in scenes with high depth complexity when compared to prior art.
Predictive Modeling of Material Appearance: From the Drawing Board to Interdisciplinary Applications
(The Eurographics Association, 2024) Baranoski, Gladimir V. G.; Mania, Katerina; Artusi, Alessandro
This tutorial addresses one of the fundamental and timely topics of computer graphics research, namely the predictive modeling of material appearance. Although this topic is deeply rooted in traditional areas like rendering and natural phenomena simulation, this tutorial is not limited to cover contents connected to these areas. It also closely looks into the scientific methodology employed in the development of predictive models of light and matter interactions. Given the widespread use of this methodology to find modeling solutions for problems within and outside computer graphics, its discussion from a ''behind the scenes'' perspective aims to underscore practical and far-reaching aspects of interdisciplinary research that are often overlooked in related publications. More specifically, this tutorial unveils constraints and pitfalls found in each of the key stages of the model development process, namely data collection, design and evaluation, and brings forward alternatives to tackle them effectively. Furthermore, besides being a central component of realistic image synthesis frameworks, predictive material appearance models have a scope of applications that can be extended far beyond the generation of believable images. For instance, they can be employed to accelerate the hypothesis generation and validation cycles of research across a wide range of fields, from biology and medicine to photonics and remote sensing, among others. These models can also be used to generate comprehensive in silico (computational) datasets to support the translation of knowledge advances in those fields to real-world applications (e.g., the noninvasive screening of medical conditions and the remote detection of environmental hazards). In fact, a number of them are already being used in physical and life sciences, notably to support investigations seeking to strengthen the current understanding about material appearance changes prompted by mechanisms which cannot be fully studied using standard ''wet'' experimental procedures. Accordingly, such interdisciplinary research initiatives are also discussed in this tutorial through selected case studies involving the use of predictive material appearance models to elucidate challenging scientific questions.
EUROGRAPHICS 2024: Short Papers Frontmatter
(Eurographics Association, 2024) Hu, Ruizhen; Charalambous, Panayiotis; Hu, Ruizhen; Charalambous, Panayiotis
Accurate Boundary Condition for Moving Least Squares Material Point Method using Augmented Grid Points
(The Eurographics Association, 2024) Toyota, Riku; Umetani, Nobuyuki; Hu, Ruizhen; Charalambous, Panayiotis
This paper introduces an accurate boundary-handling method for the moving least squares (MLS) material point method (MPM), which is a popular scheme for robustly simulating deformable objects and fluids using a hybrid of particle and grid representations coupled via MLS interpolation. Despite its versatility with different materials, traditional MPM suffers from undesirable artifacts around wall boundaries, for example, particles pass through the walls and accumulate. To address these issues, we present a technique inspired by a line handler for MLS-based image manipulation. Specifically, we augment the grid by adding points along the wall boundary to numerically compute the integration of the MLS weight. These additional points act as background grid points, improving the accuracy of the MLS interpolation around the boundary, albeit with a marginal increase in computational cost. In particular, our technique makes the velocity perpendicular to the wall nearly zero, preventing particles from passing through the wall. We compare the boundary behavior of 2D simulation against that of naïve approach.
EUROGRAPHICS 2024: Tutorials Frontmatter
(Eurographics Association, 2024) Mania, Katerina; Artusi, Alessandro; Mania, Katerina; Artusi, Alessandro
Fast Dynamic Facial Wrinkles
(The Eurographics Association, 2024) Weiss, Sebastian; Chandran, Prashanth; Zoss, Gaspard; Bradley, Derek; Hu, Ruizhen; Charalambous, Panayiotis
We present a new method to animate the dynamic motion of skin micro wrinkles under facial expression deformation. Since wrinkles are formed as a reservoir of skin for stretching, our model only deforms wrinkles that are perpendicular to the stress axis. Specifically, those wrinkles become wider and shallower when stretched, and deeper and narrower when compressed. In contrast to previous methods that attempted to modify the neutral wrinkle displacement map, our approach is to modify the way wrinkles are constructed in the displacement map. To this end, we build upon a previous synthetic wrinkle generator that allows us to control the width and depth of individual wrinkles when generated on a per-frame basis. Furthermore, since constructing a displacement map per frame of animation is costly, we present a fast approximation approach using pre-computed displacement maps of wrinkles binned by stretch direction, which can be blended interactively in a shader. We compare both our high quality and fast methods with previous techniques for wrinkle animation and demonstrate that our work retains more realistic details.

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