SIGGRAPH Asia 2022 Papers

We present a novel Monte Carlo-based fluid simulation approach capable of pointwise and stochastic estimation of fluid motion. Drawing on the Feynman-Kac representation of the vorticity transport equation, we propose a recursive Monte Carlo estimator of the Biot-Savart law and extend it with a stream function formulation that allows us to treat free-slip boundary conditions using a Walk-on-Spheres algorithm. Inspired by the Monte Carlo literature in rendering, we design and compare variance reduction schemes suited to a fluid simulation context for the first time, show its applicability to complex boundary settings, and detail a simple and practical implementation with temporal grid caching. We validate the correctness of our approach via quantitative and qualitative evaluations - across a range of settings and domain geometries - and thoroughly explore its parameters' design space. Finally, we provide an in-depth discussion of several axes of future work building on this new numerical simulation modality.

In this work, we present a high frame rate affordable nystagmus detection aid for outpatient clinic use. Using a Frenzel goggles and the high-speed video recording feature of a smartphone, high-frame rate eye videos of patients are obtained. Then, OpenCV morphological operation and blob detection library were modified to manually adjust the parameters according to the video to capture and track the eye center movements. Next, we correct the error caused by hand shaking during photography and predict the eyeball movement during blinking. Finally, with rule-based detecting method, nystagmus was detected and classified based on the modified tracking data. In our experimental, we collaborated with a professional ENT doctor to obtain multiple high-frame rate eye videos of patients. Experimental results show that this procedure can provide preliminary diagnosis results for physicians to refer to, but the final diagnosis needs to be made by a professional ophthalmologist. Plus, this method has been used by the ENT doctor to record the result simultaneously.

Hair rendering has been a focal point of attention in computer graphics for the last couple of decades. However, there have been few contributions to the modeling and rendering of the natural hair aging phenomenon. We present a new technique that simulates the process of hair graying and hair thinning on digital models due to aging. Given a 3D human head model with hair, we first compute a segmentation of the head using K-means since hair aging occurs at different rates in distinct head parts. Hair graying is simulated according to recent biological knowledge on aging factors for hairs, and hair thinning decreases hair diameters linearly with time. Our system is biologically inspired, supports facial hair, both genders and many ethnicities, and is compatible with different lengths of hair strands. Our real-time results resemble real-life hair aging, accomplished by simulating the stochastic nature of the process and the gradual decrease of melanin.

Since the development of 3D applications, the point cloud, as a spatial description easily acquired by sensors, has been widely used in multiple areas such as SLAM and 3D reconstruction. Point Cloud Compression (PCC) has also attracted more attention as a primary step before point cloud transferring and saving, where the geometry compression is an important component of PCC to compress the points geometrical structures. However, existing non-learning-based geometry compression methods are often limited by manually pre-defined compression rules. Though learning-based compression methods can significantly improve the algorithm performances by learning compression rules from data, they still have some defects. Voxel-based compression networks introduce precision errors due to the voxelized operations, while point-based methods may have relatively weak robustness and are mainly designed for sparse point clouds. In this work, we propose a novel learning-based point cloud compression framework named 3D Point Cloud Geometry Quantiation Compression Network (3QNet), which overcomes the robustness limitation of existing point-based methods and can handle dense points. By learning a codebook including common structural features from simple and sparse shapes, 3QNet can efficiently deal with multiple kinds of point clouds. According to experiments on object models, indoor scenes, and outdoor scans, 3QNet can achieve better compression performances than many representative methods.