Real-time Realistic Rain Rendering

Artistic outdoor filming and rendering need to choose specific weather conditions in order to properly trigger the audience reaction; for instance, rain, one of the most common conditions, is usually employed to transmit a sense of unrest. Synthetic methods to recreate weather are an important avenue to simplify and cheapen filming, but simulations are a challenging problem due to the variety of different phenomena that need to be computed. Rain alone involves raindrops, splashes on the ground, fog, clouds, lightnings, etc. We propose a new rain rendering algorithm that uses and extends present state of the art approaches in this field. The scope of our method is to achieve real-time renders of rain streaks and splashes on the ground, while considering complex illumination effects and allowing an artistic direction for the drops placement. Our algorithm takes as input an artist-defined rain distribution and density, and then creates particles in the scene following these indications. No restrictions are imposed on the dimensions of the rain area, thus direct rendering approaches could rapidly overwhelm current computational capabilities with huge particle amounts. To solve this situation, we propose techniques that, in rendering time, adaptively sample the particles generated in order to only select the ones in the regions that really need to be simulated and rendered. Particle simulation is executed entirely in the graphics hardware. The algorithm proceeds by placing the particles in their updated coordinates. It then checks whether a particle is falling as a rain streak, it has reached the ground and it is a splash or, finally, if it should be discarded because it has entered a solid object of the scene. Different rendering techniques are used for each case. Complex illumination parameters are computed for rain streaks to select textures matching them. These textures are generated in a preprocess step and realistically simulate light when interacting with the optical properties of the water drops

Fast Collision Culling in Large-Scale Environments Using GPU Mapping Function

International audienceThis paper presents a novel and efficient GPU-based parallel algorithm to cull non-colliding object pairs in very large-scale dynamic simulations. It allows to cull objects in less than 25ms with more than 100K objects. It is designed for many-core GPU and fully exploits multi-threaded capabilities and data-parallelism. In order to take advantage of the high number of cores, a new mapping function is defined that enables GPU threads to determine the objects pair to compute without any global memory access. These new optimized GPU kernel functions use the thread indexes and turn them into a unique pair of objects to test. A square root approximation technique is used based on Newton's estimation, enabling the threads to only perform a few atomic operations. A first characterization of the approximation errors is presented, enabling the fixing of incorrect computations. The I/O GPU streams are optimized using binary masks. The implementation and evaluation is made on largescale dynamic rigid body simulations. The increase in speed is highlighted over other recently proposed CPU and GPU-based techniques. The comparison shows that our system is, in most cases, faster than previous approaches

Fast GPU-Based Two-Way Continuous Collision Handling

Step-and-project is a popular way to simulate non-penetrated deformable bodies in physically-based animation. First integrating the system in time regardless of contacts and post resolving potential intersections practically strike a good balance between plausibility and efficiency. However, existing methods could be defective and unsafe when the time step is large, taking risks of failures or demands of repetitive collision testing and resolving that severely degrade performance. In this paper, we propose a novel two-way method for fast and reliable continuous collision handling. Our method launches the optimization at both ends of the intermediate time-integrated state and the previous intersection-free state, progressively generating a piecewise-linear path and finally reaching a feasible solution for the next time step. Technically, our method interleaves between a forward step and a backward step at a low cost, until the result is conditionally converged. Due to a set of unified volume-based contact constraints, our method can flexibly and reliably handle a variety of codimensional deformable bodies, including volumetric bodies, cloth, hair and sand. The experiments show that our method is safe, robust, physically faithful and numerically efficient, especially suitable for large deformations or large time steps

Optimization techniques for a 2D Engine

This document contains the description of the development of a small 2D engine written in C++. The focus of this project is to implement various optimization techniques to have a performant application. The result is a small 2D engine that can be executed in any Windows machine and can handle more than 10.000 entities interacting with each other in real time. The source code for this project is public and under the MIT License and can be found in the Github repository in the following link: https://github.com/DavidTello1/2D-Rendere

Real-time Realistic Rain Rendering

Artistic outdoor filming and rendering need to choose specific weather conditions in order to properly trigger the audience reaction; for instance, rain, one of the most common conditions, is usually employed to transmit a sense of unrest. Synthetic methods to recreate weather are an important avenue to simplify and cheapen filming, but simulations are a challenging problem due to the variety of different phenomena that need to be computed. Rain alone involves raindrops, splashes on the ground, fog, clouds, lightnings, etc. We propose a new rain rendering algorithm that uses and extends present state of the art approaches in this field. The scope of our method is to achieve real-time renders of rain streaks and splashes on the ground, while considering complex illumination effects and allowing an artistic direction for the drops placement. Our algorithm takes as input an artist-defined rain distribution and density, and then creates particles in the scene following these indications. No restrictions are imposed on the dimensions of the rain area, thus direct rendering approaches could rapidly overwhelm current computational capabilities with huge particle amounts. To solve this situation, we propose techniques that, in rendering time, adaptively sample the particles generated in order to only select the ones in the regions that really need to be simulated and rendered. Particle simulation is executed entirely in the graphics hardware. The algorithm proceeds by placing the particles in their updated coordinates. It then checks whether a particle is falling as a rain streak, it has reached the ground and it is a splash or, finally, if it should be discarded because it has entered a solid object of the scene. Different rendering techniques are used for each case. Complex illumination parameters are computed for rain streaks to select textures matching them. These textures are generated in a preprocess step and realistically simulate light when interacting with the optical properties of the water drops

A Framework for Dynamic Terrain with Application in Off-road Ground Vehicle Simulations

The dissertation develops a framework for the visualization of dynamic terrains for use in interactive real-time 3D systems. Terrain visualization techniques may be classified as either static or dynamic. Static terrain solutions simulate rigid surface types exclusively; whereas dynamic solutions can also represent non-rigid surfaces. Systems that employ a static terrain approach lack realism due to their rigid nature. Disregarding the accurate representation of terrain surface interaction is rationalized because of the inherent difficulties associated with providing runtime dynamism. Nonetheless, dynamic terrain systems are a more correct solution because they allow the terrain database to be modified at run-time for the purpose of deforming the surface. Many established techniques in terrain visualization rely on invalid assumptions and weak computational models that hinder the use of dynamic terrain. Moreover, many existing techniques do not exploit the capabilities offered by current computer hardware. In this research, we present a component framework for terrain visualization that is useful in research, entertainment, and simulation systems. In addition, we present a novel method for deforming the terrain that can be used in real-time, interactive systems. The development of a component framework unifies disparate works under a single architecture. The high-level nature of the framework makes it flexible and adaptable for developing a variety of systems, independent of the static or dynamic nature of the solution. Currently, there are only a handful of documented deformation techniques and, in particular, none make explicit use of graphics hardware. The approach developed by this research offloads extra work to the graphics processing unit; in an effort to alleviate the overhead associated with deforming the terrain. Off-road ground vehicle simulation is used as an application domain to demonstrate the practical nature of the framework and the deformation technique. In order to realistically simulate terrain surface interactivity with the vehicle, the solution balances visual fidelity and speed. Accurately depicting terrain surface interactivity in off-road ground vehicle simulations improves visual realism; thereby, increasing the significance and worth of the application. Systems in academia, government, and commercial institutes can make use of the research findings to achieve the real-time display of interactive terrain surfaces

Position Based Balloon Angioplasty

Balloon angioplasty is an endovascular procedure to widen narrowed or obstructed blood vessels, typically to treat arterial atherosclerosis. Simulating angioplasty procedure in the complex vascular structures is a challenge task since the balloon and vessels are both flexible bodies. In this paper, we proposed a position based balloon physical model to solve nonlinear physical deformation in the process of balloon inflation. Firstly, the balloon is discrete modeled by the closed triangle mesh, and the hyperelastic membrane material and continuum based formulation are combined to compute the mechanical properties in the process of balloon inflation. Then, an adaptive air mesh generation algorithm is proposed as a preprocessing procedure for accelerating the coming collision process between balloon and blood vessel according to the characteristic of collision area which is relative fixed. The experiment results show that this physical model is feasible, which could simulate the contact and deformation process between the inflation balloon and the diseased blood vessel wall with good robustness and in realtime