Publications

@mastersthesis{Agvik2015,

title = {A deformable terrain model in multi-domain dynamics using elastoplastic constraints: An adaptive approach},

author = {Simon Agvik},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-108328

http://umu.diva-portal.org/smash/get/diva2:852371/FULLTEXT01.pdf},

year  = {2015},

date = {2015-01-01},

school = {Department of Physics, Umeå University},

abstract = {Achieving realistic simulations of terrain vehicles in their work environment does not only require a careful model of the vehicle itself but the vehicle's interactions with the surroundings are equally important. For off-road ground vehicles the terrain will heavily affect the behaviour of the vehicle and thus puts great demands on the terrain model.



The purpose of this project has been to develop and evaluate a deformable terrain model, meant to be used in real-time simulations with multi-body dynamics. The proposed approach is a modification of an existing elastoplastic model based on linear elasticity theory and a capped Drucker-Prager model, using it in an adaptive way. The original model can be seen as a system of rigid bodies connected by elastoplastic constraints, representing the terrain. This project investigates if it is possible to create dynamic bodies just when it is absolutely necessary, and store information about possible deformations in a grid.



Two methods used for transferring information between the dynamic bodies and the grid have been evaluated; an interpolating approach and a discrete approach. The test results indicate that the interpolating approach is preferable, with better stability to an equal performance cost. However, stability problems still exist that have to be solved if the model should be useful in a commercial product.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Pettersson2015,

title = {Analysis and implementation of the Smooth Discrete Element Method in AGX},

author = {Thomas Pettersson},

editor = {Thomas Pettersson},

url = {http://liu.diva-portal.org/smash/get/diva2:856766/FULLTEXT02.pdf

http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aliu%3Adiva-121563},

year  = {2015},

date = {2015-01-01},

school = {Faculty of Science & Engineering, Linköping University},

abstract = {We encounter granular materials on a daily basis. We walk up a gravel path or we eat our breakfast cereals. When handling granular materials on an industrial scale it is important to do so efficiently, to avoid unnecessary energy losses, wear and tear. To help designing efficient tools for handling these materials engineers uses numerical simulations.



This project investigates the difference between the two main approaches to simulation of granular materials, the Smooth- and Non-smooth Discrete Element Methods by implementing the Smooth method into AgX dynamics were the Non-smooth method already is implemented, and then setup and execute a range of experiments to investigate their differences.



The investigation shows both advantages and weaknesses for both methods. The result of simulations with smooth discrete element method are more consistent than with the nonsmooth discrete element method with respect to choice of time step and other parameters that can be chosen for the simulation. Smooth discrete element method have problems when it comes to extreme situations.



The relative simulation time for system as large as treated by this project (more than1000) can not be shown to depend on the size of the system.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Sandqvist2015,

title = {Collision detection using boundary representation, BREP},

author = {Jonas Sandqvist},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-102531

http://umu.diva-portal.org/smash/get/diva2:808317/FULLTEXT01.pdf

},

year  = {2015},

date = {2015-01-01},

school = {Department of Physics, Umeå University},

abstract = {This thesis treats how to generate collision information for multibody simulations in AgX Dynamicswhere the geometries are described with the data structure boundary representation, BREP. BREP is adata structure that contains the exact mathematical description of each individual surface. To describecomplex surfaces exact and efficient non uniform rational basis spline, NURBS, is used and for trivialsurfaces like planes or spheres simpler equations is used. Since all surfaces in a BREP is described veryaccurate, the accuracy for the collision information can be set high without affecting the amount of dataneeded to describe the geometries.To make AgX Dynamics able to calculate forces in a multibody simulation, collision informationabout were and how much two geometries are intersecting is required. The collision information containswere the overlap between two geometries is, how much the objects have penetrated each other and thedirection for which the objects have to separate. To find the penetration depth and the overlap theNewton Raphson method were used. The experiments conducted, showed that it is possible to useBREPs as a description of geometries to produce the collision information needed for the physics engineused by AgX Dynamics to handle collisions. A comparison between trimesh and BREP for producingthe collision information, shows that data usage is much lower for the representation of geometries withBREPs than trimesh. The results also shows that the accuracy can be significantly higher than fortrimesh as the data usage for trimesh becomes non practical to handle when the required accuracy ishigh. With the high accuracy and with the smooth surfaces used with the BREP the artificial friction isalmost negligible except for cases were intersection points could not be found all around the intersectioncurves due to limitations in the algorithm.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{ostman2014collision,

title = {Collision detection for trimming curves and BREPs},

author = {Alexander Östman},

url = {http://umu.diva-portal.org/smash/record.jsf?searchId=2&pid=diva2:718124

http://umu.diva-portal.org/smash/get/diva2:718124/FULLTEXT01.pdf},

year  = {2014},

date = {2014-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {This report treats the implementation of collision detection algorithms for Boundary representations (BREPs) consisting of connected trimmed surfaces, mainly Non Uniform Rational Basis Spline (NURBS) surfaces. Using the OpenNurbs software package, complicated geometries created in CAD program Space Claim were imported to the physics engine AgX, where dynamic simulations were carried out. Collision detection algorithms for the geometry pairs BREP-line, BREP-plane and BREP-sphere have been developed and investigated. In the case of BREP-sphere collision detection, experiments have been carried out which show that BREP-shape representation exceeds trimesh-shape representation both in computational performance and in collision accuracy. The conclusion is that BREP representation has the potential to replace trimesh representation for some complex geometries with higher computational performance and more accurate simulations as a result.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Sandberg2014,

title = {Interactive simulation of hydrodynamics for arbitrarily shaped objects},

author = {Sandra Ålstig Sandberg},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-90060

http://umu.diva-portal.org/smash/get/diva2:725897/FULLTEXT02.pdf},

year  = {2014},

date = {2014-01-01},

school = {Department of Physics, Umeå University},

abstract = {Simulating hydrodynamics can require extensive calculations which becomes a problem when doing interactive simulations. This thesis investigates an efficient method for hydrodynamic simulations with the effects of buoyancy, drag, lift and added mass that is implementedand tested with the help of AgX Dynamics using triangulated meshes.



For buoyancy, drag and lift a method of numerical integration over triangles was used to calculate the forces and torques acting on each triangle of a mesh. For added mass a large part of the calculations could be done before the simulation starts using a Boundary Element Method (BEM). The final value for the added mass was calculated each time step based on how the object was submerged.



The method of triangle integration produced results that were close to the analytical values with a certain mesh dependence. The results had an increasing accuracy when the mesh had a more exact representation of the object. The drag and lift coefficients could however be better adjusted. The added mass results also had a mesh dependence, but with accuracy increasing with number of triangles even for shapes that already had an exact representation, e.g. a cube. For a fully submerged sphere with 4900 triangles the maximum error for the added mass was 0.65%.



The time required for precalculations using BEM had a rapid growth with increasing number of triangles due to the factorization of a dense matrix that has a complexity of O(n3). For the hydrodynamic calculations done each time step the time requirement increased linearly with number of triangles.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Ronnbäck2014,

title = {Parallel implementation of the projected Gauss-Seidel method on the Intel Xeon Phi processor – Application to granular matter simulation},

author = {Emil Rönnbäck},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-93299

http://umu.diva-portal.org/smash/get/diva2:747201/FULLTEXT01.pdf},

year  = {2014},

date = {2014-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {Being able to simulate granular matter is important, because they are ubiquitous both in nature and in industry. Some examples of granular materials are ore, sand, coffee, rice, corn, and snow. Research and development of new, more accurate, and faster methods to simulate even more complex materials with millions of particles are needed. In the work of this thesis a typical scene containing thousands of particles has been used for analysing simulation performance using the iterative Gauss-Seidel method adapted to the specifications and capabilities of the Intel Xeon Phi coprocessor. The work began with analysing the performance (wall-clock time and speedup) of a method developed by Algoryx Simulation. The work continued with finding the parts in the code causing bottlenecks and implementing improvements such as a distributed task scheduler and vectorization of operations. In the end, this resulted in shorter execution time and linear speedup using more than 40 threads, compared to 20 in the initial state. We also investigated the benefit of other techniques, such as cache prefetching and usage of huge page sizes, but found no performance gain from these. It is well known that the Xeon Phi coprocessor performs well when executing highly parallel applications, but overload may occur if excessive amount of data is requested by many threads simultaneously. To tackle this issue, the convergence rate of the Gauss-Seidel method during simulation has been measured and suggested modifications of the method decreasing data flow have been implemented and analysed.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Sundberg2014,

title = {Parallel projected Gauss-Seidelsolver for large-scale granular matter: Examining the physics of the parallel solver and development of a multigrid solver},

author = {Johan Sundberg},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-85831

http://www.diva-portal.org/smash/get/diva2:695410/FULLTEXT01.pdf

},

year  = {2014},

date = {2014-01-01},

school = {Department of Physics, Umeå University},

abstract = {Granular matter is found everywhere in nature and some examples include sand, rice,coee beans and iron ore pellets. Many dierent methods exists for simulating granularmatters using computers. In the scope of this thesis a physics engine called AgX Dynamicsfrom Algoryx Simulation AB is used to investigate and further develop methodsinvolving the discrete element method. During the rst half of 2013 a parallel solverfor the projected Gauss-Seidel method was implemented in AgX in order to speed upthe simulation time of simulations involving granular materials. In this thesis projectit is shown that the behaviour of the physics of this parallel solver is identical to theserial solver. Secondly this thesis works on the development of a multigrid solver forthe Gauss-Seidel method. Multigrid in this context means that the particle systemis partitioned in space. Each partition is then merged into a rigid body and contactforces between these rigid bodies is solved to machine precision using a direct solver.The forces from this direct solve is then used when solving the internal part of thepartitions using an iterative projected Gauss-Seidel method. The motivation for developinga multigrid method is to achieve faster convergence and even more speed-upof the solver. Numerical experiments has been performed on a 1D column and a 3Dsilo. The results show high potential of the method and the one-dimensional columnbehaves closer to a direct solver than an iterative solver. The thesis was done for UMIT Research Lab, Umea University and Algoryx Simulation AB.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Lindberg2014,

title = {Remote rendering of physics simulations and scalability aspects  in web applications},

author = {Lars Lindberg},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-90042

https://umu.diva-portal.org/smash/get/diva2:725806/FULLTEXT01.pdf},

year  = {2014},

date = {2014-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {This thesis, assigned by Algoryx Simulation AB, explores the concept of implementing a web application for managing Algoryx based physics simulations. The application enables users to get access to the Algoryx simulation software by providing a user interface for clients to submit scenes files to be simulated, and to view a 3D visualization of the finished simulations rendered directly in the web browser. This allows clients to do away with the work of performing the compute intensive physic simulations locally and instead hand over that responsibility to the web service, while the client only needs to handle the actual rendering. Applications made available through a web browser allows users to get easy access to applications that does not require any installation procedures. For that reason the clients do not need any simulation software or any plugin installed to access the service. This makes it easy to share results of simulations to customers by just giving out a link that can be accessed through a browser. 



This paper also includes a theoretical study on scalability in web applications. The theory explains different ways of scaling, and common techniques and methods used to help achieving scalability that can be useful when designing and building scalable web system.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Häggström2013,

title = {Collision detection with NURBS},

author = {Martin Häggström},

year  = {2013},

date = {2013-02-26},

school = {Department of Computing Science, Umeå University, Sweden},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Carlquist2013,

title = {Evaluation of Teaching Evolution Using Evolutionary Algorithms in a 2D Physics Sandbox},

author = {Joel Carlquist},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-80639

https://www.diva-portal.org/smash/get/diva2:650569/FULLTEXT01.pdf

},

year  = {2013},

date = {2013-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {Evolution and Darwin’s theory is the most important scientific theories for understanding human genealogy and our heritage. However, the theory of evolution has been continuously challenged and denied, without conclusive evidence against it. To show both the possibilities and power of evolution we are able to use evolutionary algorithms, a method used in computing science that is inspired by evolution. This is shown possible by developing and analysing a tool created for the 2D physics sandbox Algodoo. The tool uses evolutionary algorithms for improving objects. This tool is evaluated in two parts, a user survey and an analysis of the results of the evolution, where both indicate that while the tool does not quite reach the goals set, with further development the requirements will be met. The thesis also contains an overview of evolutionary algorithms and methods used in these, especially the methods used by Karl Sims in his work on evolved creatures. His work has been a great inspiration to this thesis.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{widlund_application2012,

title = {Application Programming Interface for Native Web Applications},

author = {Tobias Widlund},

url = {http://ltu.diva-portal.org/smash/record.jsf?pid=diva2%3A1020022&dswid=-73

http://ltu.diva-portal.org/smash/get/diva2:1020022/FULLTEXT02.pdf

},

year  = {2012},

date = {2012-06-21},

school = {Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology },

abstract = {This report describes a project about designing and implementing a usable application programming interface [API] for an existing application that was being ported to a web platform.



Today we experience a shift in how we humans work with computers in the sense that everything becomes more and more web oriented. To stay usable, software has to adapt to this and this project is an example on how such adaption may be performed.



The application, called Algodoo is an interactive 2D physics simulator written in C++ and as this was ported to the web using Native Client [NaCl] , it required new functionality to allow web page elements to interact with it. In other words, an API. It is the design and implementation of this API that is the focus of this report, but within it, the background for the project, will also be explained.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{berglund2012ice,

title = {Ice fracture model for real-time shipsimulator},

author = {Tomas Berglund},

url = {http://umu.diva-portal.org/smash/record.jsf?searchId=7&pid=diva2:586946

https://www.youtube.com/watch?v=-RCzkgP1cDw&ab_channel=Algoryx

http://umu.diva-portal.org/smash/get/diva2:586946/FULLTEXT01.pdf},

year  = {2012},

date = {2012-01-01},

school = {Department of Physics, Umeå University},

abstract = {Navigating in the arctic has become more common, but it is dificult and dangerous due to the presence of ice. Any training under safer circumstances is therefore very valuable, enter the need for ship simulators. Ship simulators today incorporate many features, such as cranes, anchors, wires, and state of the art physics. However, the inclusion of ice is very rare due to the complexity of simulating the feedback from the ice breaking progress.The purpose of this project is to build a model and numerical methods to simulate icefracture in real-time, which is to be used in ship simulators. The model presented inthis project is implemented with the use of the physics engine AgX Dynamics made by Algoryx Simulation AB. The method represents the ice sheet as a non-homogeneous mesh. A collision with thehull of the ship injects deformation energy into the ice. The energy from the inelasticimpact is distributed on the ice sheet according to a quasi-static crack propagationmodel that is dened on a static mesh. The cracks are guided using stress elds thatapproximate the strain in each vertex. The distribution of the strain is done by a simple model which allows for breaking ice in non-uniform fragments. This is more realistic than fracture in predened shapes which is the main contribution of this project. The fragments become unbreakable rigid body ice oes that interact with the ship’s hull by collision and friction. The implementation of the ice model is tested by using a trimesh model of the TorViking II icebreaker using approximated buoyancy calculations, damping equations, and engine forces. Real-time performance is not achieved yet in the general case, but this is due to the choice of collision geometry and the oe creation. Unstable force spikes from the contacts between the ship and the ice is detected, but the overall global ice resistance shows few abnormalities. Replacing the collision geometry and the rigid body oes isnecessary for the implementation to be able to run in real-time. Further experiments to compare with real model data is needed to be able to validate the model.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{Eriksson2012,

title = {Migrating Real-time Applications to the Web Browser},

author = {Benjamin Eriksson},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-80304

https://www.diva-portal.org/smash/get/diva2:648491/FULLTEXT01.pdf},

year  = {2012},

date = {2012-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {Today the web browser get a more central role in the arsenal of programs users use and at the same time installing programs is a bit of the past and every type of applications gets a web alternative. Users sees this as a good thing, however software companies which have put a lot of time, effort and money into their products might not be as happy in this platform paradigm shift.



The question is though, does it need to be a paradigm shift? Or is it possible to move an old application into this new, Operating System (OS) and architecture agnostic, multi purpose system the web has developed into?



This thesis tries to summarize which techniques there are, how they work, what their strengths and weaknesses are. As a bonus it also contains an independent case study of how it is to use the technology Native Client (NaCl) in alarge scale project.



The conclusion, from the case study, is that NaCl is a very promising technology both for migrating old code and for creating high performance code for this new platform. Our tests shows a 12:9% speed up when we using the 64 bitNaCl version over the native x86 32 bit version of Algodoo.



However, even though the technology seems mature the Software Development Kit (SDK) aren't which might be reason enough to idle for a while.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{dahlberg2011electricity,

title = {Electricity in a 2D mechanics simulator for education},

author = {Emanuel Dahlberg},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-40615

http://umu.diva-portal.org/smash/get/diva2:401366/FULLTEXT01.pdf},

year  = {2011},

date = {2011-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {Electricity can be a difficult topic to grasp since it is abstract, it is e.g. not possible to see the current and the voltage in a circuit. If electricity can be simulated and visualized, it can become less abstract and easier to understand. This thesis covers the process of simulating electricity in real-time together with a mechanics simulator, called Algodoo.



The process of analyzing electric circuits from a computers point of view is covered as well as different ways of simulating electric motors, generators and lasers. A large part of the thesis covers how to integrate the electricity and the mechanics simulators in a stable and accurate way. Furthermore, making the objects of the mechanics simulator able to conduct electricity is also covered. 



The thesis shows that it is possible to simulate electricity in real-time, and that physically correct conducting objects requires a lot of processing power, but can be simplified without losing too much correctness. The thesis also shows that the electrical and mechanics simulators preferably should be solved together to get a stable simulation.



Simulating electricity opens up an endless number of interactive scenarios, e.g. mechanical switches, potentiometers, relays and even logic gates. It can be a helpful aid as an introduction to electronics and since the simulators are integrated, it can also provide an introduction to mechanical work. The amount of energy required to perform dierent tasks can be compared and analyzed.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{sterner2011applications,

title = {Applications of Advanced Physics in Visual Effects},

author = {Tor Sterner Johansson},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-48329

http://umu.diva-portal.org/smash/get/diva2:448459/FULLTEXT01.pdf},

year  = {2011},

date = {2011-01-01},

school = {Department of Computing Science, Umeå University},

abstract = {AgX Multiphysics is a toolkit for performing physics-based simulations, developed by Algoryx Simulations AB. AgX provides stable physics simulations and is used for industrial and engineering simulations around the world.This thesis examines the possibilities for AgX to be used in the visual effects market for films and commercials. The thesis includes a survey of opinions of professionals from the visual effects company Digital Domain. The three most wanted capabilities from AgX was according to the survey; stiff constraints, fluid-rigid body interaction and hair simulation. Furthermore, all new tools must improve or be equal on all aspects compared to the old tools, and have good scalability.Several simulations were run to compare the stiff constraints and scalability of AgX with the currently used tools. The results show that AgX handles stiff constraints a lot better than the old tool and is also highly scalable.In summary, for saving time from doing tedius tasks and for using physics to an extent earlier not possible, AgX would be a good addition to the current use of physics in visual effects.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{backman2011collision,

title = {Collision Detection of TriangleMeshes Using GPU},

author = {Nils Bäckman},

url = {http://urn.kb.se/resolve?urn=urn%3Anbn%3Ase%3Aumu%3Adiva-40912

http://umu.diva-portal.org/smash/get/diva2:403566/FULLTEXT01.pdf},

year  = {2011},

date = {2011-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {Collision detection in physics engines often use primitives such as spheres and boxes since collisions between these objects are straightforward to compute. More complicated objects can then be modeled using compounds of these simpler primitives.

However, in the pursuit of making it easier to construct and simulate complicated objects, triangle meshes are a good alternative since it is usually the format used by modeling tools.

This thesis demonstrates how triangle meshes can be used directly as collision objects within a physics engine. The collision detection is done using triangle mesh models with tests accelerated using a tree-based bounding volume hierarchy structure.

OpenCL is a new open industry framework for writing programs on heterogeneous platforms, including highly parallel platforms such as Graphics Processing Units(GPUs).

Through the use of OpenCL, parallelization of triangle mesh collision detection is implemented for the GPU, then evaluated and compared to the CPU implementation.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{wan2011discrete,

title = {Discrete element method in granular material simulations},

author = {Yijun Wan},

url = {https://pure.tue.nl/ws/portalfiles/portal/47015912/716753-1.pdf},

year  = {2011},

date = {2011-01-01},

journal = {Institute of Fraunhofer ITWM Kaiserslautern/Technical University of Kaiserslautern},

abstract = {This thesis describes the theories and simulations of granular material using discrete element method. With wide applications in agriculture and mechanical engineering, granular material exhibits a number of unique physical properties. The understanding of such properties is important in order to evaluate the performance of existing methodologies and to trigger the development of new models for different functionalities in the future. As a microscopic approach, discrete element method has been proved to be adequate in most simulations of granular material. An elaborated description is provided to illustrate a three-phase scheme from the fundamental discrete element model, which includes contact detection, force interaction and time integration. Additional to the conventional scheme, we present a bonding model with a connecting rod between each pair of contacted particles. Two enhanced bonding models are discussed in detail, with special characteristics in accordance with brittle and crack propagation features, respectively. On the contrary, continuum mechanical models give a macroscopic view to investigate granular material behaviors. Difficulties arise from the solving of a complex system of partial differential equations and the connections between model parameters and phenomenological ones. Moreover, triaxial test, uniaxial compression test and blade test are chosen as three representative experiments in granular material study. Simulation results implementing discrete element method are analyzed and discussed regarding the role of different parameters. By carefully choosing models and adjusting parameters, simulation results can have a good quantitative agreement with laboratory measurements. One of our kernel concerns is the computational complexity. Therefore, we focus on exploring effective simplified models with fewer variables.},

keywords = {External},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{gunnarsson2010robot,

title = {Robot Design Optimization by means of a Genetic Algorithm and Physics Simulation},

author = {Morgan Gunnarsson},

url = {http://umu.diva-portal.org/smash/record.jsf?pid=diva2%3A375435&dswid=-7990

http://umu.diva-portal.org/smash/get/diva2:375435/FULLTEXT01.pdf},

year  = {2010},

date = {2010-01-01},

abstract = {This thesis presents a new robot design paradigm that utilizes evolutionary optimization techniques and advanced physics simulations. This technology makes it possible to design and test robots in virtual environments before the physical robots are built, which enables robot manufacturers to improve the performance of their products and decrease the time and cost for development. In this project, a 3D robot model was defined in geometric, kinematic and dynamic terms. Also, a piece of software was developed in C++ to optimize the robot design, and to simulate and visualize the robot model with the aid of a physics engine. A genetic algorithm was developed for the optimization and used to minimize the average positional error and the total torque magnitude under constraints on speed, and the design variables were the PID controller parameters and the torque actuator limits. Only predefined robots can be programmed and simulated with current software packages for offline-programming and robot simulation. It was concluded that such software packages can be improved by robot design optimization using the software developed in this project, by means of a genetic algorithm and simulations using a physics engine.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{sundholm2010distance,

title = {Distance Fields Accelerated with OpenCL},

author = {Erik Sundholm},

url = {http://umu.diva-portal.org/smash/record.jsf?pid=diva2:327072

http://umu.diva-portal.org/smash/get/diva2:327072/FULLTEXT01.pdf},

year  = {2010},

date = {2010-01-01},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {An important task in any graphical simulation is the collision detection between the objects in the simulation. It is desirable to have a good general method for collision detection with high performance. This thesis describes an implementation of a collision detection method that uses distance fields to detect collisions. This method is quite robust and able to detect collisions between most possible shapes. It is also capable of computing contact data for collisions. A problem with distance fields is that the performance cost for making a distance field is quite extensive. It is therefore customary to have some way of accelerating the computation of the distance field (usually by only computing select parts of the field). The application implemented in this thesis solves this performance problem by using the parallel framework OpenCL for accelerating the construction of the field.OpenCL enables programmers to execute code on the GPU. The GPU is highly data parallel and a huge increase in performance can be obtained by letting the GPU handle the computations associated with the initiation of the field.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}

@mastersthesis{nilsson2009constraint,

title = {Constraint Fluids on GPU},

author = {Martin Nilsson},

url = {http://www8.cs.umu.se/education/examina/Rapporter/MartinNilsson.pdf

https://www.algoryx.se/mainpage/wp-content/uploads/2021/04/MartinNilsson.pdf

https://www.youtube.com/watch?v=0e3p5iu3zj8&t=1s&ab_channel=Algoryx},

year  = {2009},

date = {2009-01-01},

publisher = {Citeseer},

school = {Department of Computing Science, Umeå University, Sweden},

abstract = {The processing power of graphics hardware has increased tremendously in the last several years and they are therefore used more and more outside of their intended domain of graphics rendering. This thesis describes the implementation and results of a fluid simulator, using the constraint fluid method, which harnesses the processing power of modern GPUs, in particular NVIDIA’s CUDA platform. As demonstrated in this thesis, particle systems with hundreds of thousands of particles can be simulated and visualized at interactive rates and systems containing up to a million particles can be run at a few frames per second. The biggest performance bottleneck is currently in the solver, in particular the lack of a working preconditioned Conjugate Gradient implementation.},

keywords = {Algoryx},

pubstate = {published},

tppubtype = {mastersthesis}

}