111 research outputs found
APPLICATION OF VARIATIONAL CALCULUS IN THE RADIOSITY METHOD
The original radiosity method searches for the radiosity distribution in a piecewise constant
function form. Using this stepwise constant assumption about the radiosity distribution,
the integral equation describing the energy transfer is transformed to a linear equation
system. Higher order radiosity method means the approximation of the radiosity distri-
bution by more complex functions, as for example, by piecewise linear, harmonic, wavelet,
etc. function series with unknown coefficients. Due to higher order approximation, the
number of the unknown variables can be significantly smaller than the number of constant
steps in the original method. This paper discusses the conversion of the integral equation
to an equivalent variational problem which can result in a linear equation system for the
unknown coefficients. Three function bases are examined in detail in this framework:
piecewise constant, piecewise linear and harmonic approximations
Virtuális világok szimuláciĂłja Ă©s megjelenĂtĂ©se = Simulation-Rendering in Virtual Reality Systems
1. A Navier-Stokes egyenletek Lagrange-i Ă©s Euler-i nĂ©zĹ‘pontjának masszĂvan párhuzamos architektĂşrán vĂ©grehajthatĂł hatĂ©kony megoldási algoritmusa folyadĂ©kszimuláciĂłhoz. A folyadĂ©k szabályozása, azaz elĹ‘Ărt sűrűsĂ©gfĂĽggvĂ©ny felĂ© terelĂ©se. 2. Formális nyelvek, L-rendszerek párhuzamos kiĂ©rtĂ©kelĂ©si algoritmusa Ă©s alkalmazás ""vĂ©gtelen"" városok Ă©s növĂ©nyek szimuláciĂłjára. 3. TĂ©rfogati modellekben a fĂ©nyterjedĂ©s szimuláciĂł szabad Ăşthossz mintavĂ©telezĂ©sĂ©nek hatĂ©kony megoldása, amely heterogĂ©n közegben extrĂ©m nagy felbontásokra (pl. 32 ezer köbös) is működik. 4. TĂ©rfogati modellek vĂ©ges elemes megoldásához az iteráciĂłt gyorsĂtĂł kezdeti becslĹ‘ kialakĂtása. 5. A fotonterjedĂ©s szimuláciĂłjának felhasználása inverz feladatokban, pozitron emissziĂłs tomográfiához rekonstrukciĂłs eljárások kidolgozása. 6. A Koksma-Hlawka egyenlĹ‘tlensĂ©g általánosĂtása nem egyenletes minták esetĂ©re Ă©s ez alapján delta-szigma moduláciĂłs mĂłdszer kidolgozása fontosság szerinti mintavĂ©telezĂ©shez. 7. Az ambiens takarási mĂłdszer Ăşj geometriai Ă©rtelmezĂ©sĂ©nek megalkotása Ă©s Ăşj, hatĂ©kony mĂłdszerek kidolgozása. 8. Out-of-core vizualizáciĂł sugárkövetĂ©s alapon, több száz milliĂł háromszögbĹ‘l állĂł modellek interaktĂv bejárása. 9. Az NPR algoritmusoknál a 3D konzisztencia biztosĂtása, Ă©s animáciĂłs algoritmusok lĂ©trehozása. | 1. Algorithms for the solution of the Navier-Stokes equations of fluids on massively parallel hardware, taking both the Eulerian and Lagrangian viewpoints. Solution of the fluid control problem. 2. Parallel evaluation of L-systems and its application to procedural infinite virtual worlds. 3. Free path sampling method for high resolution, heterogeneous participating media. 4. Bootstrapping the iterative solver of finite element approaches for light transport in participating media. 5. Development of a parallel solver for the photon transport problem and its application in positron emission tomography. 6. Generalization of Koksma-Hlawka inequality and the development of a delta-sigma type importance sampling. 7. New geometric interpretation for ambient occlusion and novel computation algorithms. 8. Out-of-core visualization methods based on ray tracing. 9. Solution of the 3D consistency problem of NPR and extension to animation sequences
Go with the winners strategy in path tracing
This paper proposes a new random walk strategy that minimizes the variance of the estimate
using statistical estimations of local and global features of the scene. Based on the local and
global properties, the algorithm decides at each point whether a Russian-roulette like random
termination is worth performing, or on the contrary, we should split the path into several child
paths. In this sense the algorithm is similar to the go-with-the-winners strategy invented in general
Monte Carlo context. However, instead of establishing thresholds to make decisions, we compute
the number of child paths on a continuous level and show that Russian roulette can be interpreted
as a kind of splitting using fractional number of children. The new method is built into a path
tracing algorithm, and a minimum cost heuristic is proposed for choosing the number of rejected
rays. Comparing it with the classical path tracing approach we concluded that the new method
reduced the variance significantly
Comparison of Non-Linear Filtering Methods for Positron Emission Tomography
As a result of the limited radiotracer dose, acquisition time and scanner sensitivity, positron emission tomography (PET) images suffer from high noise. In the current clinical practice, post-reconstruction filtering has become one of the most common noise reduction techniques. However, the range of existing filters is very wide, and choosing the most suitable filter for a given measurement is far from simple. This paper aims to provide assistance in this choice by comparing the most powerful image denoising filters, covering both image quality and execution time. Emphasis is placed on non-linear techniques due to their ability to preserve edges and fine details more accurately than linear filters. The compared methods include the Gaussian, the bilateral, the guided, the anisotropic diffusion and the non-local means filters, which are examined in both static and dynamic PET reconstructions
InteraktĂv globális illumináciĂł = Interactive global illumination
1. SugárkövetĂ©s alapĂş mĂłdszerek 1.1. Fontosság szerinti mintavĂ©telezĂ©s A többszörös fontosság szerinti mintavĂ©telezĂ©s kĂĽlönbözĹ‘ stochasztikus iteráciĂłs eljárások elĹ‘nyeinek az egyesĂtĂ©sĂ©re. SĂşlyozott fontosságszerinti mintavĂ©tel Ă©s a Metropolis mĂłdszer. 1.2. A fĂ©nyutak ĂşjrahasznosĂtása FĂ©nyĂşt minták megtartása. Ezen a terĂĽleten a láthatĂłság számĂtást sikerĂĽlt egy közelĂtĹ‘ mĂłdszerrel felgyorsĂtani. Az interaktĂv rendszerekben illetve az animáciĂłban az idĹ‘beli koherenciát is sikerĂĽlt kiaknázni. 1.3. A "Go with the winners" elvű mĂłdszer alkalmazásának kidolgozása 1.4. A fontosság szerinti mintavĂ©telezĂ©st a korrelált mintavĂ©telezĂ©ssel sikerĂĽlt kombinálni. 2. Grafikus hardver alapĂş megoldások Ezen a terĂĽleten a következĹ‘ algoritmusokat dolgoztuk ki: 2.1. Randomizált radiozitás a GPU-n 2.2. FĂ©nyanimáciĂł, amikor a szĂntĂ©r statikus, de a fĂ©nyforrások Ă©s a kamera szabadon mozoghatnak 2.3. Égbolt fĂ©nyforrások hatásának valĂłs idejű számĂtása 2.4. Fák, erdĹ‘k interaktĂv megjelenĂtĂ©se. 2.5. Egyszeres Ă©s többszörös tĂĽkrözĹ‘ Ă©s törĹ‘ felĂĽletek 2.6. Kausztikus jelensĂ©gek 2.7. DiffĂşz Ă©s csillanĂł interreflexiĂłk 2.8. A Fresnel kĂ©pleteknek egy olyan egyszerűsĂtĂ©se, amely komplex törĂ©smutatĂłjĂş anyagok esetĂ©n is jĂł 2.9 FĂ©nyelnyelĹ‘ anyagok plakát vágási hibáktĂłl mentes megjelenĂtĂ©se 2.10 FĂ©nyelnyelĹ‘ anyagokban a többszörös szĂłrĂłdás | 1. CPU ray-tracing 1.1. Importance sampling Multiple importance sampling was used to combine different stochastic iteration algorithms. Weighted importance sampling was also exploited. We proposed Metropolis sampling for iteration, which was adapted to curve design as well. 1.2. Light path reuse Sampling method reusing partial light path samples, fast visibility algorithms and the exploitation of time coherence. 1.3. Adaptation of the 'Go with the winners' sampling method. 1.4. Combination of importance sampling with correlated sampling 2. Graphics hardware based methods: 2.1. Stochastic radiosity 2.2. Light animation in real-time 2.3. Image based lighting 2.4. Visualization of trees 2.5. Single and multiple reflections and refractions 2.6. Caustics 2.7. DiffĂşz Ă©s csillanĂł interreflexiĂłk 2.8. Fresnel approximations for metals 2.9 Participating media withouth billboard clipping artifacts 2.10 Multiple scattering in participating medi
Informatikai algoritmusok 2.
A könyv a Magyar Tudományos Akadémia támogatásával készül
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