


 Department of Computer Software 
 Computer Graphics Laboratory 

  
 Gennadiy Nikishkov Professor  Roman Durikovic Assistant Professor 


Computer Graphics Laboratory focuses on physics based modeling of different phenomena, their visualization and animation. New approaches to modeling, rendering, simulation and scientific visualization are developed. Created mathematical models are used for graphical representation of natural processes.
Current research areas include:
 Visualization of surface and volume data, which results from finite element, boundary element and finite difference modeling.
 Development of augmenter reality interface suitable for use in medical physics measurements. In augmented reality, computer generated visual information is combined with real world video.
 Nano mechanics modeling. Numerical approach is used for modeling of micro and nanostructures with large translations and rotations.
 Adaptive surface and volume approximation. Special quadtree/octree finite element technique is developed for surface on surface or function in volume approximation.
 Physicsbased animation of liquids and bubbles, and hair dynamics.
 Hardware based rendering. Modification of rendering equation to simulate different effects on GPU in realtime.
 Photon mapping rendering techniques for dynamic scenes. We propose a novel approaches to use as much as possible the information from previous frames.
 Rendering the real paints. Construction of BRDF from paint composition and rendering with GPU. Examples include Japanese lacquer ware.
 Dynamics growth of organs. Function representation, formal languages and physical environment are combined to simulate different organs.
Professors of the Computer Graphics Laboratory deliver courses in Computer Graphics, Introduction to Topology, Language Processing, Numerical Analysis, Modeling and Visualization. Graduation projects and SCCP are related to computer modeling, visualization and animation and to Web technologies.



 [niki01:2003]  G.P.Nikishkov. Curvature estimation for multilayer hinged structures with initial strains. Journal of Applied Physics, 94(8):53335336, 2003.
Closedform estimate of curvature for hinged multilayer structures with initial strains is developed. The finite element method is used for modeling of self positioning microstructures. The geometrically nonlinear problem with large rotations and large displacements is solved using step procedure with node coordinate update. Finite element results for curvature of the hinged micromirror with variable width is compared to closedform estimates. 
 [niki02:2003]  G.P.Nikishkov, Yu.G.Nikishkov, and V.V.Savchenko. Comparison of C and Java performance in finite element computations. Computers and Structures, 81:24012408, 2003.
The Java programming language has several features, which make it attractive for software development in computational engineering and sciences. One major obstacle to use of Java incomputationally intensive applications is its reputation of a slowlanguage in comparison to Fortran or C. In this paper the performance of the developed Java finite element code is compared to that of the C code on the solution of threedimensional elasticity problems. It is shown that simple code tuning can provide Java/C performance ratio 90element equations. The PCG iterative solution algorithm is 1.5 times slower using the Java tuned code in comparison to theCcode.WerecommendusingJVM1.2 since in many cases it is considerably faster in finite element computations than JVMs 1.3 and 1.4. 
 [niki03:2003]  G.P.Nikishkov. Generating contours on FEM/BEM higherorder surfaces using Java 3D textures. Advances in Engineering Software, 34:469476, 2003.
An eAEcient technique to visualize primary and secondary results for combined FEM/BEMmodels as contours is presented. The technique is based on dividing higherorder surfaces into triangles and on using texture interpolation to produce contour plots. Since results of high accuracy with significant gradients can be obtained using sparse meshes of boundary elements and finite elements, special attention is devoted to element face subdivision. Subdivision density is defined on the basis of both face edge curvature and ranges of result fields over element faces. Java 3D API is employed for code development. 
 [niki04:2003]  G.P.Nikishkov, I.Khmyrova, and V.Ryzhii. Finite element analysis of selfpositioning microstructures and nanostructures. Nanotechnology, 14:820823, 2003.
The finite element method is used for modeling of selfpositioning micro and nanostructures. The geometrically nonlinear problem with large rotations and large displacements is solved using step procedure with coordinate updating after each step. It is shown that the real shape of selfpositioning structures is rather complicated and the analytical formulas have limited applicability in the estimate of such their parameters as curvature radius and/or angle of elevation. 
 [roman01:2003]  Ryou Kimura and R. Durikovic. RealTime rendering of Japanese lacquerware. Journal of Three Dimensional Images, 18(3):110115, dec 2004.
Japanese lacquerware has been used from long ago in Japanese daily life. Makie is a famous surface decoration technique using metallic powders, colorpigments, and lacquer. We propose a method for realtime rendering of Makie.The optical properties of the Makie surface is represented using Bidirectional Reflectance Distribution Function (BRDF). Sphere environment maps are generated for the realtime visualization of BRDFs. A photo of Makie designed on a flat surface is taken with a digital camera. Masking textures with alpha channels are made from the photo for blending sphere maps. Multipass texture blending is used for realtime visualization of Makie decoration on general PCs. 
 [roman02:2003]  R. Durikovic and S. Czanner. Modeling with three types of Coons bodies. International Journal of Modeling and Simulation, 24(2):97101, apr 2004.
This article discusses the mathematical concepts of multivariate parametric solids and their description by Bspline basis functions. Parametric solids can model both the shape and unisotropic interior. Three types of parametric solids, Coons body of types 0, 1, and 2, are used to demonstrate the interior modelling often used as initial or boundary conditions in numerical simulation. Multiple parametric solid elements can be joined together to form a complicated shape. Continuity between elements can be defined as in Bspline modelling. The proposed methodology and modelling technique is applied to a metamorphosis of two given 3D shapes. 

 Refereed Proceeding Papers 

 [niki05:2003]  G.P.Nikishkov. Modelling of selfpositioning micro/nanostructures. In Proceedings of the 1st Int. Conf. on Finite Elements for Process LUXFEM 2003, page 9 pp., Luxembourg, 1314 Nov. 2003.
The finite element procedure is developed for the solution of threedimensional geometrically nonlinear problems with small strains and large rotational and translational displacements. Updated Lagrangian formulation is used with controlling strains and stresses at local coordinate frames at element integration points. Equilibrium iterations at each step are performed according to the NewtonRaphson method. Hexahedral 20node elements are used for discretization. The developed finite element procedure is applied to modelling of selfpositioning micro and nanostructures. Amultilayer structure is formed with the molecular beam epitaxy method. Some layers have different lattice periods that leads to the structure selfpositioning after etchingouta sacrificial materiallayer.Incomputationalmodelling, etching of the sacrificial layer is simulated by release of displacement constraints or by specifying zero elasticitymodulus in elements of the sacricfiial layer. Results for a self positioning micromirror with a hinge of a variable width are compared to the closedform solutions for limiting cases of narrow and wide hinges. 
 [niki06:2003]  G.P.Nikishkov. Java performance in finite element computations. In Editor M.H.Hamza, editor, Proceedings of the 12th IASTED Int. Conf. on Applied Simulation and Modeling, pages 130135., Marbella, Spain, 35 Sept. 2003.
The performance of the developed Java finite element code is compared to that of the C finite element code on the solution of threedimensional elasticity problems using Intel Pentium 4 computer. Untuned Java code is approximately two times slower then analogousCcode. It is shown that code tuning with the use of blocking technique can provide Java/Cperformance ratio 90equations. Javaperformance for PCG iterative solution algorithm tuned by inner loop unrolling is 75recommended for code execution since in many cases it is considerably faster in finite element computations than JVMs 1.3 and 1.4. 
 [roman03:2003]  R. Durikovic andW. Martens. Simulation of sparkling and depth effect in paints. In K.I. Joyand L. SzirmayKalos, editors, ACMProceedings of the 19th Spring Conference on Computer Graphics  SCCG2003, pages 207213, Budmerice, Slovakia, apr 2003.
This paper reports on our attempts to simulate light reflection from surfaces that exhibit sparkling and depth effects that are associated with paint coatings containing metallic flakes. The novelty of the approach is to explicitly model the sparkle geometry for rendering the surface of a graphic object. The light scattering within the system of metal flakes or particles creates the sparkling and glare effects with radial streaks of light around high intensity particles. The 3D geometry of the simulated flakes creates a?iewdependent reflectance pattern that makes the surface appear differently in the two images rendered for each eye's view in a?tereoscopic display. The results of 3D geometrybased rendering are then compared to the surfaces rendered using 2D random dot patterns that provide no cues to depth variation at the surface. Stereoscopic display of 3D objects with and without the 3D geometrybased surface rendering was used to validate the difference in perceived depth effects associated with the two cases. To confirm the applicability of the technique, we adopted a standard test in common use by paint designers in which the appearance of paints with different sparkle density is observed on silver plates. Our results showedtypical variation in sparklingon plates with different statistical distributions of sparkles, which confirmed the robustness of the 3D sparkle modeling system. In a final application test, the technique was used to simulate the appearance of an expensive variety of Japanese lacquerware made using the nashiji technique. 
 [roman04:2003]  R. Durikovic, R. Kimura, and K. Kolchin. Realtime Visualization of Japanese artcraft. In IEEE Proceedings of the Computer Graphics International  CGI2003, pages 184189, Tokyo, Japan, jul 2003.
We present several methods for simulation of Japanese lacquer ware, a prominent Far East Asian handicraft art. We consider two most popular kinds of Japanese lacquerware made by the makie and nashiji techniques. For rendering makie, we propose a method for preparing RGBA textures from digital photos of art items. The alpha channels of these textures control the weight with which color channels are blended with the measured biderectional reffectance distribution function (BRDF) of a metallic finish. Both ray tracing and hardware based rendering are demonstrated. In the latter case, we show how the calculation of a sphere map texture used for BRDF visualization can be accelerated using a special coordinate system for tabulated BRDF. 
 [roman05:2003]  R. Durikovic. Towards visual modelling of bonsai trees. In Proceedings of the IASTED Visualization, Imaging, Image Processing  VIIP2003, pages 797802, Malaga, Spain, sep 2003.
In this paper we introduce a method for the modelling of trees with exactly given shape. This was not possible with previous methods because the Lsystem parameters were diAEcult to set in order to get the exact shape of a plant. With our method we can generatethe Lsystemgrammarswhich will generate the tree with requested silhouette easily. We demonstrate our method on modelling of bonsai trees. They have complex shape and the shape is the most important factor. We proposed the approach consisting of two novel ideas: generating the silhouette table resulting in the exact shape of trunk and main branches and distribution of small branches with leaves in next table according to a given density function. 
 [roman06:2003]  R.KimuraandR.Durikovic. Realtime renderingofJapanese lacquerware. InProceedings of theHumanandComputer Conference HC2003, pages 8994, AizuWakamatsu, Japan, sep 2003.
Japanese lacquerware has been used from long ago in Japanese daily life. Makie is a famous surface decoration technique using metallic powders, color pigments, and lacquer. We propose amethod for realtime rendering of Makie. The optical properties of the Makie surface is represented using Bidirectional Reflectance Distribution Function (BRDF). Sphere environment maps are generated for the realtime visualization of BRDFs. A photo of Makie designed on a flat surface is taken with a digital camera. Masking textures with alpha channels are made from the photo for blending spheremaps. Multipass texture blending is used for realtime visualization of Makie decoration on general PCs. 
 [roman07:2003]  S. Kinuwaki and R. Durikovic. Modeling thick pain on Japanese lacquerware. In Joint Convention Record of Tohoku Chapter of the IPSJ, pages 2326, No. A22, Koriyama, Japan, nov 2003.
Japanese lacquer is used in many objects such as table, chopstick, cup, trays and container. Lacquerware is woodencontainers with lacquer.Tree sap is used tomake clear raw lacquer. In making of lacquer, there are three steps. They are carving a container out of wood, coating it with ware, and drawing pictures on a surface. In the previous works, two stage methods for rendering were proposed. In the first stage, radiance sphere mapswere computed for each metallic powderand color pigment. We express lacquer ware(urushi) optical effects using BRDF(bidirectional reflectance distribution function) that is a function describing how the light propagates from incident to outgoing angle. In the second stage, they blended computed sphere maps and textures with controlled alpha channel. In this work, we focus mostly on second rendering stage. Recently, GPU rendering using programmable shader has been displacing prior fixed function pipeline. To get flexible extension, we propose a urushi rendering technique using programmable shader. Sphere coordinate is calculated on vertex shader, multi texture blending operation is done on pixel shader, and bumpy effect called bump mapping is added to the surface in pixel shader, too. 
 [roman08:2003]  P. Kianicka and R. Durikovic. Simulation of water dynamics effects using multiphaseflow approach. In A. Pasko, editor, Proceedings of the 20th Spring Conference on Computer Graphics  SCCG2004, pages 2930, Budmerice, Slovakia, apr 2004.
Presented method for modelling and animation of fluids is based on the numerical multiphaseflow solverdevelopedby JosStamandimproves a surface tension calculation. Interfaces between fluids are constructed by the marching cubes algorithm and simulation is rendered byPOVRay. 
 [roman09:2003]  A. Ciganek and R. Durikovic. Rigid body dynamics of implicit objects defined with Frep. In A. Pasko, editor, Proceedings of the 20th Spring Conference on Computer Graphics SCCG2004, page 31, Budmerice, Slovakia, apr 2004.
The functional representation and how it can be used for representing rigid bodies is presented. The concepts of rigid body dynamics, which depend on representation of bodies, are closely described. Method of collision detection of frep is presented. Finally, the problem of constrained dynamics is presented. 
 [roman10:2003]  P. JankuliakandR.Durikovic. Simulation ofrunningbullsduring Spanish fiesta. In A. Pasko, editor, Proceedings of the 20th Spring Conference on Computer Graphics  SCCG2004, page 32, Budmerice, Slovakia, apr 2004.
We will simulate running peoples from furious bulls during@@@@ 'fiesta' in Spain. Here autonomous agents will be both 'human' and @@@@ controlled by artificial intelligence. 


 [roman11:2003]  R. Durikovic and A. Belyaev. Proceedings of the Geometric Modeling, Computing, and Visualization. Technical Report 20031004, The University of Aizu, Japan, Jul 2003. 


 [roman12:2003]  D. Wei, S. Kazuhiro, R. Durikovi??c, M. Nobuhiko, and C. Vilbrandt. IT Text, Computer Graphics (in Japanese), pages 113・132,179・ 220. Ohmsa Press, Tokyo, Japan, dec 2003. 


 [roman13:2003]  R. Durikovic. Ministry of Education Scientific Research Fund, 20032004. 


 [niki07:2003]  Gennadiy Nikishkov, 2003.
International Journal 'Computer Modeling in Engineering and Sciences'. Member of the Editorial Board

 [niki08:2003]  Gennadiy Nikishkov, Sept. 2003.
Section Chair, the 12thIASTEDInt. Conference onApplied Simulation andModeling

 [roman14:2003]  Roman Durikovic, Apr. 2003.
Organizing Committee Member, ACMSCCG 2003 Conference.

 [roman15:2003]  Roman Durikovic, Jul. 2003.
Organizing Committee Member, EG and ACMGRAPHICON 2003 Conference.

 [roman16:2003]  Roman Durikovic, Nov. 2003.
Committee Member, EGWSCG 2003 Conference.

 [roman17:2003]  Roman Durikovic, Jul. 2003.
Committee Member, CGI 2003 Conference.br>



 [niki09:2003]  Youhei Nishidate. Graduation Thesis: Curve reconstruction using FEM, University of Aizu, 2003.
Thesis Advisor: Gennadiy Nikishkov

 [niki10:2003]  Masataka Noguchi. Graduation Thesis: Generation of 2D quadrilateral finite element mesh, University of Aizu, 2003.
Thesis Advisor: Gennadiy Nikishkov

 [niki11:2003]  Takeo Niitsuma. Graduation Thesis: Automatic generation of 3D finite element mesh, University of Aizu, 2003.
Thesis Advisor: Gennadiy Nikishkov

 [niki12:2003]  JunnosukeTorigoe. Graduation Thesis: Extraction of finite element isosurfaces, University of Aizu, 2003.
Thesis Advisor: Gennadiy Nikishkov

 [niki13:2003]  Yasufumi Suzuki. Contour plots of 2D finite element results, University of Aizu, 2003.
Thesis Advisor: Gennadiy Nikishkov

 [roman18:2003]  Hirotsugu Fujimagari. Graduation Thesis: The realtime toon shading algorithms., University of Aizu, 2003.
Thesis Advisor: Roman Durikovic.

 [roman19:2003]  Katsuhiro Numata. Graduation Thesis: Constraints in rigid dynamics, University of Aizu, 2003.
Thesis Advisor: Roman Durikovic.

 [roman20:2003]  Tomomi Sakuma. Graduation Thesis: Dynamics of soap bubble cluster, University of Aizu, 2003.
Thesis Advisor: Roman Durikovic.



 [roman21:2003]  R. Durikovic, March 2004.
Invited lecture at Max Plank Institute, Saarbrucken, Germany

 [roman22:2003]  R. Durikovic, December 2003.
Invited lecture at Graz Univerzity, Austria

 [roman23:2003]  R. Durikovic, December 2003.
Invited lecture at Comenius University, Slovak Republic

 [roman24:2003]  R. Durikovic, December 2003.
Invited lecture at University of saint Cyril and Method, Slovak Republic

