Rendering Techniques in 3D Computer Graphics Based on Changes in the Brightness of the Object Background

Maintaining accurate colour constancy and constant colour appearance are only a few challenges one must conquer in a modern day digital three‐dimensional (3D) production. Many different factors influence the reproduction of colour in 3D rendering and one of the most important is certainly rendering engines. In our research, we have studied rendering of colours with three rendering engines (Blender Render, Cycles and Yafaray) of an open source 3D creation suite based on changes in the brightness of the object background from 20 to 80%. In one of these cases, colour of the object was adapted to the lighter background using the colour appearance model CIECAM02. With the analysis of colour differences, lightness and chroma between colours rendered using different rendering engines; we found out that rendering engines differently interpret colour, although the RGB values of colours and scene parameters were the same. Differences were particularly evident when rendering engine Cycles was used. However, Cycles also takes into account the object background. Numerical results of such research provide findings, which relate to the respective environment, and also these certainly demonstrate the successful implementation of the colour appearance model CIECAM02 in the 3D technologies and, in our opinion to other software packages for 3D computer graphics

Colorimetric Accuracy of Color Reproductions in the 3D Scenes

Color is a complex phenomenon that depends on the object, the observer and the light source, while the color reproduction additionally includes the surrounding conditions and it depends on the device that can either capture, display or print the reproduction. Colour accuracy is very important for digital reproduction of artistic work where colour represents essence of art. In our research, color reproductions of renderings of computer generated scenes, including an object, background and lights were assessed, and even more, colorimetric accuracy in renderings was analyzed. With assumption that shading in 3D computer generated scenes plays an important role in visual perception of rendered color, the colors were analyzed on renderings of shaded objects. It was determined that colorimetric accuracy depends on the position on rendered objects, either illuminated or shaded. Furthermore, it was discovered that color lightness and hue, light intensity and background influenced ΔRGB values

Application of uniform color appearance model to color rendering in static three-dimensional computer-generated graphics

Kljub tehnološkemu napredku zadnjih stoletij in desetletij se še vedno soočamo s problematiko prikaza in upodobitve barve na različnih medijih ter ohranjanja zaznave barve. Ena izmed možnosti, po kateri lahko posežemo pri zagotavljanju konstantne barvne zaznave, so modeli barvnega zaznavanja. Trenutno je aktualen CIECAM02, ki ima sicer velik potencial, a v praksi še vedno ni uporabljen, tudi v povezavi s 3D računalniško grafiko, s katero se prav tako soočamo skoraj vsakodnevno. Namen disertacije je bil preučiti napredno barvno metriko in model barvnega zaznavanja CIECAM02 do te mere, da bi ga lahko uporabili v povezavi s 3D računalniško grafiko. Ob tem smo predpostavili, da bo CIECAM02 uporaben tudi v 3D prostoru. Izkazalo se je, da tudi pri izrisu končnih 2D vizualizacij na upodobitev barve vplivajo številni parametri in nastavitve, ki vplivajo na računske operacije in algoritme izrisa. Testne postavitve smo v programskem orodju Blender upodobili s tremi upodobljevalniki: Blender Render in Cycles, ki sta že vgrajena ter z vtičnikom YafaRay. Rezultati so pokazali, da vsi upodobljevalniki na barve ne vplivajo enako, da model barvnega zaznavanja CIECAM02 lahko uporabimo v 3D prostoru in da z njegovo uporabo dobimo boljše rezultate ujemanja barv pri spremembi svetlosti ozadja. Model barvnega zaznavanja CIECAM02 uporabimo tako na barvah v 3D prostoru kot na že izrisanih 2D vizualizacijah.Despite several technological advancements in the last few decades, we are still encountering issues regarding the reproduction of colors on different media and the achievement of color constancy. A possible option of ensuring constant color appearance are color appearance models, namely, the current color appearance model CIECAM02, which, despite having a great potential, is still not fully applied to practical workflows, especially in 3D computer generated graphics we come across on a daily basis. The purpose of this dissertation was to examine advanced color metrics and the CIECAM02 color appearance model to the point where it could have been implemented to 3D computer generated graphics. It was assumed that the CIECAM02 color appearance model can be used in 3D space, but it turned out that different setup parameters and settings influence the rendering calculations and algorithms which can, in turn, affect the rendering of color, too. Test setups were rendered with Blender software and three different rendering engines, namely, Blender Render, Cycles and the plug-in rendering software YafaRay. It was determined that rendering engines do not render color equally, that the CIECAM02 color appearance model can be applied to 3D computer generated graphics, and that by using the CIECAM02 color appearance model, we can significantly improve color matching when changing the lightness of the background. The CIECAM02 color appearance model can be successfully implemented on colors in 3D setups, or can be applied to already rendered 2D visualizations

CIECAM02 and Perception of Colour in 3D Computer Generated Graphics

Kljub tehnološkemu napredku zadnjih stoletij in desetletij se še vedno soočamo s problematiko prikaza in upodobitve barve v različnih medijih in ohranjanja zaznave barve. Ena od možnosti, za katero se lahko odločimo pri zagotavljanju stalne barvne zaznave, so modeli barvnega zaznavanja. Trenutno je aktualen CIECAM02, ki se še vedno ne uporablja v 3D računalniški grafi ki, s katero se vsak dan srečujemo. Namen raziskave je bil pregled barvnih prostorov v 3D računalniški grafiki, pregled reprodukcije barv in materialov, algoritmov za senčenje ter izbranih sodobnih tehnologij upodabljanja za doseganje korektne končne vizualizacije. V nadaljevanju smo želeli proučiti model barvnega zaznavanja CIECAM02 do te mere, da bi ga lahko uporabili v povezavi s 3D računalniško grafiko. V ta namen smo v programu Blender postavili testno sceno in jo upodobili s tremi upodobljevalniki: Blender Render in Cycles, ki sta že vgrajena, in z dodatkom Yafaray. Izkazalo se je, da CIECAM02 lahko uporabimo tudi v 3D prostoru in da z njegovo uporabo dobimo boljše rezultate ujemanja barv pri spremembi ozadja. Poleg tega smo ugotovili, da barv ne upodabljajo vsi upodobljevalniki enako. Omenjena raziskava je aktualna za vse, ki želijo svoje dvo- ali tridimezionalne izdelke predstaviti s pomočjo 3D računalniške grafike, torej tudi za področje vizualizacij oblačil in tekstilnih izdelkov, ki se uporabljajo pri modnem oblikovanju in oblikovanju interjerjev, avtomobilski, navtični in letalski industriji ter tudi širše, kjer so dovršene 3D vizualizacije tekstilij in oblačil nepogrešljivi element vizualnih in grafičnih komunikacij