Anisotropic reflectance model for predictive rendering of FDM prints
ID Boc, Ana Gaja (Author), ID Marolt, Matija (Mentor) More about this mentor... This link opens in a new window, ID Rittig, Tobias (Comentor), ID Podpečan, Vid (Comentor)

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Ray tracing is a fundamental rendering technique that simulates the interaction of light with 3D scenes to generate photorealistic images. Rendering speed is intricately linked to the intricacy of the scene and the properties of the materials. This challenge is particularly pronounced when rendering objects produced through Fused Deposition Modeling (FDM), given their high polygon count and the presence of subsurface scattering characteristics within the printing material. This thesis was dedicated to the development of a shader with dual objectives: first, to approximate object geometry through the utilization of a bump shader and second, to bypass circumvent the computationally intensive simulation of subsurface scattering. The latter goal was realized by constructing a Bidirectional Reflectance Distribution Function (BRDF) function based on material measurements. In addition to these shader developments, we conducted renderings of objects with explicit geometry, directly derived from the printer's instructions, incorporating subsurface scattering and plastic reflections. These renderings served as benchmarks against which to evaluate our shader results. We also compared our rendered images with photographs of the corresponding physical printed objects with matching light sources and camera positions. Using our shaders, we successfully achieved a significant improvement in rendering times. The material shader produced results that closely aligned with the benchmark renderings. However, with respect to our bump map shader, while it delivered accurate results for planar surfaces, some discrepancies emerged on spherical surfaces. It is worth noting that these results are considered to be as close to the original as is practically attainable within the shader framework. For a more precise match, it would be more feasible to engage in some sort of geometry preprocessing.

Keywords:light transport simulation, appearance fabrication, 3D printing, reflectance modeling
Work type:Master's thesis/paper
Typology:2.09 - Master's Thesis
Organization:FRI - Faculty of Computer and Information Science
PID:20.500.12556/RUL-152350 This link opens in a new window
COBISS.SI-ID:177579779 This link opens in a new window
Publication date in RUL:22.11.2023
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Secondary language

Title:Anizotropni model odbojnosti za napovedno upodabljanje FDM tiska
Sledenje žarkom je računalniška tehnika, ki simulira interakcijo svetlobe s tridimenzionalnimi scenami za ustvarjanje fotorealističnih izrisov. Hitrost izvajanja te tehnike je močno odvisna od kompleksnosti same scene ter od fizikalnih lastnosti uporabljenih materialov. Upodabljanje tridimenzionalnih natisnjenih objektov s tehniko tiskanja FDM (ang. Fused Deposition Modeling) prinaša izzive v obeh aspektih. Za filament uporabljen za tiskanje je značilno podpovršinsko sipanje svetlobe, medtem ko ima geometrija natisnjenih objektov visoko število poligonov zaradi vidnih plasti filamenta, ki se oblikujejo med postopkom tiskanja. Cilj te naloge je bil razviti senčilnik za preslikavo tekstur (ang. bump mapping), ki bi omogočil aproksimacijo geometrije in tako zmanjšal potrebno število poligonov, za upodobitev objekta. V izogib simulaciji podpovršinskega sipanja znotraj materiala pa smo na podlagi meritev odbojnosti izdelali tudi senčilnik za aproksimacijo izgleda materiala. Za primerjavo smo tudi generirali objekte z geometrijo, ki bi jo imeli, če bi bili fizično natisnjeni. Geometrijo teh objektov smo pridobili iz G-code datotek, ki vsebujejo navodila za tiskanje. To geometrijo smo nato uporabili skupaj s simulacijo podpovršinskega sipanja svetlobe in modeliranjem plastičnih odbojev, ki so značilni za uporabljeni material. Rezultate naših senčilnikov smo nato primerjali z upodobitvami dejanske geometrije in pa fotografijami natisnjenih objektov, ob tem pa smo se trudili vzdrževati enake pogoje osvetlitve in položaja kamere. Uporaba naših senčilnikov je prinesla opazno izboljšanje hitrosti upodabljanja. Rezultati senčilnika za material so se izkazali kot izjemno usklajeni z referenčnimi upodobitvami. Senčilnik za geometrijo se dobro obnese pri ravnih površinah, medtem ko so se na ukrivljenih površinah pojavile razlike v primerjavi z referenčnimi izrisi in fotografijami. Kljub temu smo mnenja, da bi bila za boljše ujemanje potrebni izračuni, ki so preobsežni, da bi se izvajali znotraj senčilnika in bi bilo bolj smoterno, da bi se za boljše rezultate implementiralo predprocesiranje geometrije.

Keywords:simulacija prenosa svetlobe, fabrikacija videza, 3D tisk, modeliranje odbojnosti

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