## 1 Introduction
Quadtree/Octree-based methods recursively refine quadrilateral/hexahedral elements to reach a desired level of refinement, resulting in conforming elements with arbitrary aspect ratios along material interfaces and domain boundaries. Mesh smoothing or optimization-based approaches are then employed to improve the element aspect ratios by iteratively relocating mesh nodes. While these methods can generate high-quality meshes for complex geometries/microstructures, they encounter two main challenges: (i) the high computational cost of iterative techniques such as mesh smoothing that are used to improve the element aspect ratios [22]; and (ii) occasional difficulty in convergence for intricate geometries, which might necessitate user intervention during the meshing process to change meshing parameters or manipulate the domain geometry. There have been several attempts at adapting or customizing meshing algorithms to generate conforming meshes for polycrystals. Neper [23; 24] is an open-source polycrystal reconstruction and meshing package that uses Voronoi/Laguerre mesh synthesized microstructures. Other researchers have also adopted Voronoi/Laguerre tessellation-based approaches for meshing polycrystals, as seen in [25; 26]. Although these iterative techniques can generate conforming meshes for simplified polycrystalline microstructures (e.g., with planar grain boundaries), their implementation for modeling more complex and realistic polycrystals can be challenging. DREAM.3D [15] can create more sophisticated synthetic polycrystalline microstructures with realistic grain shapes, size distribution, and crystallographic orientations compared to Neper. However, due to the challenges associated with meshing such complex polycrystals, DREAM.3D is only equipped with the ability to generate voxelated meshes. Although suitable for CPFE-based analyses, the use of such meshes can result in unrealistic stress concentrations and lower accuracy due to jagged representation of the grain boundaries. [PERSON] et al. [27] compared CPFE simulations on voxelated and conforming meshes and found that while macroscopic behavior, texture evolution, and stress/slip statistics may be similar, the conforming grain boundary representation provides a more accurate misorientation distribution and smoother stress field. For modeling intergranular damage, such as fatigue crack growth, generating a conforming mesh is crucial for simulating the problem. An open-source package worth mentioning for creating grain-conforming meshes is the XtalMesh Toolkit [28], which is capable of generating high-fidelity FE models for realistic 3D polycrystalline microstructures reconstructed using DREAM.3D. This study presents a comprehensive computational framework for transforming pixelated polycrystalline microstructure images into high-fidelity 2D conforming meshes. Before generating the mesh, a robust preprocessing engine is required to transform the raw pixelated image (here, synthesized using DREAM.3D) into an appropriate geometrical model of the polycrystal with smooth representation of the grain boundaries. This approach utilizes advanced image processing and computational geometry algorithms to identify individual grains, boundaries, and vertices, and characterize grain morphologies using Non-Uniform Rational B-Splines (NURBS). A modified version of the Conforming to Interface Structured Adaptive Refinement (CISAMR) algorithm [29; 30; 31], coined PolyCISAMR, is developed to generate conforming meshes for the resulting NURBS-based model. The CISAMR is a non-iterative mesh generation algorithm that transforms a structured mesh overlaid with the domain geometry into a conforming mesh. The proposed PolyCISAMR algorithm combines the non-iterative meshing capability of CISAMR with the added advantage of independent meshing of each grain, making it a segregated meshing algorithm highly suitable for parallel implementation.