Crack-Free GPU Tessellation for Real-Time Visual Bone Drilling in Virtual Arthroscopic Simulators

Background/Objectives: Real-time arthroscopic bone drilling in simulators requires high graphics and haptic update rates while deforming bone visually. We present a fully GPU-resident, shader-based pipeline for the Virtual Rotator Cuff Arthroscopic Skill Trainer (ViRCAST) that avoids mesh regeneration. Methods: Instead of changing geometry, the method updates a vector displacement map and a tessellation amount map. The pipeline uses six GPU passes: drawing-vector calculation, displacement-map generation, tessellation-map generation via Sobel edge detection, mipmapped tessellation sampling, vertex displacement, and fragment-level normal correction. A patterned-drawing scheme reduces stretched-triangle artifacts, and an edge-symmetric UV rule assigns identical tessellation factors to shared edges. Results: On a Dell desktop with an Intel Core Ultra 9, NVIDIA GeForce RTX 5090, 32 GB VRAM, 128 GB RAM, and Windows 11, 1000-frame GPU timing showed that 4K texture updates completed in 0.292 ms on average, and the full drilling update completed in 0.397 ms. This is far below the 16.7 ms budget for 60 Hz rendering. The pipeline sustained 120 fps in multi-object scenes and improved frame rate by up to 24% over uniform tessellation, with SSIM ≈ 0.99992 on depth output. Conclusions: The method provides surface deformation, complements volumetric drilling modules, and supports continuous feedback for surgical training.