What is VTI?

VTI most likely refers to Volume Texture Illumination. This is a rendering technique used in computer graphics to simulate the interaction of light with volumetric data. It's commonly used in medical imaging (e.g., visualizing MRI or CT scans), scientific visualization (e.g., displaying fluid dynamics simulations), and special effects in movies or games, allowing for realistic rendering of fog, smoke, clouds, or other participating media.