Design and Implementation of a Library of Functions for Hybrid Volume Rendering Using OpenGL

InViVo-Brachy is a navigation system for brachytherapy treatments, included in the InViVo (Interactive Visualiser for Volume data) environment. In this system a 3D reconstruction of the body of the patient (from a CT data set), as well as cancerous tumours inside the body and the interstitial needles for the radiotherapy treatment against those tumours are displayed. All these different types of data (volume elements and flat elements) have to be visualised together in the same scene. That Hybrid Volume Rendering (HVR) process is here carried out by mean of two independent processes: Volume rendering of the volume data (from CT data set), using the raycasting technique and geometric rendering of the flat elements (needles, drawing of the tumour, etc.), using OpenGL graphics API. In this HVR both rendering processes share common parameters that unify their scenarios, but the independence of the processes provides flexibility, decreases the computational cost of the joint process, and uses the best specific features from each rendering process.