Abstract: Augmented reality systems can lead to major improvement of patient care by using the preoperative CT-Scan or MRI medical data intraoperatively during the intervention. In this study we propose to model human organs and laprosocpic instruments using constructive solid geometry (CSG) objects and we give some algorithms to watermark CSG modelled objects by finding an empty box in the bounding box of the object, then considering another CSG modelled object. We create a new CSG object with left leaf the original object and right leaf the other one, linked by minus operator. A great deal is to multi-resolution analysis and trees.