Computational mechanics has been recognized as a powerful tool for cardiovascular disease research, vascular surgery planning and medical device design. The accurate and efficient construction of anatomic models is a critical element in the application of these computational methods. We developed an interactive modeling system for the computational biomechanics simulation using medical imaging data such as MRI or CT. The novel aspect of this modeling system is that the operator can modify the model which is rendered over the reference volumetric images. Therefore efficient modeling can be done with help of the heuristic knowledge of the operator.