We have earlier proposed a voxel-based representation of an elastic object that can respond to a user's input in real-time for haptic rendering. We called it shape-retaining chain-linked model or S-chain model. The S-chain model is constructed from the 3D voxel data of an object, where each voxel is a chain element that is linked to its six nearest neighbors. Its deformed configuration is computed, upon the user's input, by propagating outward the unabsorbed input force from the interaction point as if a chain is pulled or pushed. The deformed configuration is then used to compute its disturbed internal energy that is reflected to the user. The basic idea of force rendering is that the reflected force is proportional to the number of chain elements that are displaced from its initial position. This simple nature of the model allows very fast deformation of a volumetric object so that it can be utilized in real-time applications. In this paper, we present a mechanical interpretation of the haptic model as to how the reflected forces are being computed by utilizing spring-and-cylinder units. Furthermore, we investigate the quality of the haptic feeling of the S-chain model by comparing with that of FEM against the human haptic perception. The result of our experiments demonstrates that S-chain model provides not only the realtime performance but also the quality of FEM with respect to our haptic sense.