Abstract: We introduce a new type of model representation,the normal interpolation displaced surfaces (NIDS),which decomposes a geometric model into a simple domain mesh and a scalar-valued displacement field over it.The domain mesh represents the rough shape of the model,while the displacement field describes its details.We also provide a fast algorithm to convert geometric models from triangle mesh representation to NIDS.The domain mesh is obtained by constrained simplification.By taking advantage of the distribution of the normals over the domain mesh,a one-to-one map is maintained during conversion process, which serves also as the constraint condition.This representation is shown to be compact,accurate and easy to process.