In this paper, we proposed an evaluation model to quantify the viewing condition that enhances the material appearance of object without dependence on shape of object. The proposed model is based on viewpoint entropy which is used to find appropriate eye position. In order to establish this model, we first clarify the surface that have important information related to material appearance by measuring the gaze point with eye tracking equipment. Next, we added experimental results as a weight coefficient of material appearance into the conventional viewpoint entropy. We verified that our model is applicable to metal and ceramic objects by comparing the results between subjective evaluation and computational evaluation using the proposed model.