Multimedia content is becoming more widely used in applications resulting from the easy accessibility of high-speed networks in the public domain. An important component in multimedia content is 3D geometry, which in the past had low resolution due to acquisition, computational and network limitation, and was not able to approximate 3D surfaces realistically. Although processing speed and network capacity have been greatly increased in the last decade, the increase in demands for multimedia content surpass the increase in resources. Consequently, techniques for data simplification especially for 3D mesh data is inevitable in order to achieve shorter latency and satisfactory interactivity in applications. This paper presents a perceptual analysis to evaluate the visual quality associated with a change in level-of-detail. Our analysis is consistent to how the human visual system evaluates 3D objects in the real world and is based on the Just-Noticeable-Difference methodology. Experimental results show that our approach presents an accurate estimation of visual quality and thus provides a systematic method to evaluate the performance of different simplification algorithms.