Many factors, such as the number of vertices and the resolution of texture, can affect the display quality of 3D objects. When the resources of a graphics system are not sufficient to render the ideal image, degradation is inevitable. It is therefore important to study how individual factors will affect the overall quality, and how the degradation can be controlled given limited resources. In this paper, the essential factors determining the display quality are reviewed. We provide more details on our earlier presentation [Quantitative metric for 3D scene evaluation] on integrating two important ones, resolution of texture and resolution of mesh, to model a perceptual metric. We then present a preliminary study of the reliability of the perceptual experiments. Experiments demonstrate that the reliability of our user evaluations to be quite high. Finally, we also propose an approach for reducing user fatigue while performing perceptual quality