In this paper

we present a multi-surfaces rendering method based on volume rendering for 3D data sets.First

we extract the boundaries between two different materials by weighting with gray-level gradient

and only voxels on these boundaries participate in the generation of each image

so it drastically reduces the rendering time.Second.We think the voxels on boundaries as the mixture of different materials

so in every voxel there is a surface.We use the oriented cube-interpolation technique to get the intersection point of viewing orientation and the surface in the voxel

then compute the surface normal of the intersection point.We use the normal to shade the voxel in order to improve the image quality.and make some experiments with medical CT images.