An efficient algorithm for generating a set of concentric spherical slicing surfaces for volume rendering of irregular volume datasets is presented. Our original algorithm, which approximates volume rendering by accumulating concentric spherical slicing surfaces from back to front, generates these surfaces by means of a conventional isosurface generation algorithm. However, this causes a performance bottleneck. To solve the problem, we propose a proliferous generation of slicing surfaces from seed cells, which are automatically determined according to the extremum points of the values of distances from a viewing point. A benchmark test shows that this approach can improve the performance significantly. In addition, we compare this algorithm with a ray-casting algorithm that we proposed previously, and discuss a criterion for selecting which one to use for maximizing the performance