Particle-based volume rendering

In this paper, we introduce a novel point-based volume rendering technique based on tiny particles. In the proposed technique, a set of tiny opaque particles is generated from a given 3D scalar field based on a user-specified transfer function and the rejection method. The final image is then generated by projecting these particles onto the image plane. The particle projection does not need to be in order since the particle transparency values are not taken into account. During the projection stage, only a simple depth-order comparison is required to eliminate the occluded particles. This is the main characteristic of the proposed technique and should greatly facilitate the distributed processing. Semi-transparency is one of the main characteristics of volume rendering and, in the proposed technique the quantity of projected particles greatly influences the degree of semi-transparency. Sub-pixel processing was used in order to obtain the semi-transparent effect by controlling the projection of multiple particles onto each of the pixel areas. When using sub-pixel processing, the final pixel value is obtained by averaging the contribution from each of the projected particles. In order to verify its usefulness, we applied the proposed technique to volume rendering of multiple volume data as well as irregular volume data.