Abstract: Techniques for accelerated opacity correction for over-sampled volume ray casting on commodity hardware are described. The techniques exploit processing capabilities of programmable GPUs and cluster computers. The GPU-based technique follows a fine-grained parallel approach that exposes to the GPU the inherent parallelism in the opacity correction process. The cluster computation techniques follow less finely-granular data parallel approaches that allow exploitation of computational resources with minimal inter-CPU communication. The performance improvements offered by the accelerated approaches over opacity correction on a single CPU are also exhibited for real volumetric datasets.