Summary: Multi-resolution techniques are commonly used to render volumetric datasets exceeding the memory size of the graphics board, or even the main memory. For these techniques the appropriate level of detail for each volume area is chosen according to various criteria including the graphics memory size. While the multi-resolution scheme deals with the memory limitation, distracting rendering artifacts become noticeable between adjacent bricks of different levels of detail. A number of approaches have been presented to reduce these artifacts at brick boundaries, including replicating or interpolating data between adjacent bricks, and inter-block interpolation. However, a visible difference in rendering quality around the boundary remained, which draws the attention of the users to these regions. Our ray casting approach completely removes these artifacts by GPU-based blending of contiguous levels of detail, which considers all the neighbors of a brick and their level of detail.