At last, I found the motivation to try to improve my volumetric clouds rendering. On Mo's suggestion, I implemented an interpolated illumination cache. This patchwork show the result of the early tests. Left column are rendered with the original KH_Atmos plugin, the right column with the new one. All picture sizes are 800x600 pixels, AA 1, GD 2. Top row is rendered without cloud layer. Middle row has one cloud layer. Bottom row has the camera oriented far away from the horizon line. For base atmosphere, the sample stride is far larger than the cache grid size. This is why without clouds, the cache has almost no effect. Moreover, most of the top row rendering time is spent in the terrain. Middle row shows a moderate improvement (only 5 times faster). This is due to the horizon line. The main limitation of the illumination cache is that it becomes innefficient as soon as the sampling stride is bigger than the grid size, which is the case at some distance from the camera. Near the horizon line, this happen inside the cloud layer. Bottow row shows a huge improvement when the camera avoids the horizon line. The cache stays efficient along the whole cloud layer extent. In this experiment, the grid size is set to 1000.0 meters. Clouds self shadowing is damaged by big grid sizes. Using smaller grid size will give better selfshadowing at the expense of speedup. I plan to release the new plugin in one or two weeks, as soon as a few bugs will be fixed. Bernard