Real-time rendering of volumetric clouds

Abstract: A common cloud-rendering implementation in computer-games is based on having a library of cloud-images. However, recent development has shown that it is possible to implement 3-dimensional volumetric clouds on current consumer hardware. This thesis presents and evaluates a volumetric cloud implementation that aims to further improve aspects of the already published solutions. The implementation relies on multiple different textures (both 2-dimensionaland 3-dimensional) along with values and functions to create the shapes of the clouds. To visualize the clouds, a ray-marching algorithm was used to incrementally step through the cloud-volume, sample the density, and calculate the lighting. To optimize the implementation, different experiments were performed to find the best parameter-values that resulted in good performance figures (render-time) while still achieving visually pleasing clouds. Without the clouds visual fidelity being compromised to much, the experiment results show that the number of steps taken towards the sun (for each step through the cloud-volume) can be lowered to a single digit number, and that the ray-marching step-length can be altered with relation to the ray-marching start distance, the global cloud coverage and the global cloud density. The resulting volumetric cloud implementation can seamlessly transition from low coverage to overcast, create different cloud types, handle different times of the day, and have clouds move across the sky.