3DS MAX + OSL, Smoketunnel preview

Source GL: Nimitz cc3.0 OSL Code: The main volume noise is generated from a deformed periodic grid, which can produce a large range of noise-like patterns at very cheap evalutation cost. Allowing for multiple fetches of volume gradient computation for improved lighting. To further accelerate marching, since the volume is smooth, more than half the the density information isn’t used to rendering or shading but only as an underlying volume distance to determine dynamic step size, by carefully selecting an equation (polynomial for speed) to step as a function of overall density (not necessarialy rendered) the visual results can be the same as a naive implementation with ~40% increase in rendering performance. Since the dynamic marching step size is even less uniform due to steps not being rendered at all the fog is evaluated as the difference of the fog integral at each rendered step.