bagginsbill opened this issue on Jun 01, 2009 ยท 57 posts
bagginsbill posted Wed, 03 June 2009 at 10:44 AM
Using a plane for geometry instead of a sphere is no good because it doesn't reach all the way down to the horizon, even if its size is infinite. Using a sphere gets full coverage down to the horizon.
Mathematically, I'm actually implementing the clouds as a series of concentric spheres, not planes, because I'm applying the curvature of the earth to the simulation (yes, I really am). In my first post I was using an infinite plane, and that was producing bad results, because we were able to see clouds more than a thousand miles away. Depending on your altitude when you render with my latest setup, the farthest cloud you see is between 8 miles and 60 miles. Of course, at 60 miles, it's all haze, but they are there where they should be and at the right size because of perspective.
Moving the camera does affect the perspective a bit, but you are free to move the camera without too much problem up to about 400 feet from the center of the sphere. That's plenty of room for animation.
I already have a procedural star shader, also galaxies, nebulae, etc. The shaders can be combined quite easily. A better technique would be to set up two concentric environment spheres. The outer sphere would have clear sky, which could be day or night. The inner sphere would have the simulation. This would run a little slower, because there is a transmapping involved on the cloud layer, but it's only one layer as far as the renderer is concerned, even if it is simulating 100 layers. By layering the sky (or stars) and clouds in two spheres, you could put a moon prop between them. You could put a light source in the moon prop and the clouds will haze and light up near the moon.
You could also use multiple cloud spheres, for multiple layers of clouds (cirrus, stratus, etc). These layered spheres do not have to be at those actual distances. They just have to be nested by about 50 feet or more.
The possibilities are endless.
Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)