The sCloud procedure is commonly used to create effects such as smoke and steam in addition to clouds. The transparency level of the cloud area itself can be interactively adjusted. The area surrounding the cloud is always transparent, regardless of the type of mapping used.
sCloud requires that the geometry being textured is a sphere. The spheres can be transformed in any way (for example, non-proportionally scaled), but the actual base component must be a sphere. Any other geometry will give unreliable and/or unpredictable results, although you are not prevented from doing so.
When using sCloud for non-color mapping, it becomes a solid fractal texture that has an added threshold depending on surface orientation.
As a surface curves into outline, the threshold is increased and added to the fractal, the result is clipped to 1.0. If this technique is used to transparency map ellipsoids (non-proportionally-scaled spherical patches), the results look like puffs or clouds. If the texture is applied to non-ellipsoidal shapes, the results will be of unreliable quality.
A series of nested ellipsoids; can be used to simulate fiery smoke. Each ellipsoid is given a transparency map defined by sCloud. This procedure creates a fractal with a slope-dependent offset added to it. This leads to an opaque center and a ragged transparent edge. Each ellipsoid looks like a puff of smoke. The fire effect is achieved by making the ellipsoids have different optical properties. The outer ellipsoid is made gray and dim. The inner ellipsoids are made successively brighter and more orange.
| Argument Name | Absolute Range | Useful Range | Default | Description |
| contrast | -1, 1 | -1, 1 | 1.0 | Relative contrast for color1 and color2 |
| colour1 (triple) | 0, infinity | 0, 255 | 60, 0, 0 | First color |
| colour2 (triple) | 0, infinity | 0, 255 | 255,255,255 | Second color |
| transparency_range | 0, infinity | 0, 1 | 0.5 | Transition range for texture value |
| center_threshold | -infinity, infinity | -1, 0 | 0.0 | Threshold value for face on surfaces. |
| edge_threshold | -infinity, infinity | 1.0, 2.0 | 1.0 | Threshold value for outlines |
| soft_edges | TRUE FALSE | FALSE | Makes the texture color blend to black as surface tilts away from eye. Good for flame effect when used with incandescence mapping on ellipsoids. The alpha channel always does this blending, regardless of this flag. | |
| amplitude | 0, infinity | 0-100 | 1.0 | Noise amplitude |
| xripples | 0, infinity | 0, 100 | 1.0 | Fundamental frequencies for noise function |
| yripples | 0, infinity | 0, 100 | 1.0 | " " |
| zripples | 0, infinity | 0, 100 | 1.0 | " " |
| level_min | 0, infinity | 0, 50 | 0.0 | Minimum allowed level of iteration |
| level_max | 0, infinity | 0, 50 | 20.0 | Maximum allowed level of iteration |
| ratio | 0, 1 | 0, 1 | 0.707 | Ratio for fractal noise |
| transformation_name | no default. |
“sCloud” is a solid texture.
