sRock is a simulation of particles suspended in a medium. “grain_size” represents the particle size. “diffusion” controls the amount of mixing between the particles and the medium. A diffusion of 0 will result in a sharp boundary between the particles and the medium. A diffusion of 1.0 will result in a complete blending. The variable “mix_ratio” controls the proportion of particles to medium. If it is 1.0, the color is entirely color1; if it is 0, the color is entirely color2. If sRock is applied as a bump map, then “mix_ratio” of 0.5 will result in even pits and bumps. If it is greater than 0.5, the surface will have discrete bumps. If it is less than 0.5, the surface will have discrete pits (depending on the parameterization of the surface).
If the surface is far enough from the eye that the grains become smaller than pixel resolution, the blur effect will cause the texture to become a single color. This is fine for color mapping, and helps to avoid aliasing problems. However, if sRock is applied as a bump map, the surface will appear to become smooth at large distances. A possible solution is to use an eccentric Blinn shader, which mimics the microfacets of the bump map. If you want a video snow effect, set the blur to 0.001 and the grain_size to 0.0001.
“sRock” is a solid texture.
| Argument Name | Absolute Range | Useful Range | Default | Description |
| colour1 (triple) | 0, infinity | 0, 255 | 255,255,255 | First color |
| colour2 (triple) | 0, infinity | 0, 255 | 60,0,0 | Second color |
| contrast | 0-1 | 0-1 | 1.0 | Controls contrast between two colors |
| grain_size | 0, infinity | 0-0.1 | 0.01 | Particle size |
| diffusion | 0, infinity | 0-1 | 1.0 | Controls amount of mixing between particles and the medium |
| mix_ratio | 0-1 | 0-1 | 1.0 | Controls the proportion of particles to medium |
| transformation_name | no default. |
| Argument Name | Absolute Range | Useful Range | Default | Description |
| amplitude | -infinity, infinity | 0, 10 | 1.5 | Amplitude of noise function |
| contrast | -1, 1 | -1, 1 | 0.5 | Contrast at boundary between vein and filler |
| diffusion | 0, infinity | 0, 10 | 0.5 | Degree of vein diffusion into filler material |
| vein_width | 0, 1 | 0, 1 | 0.1 | Thickness of vein material |
| filler_color (triple) | 0, infinity | 0, 255 | 255,255,255 | Color of filler material |
| vein_color (triple) | 0, infinity | 0, 255 | 76, 0, 0 | Color of filler material |
| 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. |
