So whats are octaves. With noise you have your basic output for each one. When you add an octave to that, you add another layer of the same noise, differently scaled on top of that. It is a different scale and/or rotation as your original texture depending on the Blending Options that you select.

     Now for changing octave levels. Open up the Noise Dialog Box by clicking on the Noise Dialog Marble (8). Now all you have to is click and hold on the Noise Octaves (39) control and drag it left or right. The default value is at 0 because that way you can tell what exactly your doing with the original noise. You can change the setting to a maximum of 8 but I find that I rarely if ever go past 3 octaves.

     One thing to keep in mind when you are working with octaves is that each time you add an octave of noise, it increases the render time. It has to calculate another layer of noise. Now if you pile on other render intensive processes this can greatly increase your render time. Just keep that in mind when your sliding that around. I find I almost always at least have one octave in almost every component in a texture.

     Adding layers of noise is great for adding detail, but the real control is how you blend them together. You can get very real appearing textures with lots of variation and detail. You can also get some very funky and cool results with some noises. If you wondered why the techno noise was so boring, just wait until you use multiple octave and blend them using the difference mode. To change between different Blending Modes simply click on the Noise Blending Mode (38) area in the Noise Dialog Box, and select from the list of Blending Modes. If you are familiar with layers in Photoshop, some of these will seem familiar to you. Most of the time you will have to adjust the frequency to really observe how the texture is affecting.

     Below is a list of all of the different blending modes and a short description of what they generally do. I believe there is a more technical description of them in the Bryce Manual, but I don't have mine with me now. My definitions are just to the best of my knowledge. Mainly it is just important to play around with each of them and see how different noises react with different blending modes. You can get some knock-you-socks-off textures with just a few clicks using blending modes. Remember to just experiment a lot.

 

Standard	Blends octaves by just averaging the values together.
*Noise without any octaves on left for comparison. Square - 1 Octave - Standard Blending Fractal - 1 Octave - Standard Blending
Irregular	Same as above just with more smaller details. Generally there is just a greater value range from black to white. It is very subtle, most of the times the difference is inconsequential.
More Irregular	Same as above just... more so (sort of).
* Square - 3 Octaves (High Frequency) *Standard Blending vs. More Irregular
Maximum	The values of all textures are compared and the largest value is used
Voronoi Distance1 - 1 Octave - Maximum Blending Techno - 1 Octave - Maximum Blending
MultiFractal	The octaves instead of being layered are just used to calculate an even more complicated fractal (I think, I don't really know how to explain it, but it makes sense to me). Basically it makes for a very nice texture that has a lot of variation. The more levels you add, the more real and complicated the texture looks and feels. Most of the time you will have to increase the Frequency of the texture to see it clearly.
RND Linear - 3 Octaves - MultiFractal Blending *Frequency Adjusted for effect Fractal - 1 Octave - MultiFractal Blending
With Rotation	The octaves are each consequetively rotated about 10 degrees and then blended together.
Square - 1 Octave - WithRotation Blending
Minimum	The values of all textures are compared and the smallest value is used
Stucco Noise - 1 Octave - Minimum Blending Fractal - 1 Octave - Minimum Blending
Multiply	The values of the octaves are multiplied together. Generally leading to a darker overall texture.
Value - 1 Octave - Multiply Blending Square - 1 Octave - Multiply Blending
Difference	Appears to subtract the two values together. This blending mode is very fun to play with. You can get some really cool results with it. It also works with 0 octaves.
Square - 0 Octave - Difference Blending Value - 0 Octave - Difference Blending
Minimum90	The octave is rotated 90 degrees and then the minimum value is taken.
* Linear Sine - 1 Octave - Minimum90 Blending *Set to 1d and adjusted rotation
Maximum90	The octave is rotated 90 degrees and then the maximum value is taken.
* Linear Sine - 1 Octave - Maximum90 Blending *Set to 1d and adjusted rotation
Auto-phased	Squishy. This just squishifies everything, no matter the octave setting.
Techno - 1 Octave - Displaced Max Blending
Displaced Max	Not sure, but the values tend to be more extreme. It seems like it just takes crossections of the textures and then just layers it on like magazine clippings glued on a piece of paper.
Square - 0 Octave - Auto-Phased Blending