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Building Convincing Terrain Materials in Bryce

We're going to use a three-texture material. That means that the alpha channel for Texture C will be used to combine Textures A & B. We'll start by building Texture A.

Open the material lab and select Texture A for the Diffuse color and the bump height. Also knock the Ambience down to 0 while you're at it. Now click the second top bottom to take Texture A into the Deep Texture Editor.

Initially, we're just concerned with how the Altitude and Slope filters affect the combination of the various components, so we're just going to use color before we start applying any noise.

Click the "3" in the top left to turn on all three components and set both blending modes to Average.

For all three components, set the color mode to "RGB" and "Linear Interpol3" and the Noise Type to "None". Now disable the second two components for now.

Now we're going to start playing around with the filters. Open the filter dialog and make sure Component 1 is selected. Select X(a*altitude+b) as the filter type. With this filter the "a" value controls the abruptness of the change while the "b" value controls the height at which it starts. Generally, if your "a" value is positive, then your "b" should be negative and vise versa. A positive "a" moves your color change and noise down from the top, while a negative value moves it up from the bottom.

For my purposes I selected an "a" value of approximately 3.6 and a "b" of about -0.83. I also use bright, highly contrasting colors to check the height and slope variations more easily. I came up with something that looks like the picture.

Next, we'll use the Slope filter for the second component. Enable the second component and select the X(a*slope+b) filter. Again, the "a" value controls the abruptness of the change while the "b" controls the level of slope at which the noise starts. Allegedly, with a positive "a" value, you can place noise on the vertical surfaces, but I'm still trying to get that to work like it says in the manual. So I always use a negative value to place noise on the horizontal surfaces.

For this material, I used a "a" value of about -3.15 and a "b"value of about 1.84. Again using highly contrasting colors, I end up with something like the picture.

Now it's time to make some noise! (Sorry....). Time to choose the noise type that will actually give us our texture. There are quite a few that are appropriate for natural rock, like RND Continuous, RND Linear, RND Saw, Turbulence and Fractal. Stuff like Stucco Noise and Stone Cliff are good alpha channels for combining textures, but I don't think they make good textures themselves.

The Vornoi noise types also make good rock textures.

Textures for this sort of work usually require high frequency settings, anywhere from 300% and up. Keep the octave settings low, from 0 to 2. Anything more and your texture gets too muted. All noise should be set for 3D, unless you're trying for layered rock appearance.

I also tend to avoid using Phase when building these textures. They are already complex enough with adding more rendering time.

Select different noise and frequency settings for both components 1 and 2. Also, enable component 3 and set a different noise and frequency for it. Component 3 does not get an altitude or slope, as this component fills in the gaps not covered by 1 or 2.

Also, be careful about changing the texture frequency in the material lab, especially with altitude filters. The texture frequency will affect the starting height of the noise. This is is another way of controlling your altitude changes, but be aware.

Exit the deep texture editor and set your bump height to something like 30. At this we point we get the image in the last picture. Not exactly "convincing" at this point, but it certainly has character.

Okay, for now we're going to stick Texture A in an unused channel, like Ambient Color and select Texture B for Diffuse and Bump. Repeat the steps above, but throw in a little variety. Change the order of components by doing the slope texture or the all-over texture first. Invert the values for the altitude filter so the noise comes from the opposite direction. Go wild and experiment.

Now's the time to build our alpha channel for Texture C. In the material lab, CTRL-Click (I believe that's Command-Click for Mac users) on the Texture C button for Diffuse Color and Bump Height, activating all three textures, using the C as an Alpha channel. Now take texture C into the Deep Texture Editor. The same noise types you used for your color and bump textures will work here, in addition to Stucco Noise and Stone Cliff.

Generally, noise in the alpha channel should be low octave, lower frequency and not heavily filtered. You're looking for high contrast. I usually use three components, using Blend Altitude and Blend Slope as my blending modes. This varies the manner in which the textures combine according to both height and slope.

Also make sure that alpha output is enabled for your components, of course. Bump and Color are irrelevant.

Okay, now it's time to take those wild colors we started with and replace them with the color we actually want to use. For my material, I'm aiming for a more desert-like rock formation, so I'm going to stick with the sandy yellows, tans, and pinks, with a dark brown or gold thrown in for "character."

Work through both textures, replacing your colors with more "natural" colors that suit the terrain you're trying to create. You might wind up with something like this.