Mojotech (not only) for Bryce Users: Tutorial

It's a
Material World

Materials in MojoWorld work the same way as in Bryce, or in any other 3D Application. They are the sum of all surface properties, including Textures. A lot of Brycers aren't very clear about the difference, and they often refer to Materials as Textures. In MojoWorld the difference is important. In Bryce, Materials are transparency, metallicity, refraction and so forth, added to Textures. You can make Textures without even being aware of a thing called a Material. In Mojoworld, you explicitly need to make a Material before you can apply Textures, except for the Textures which create your Terrain.
Another Difference, which more or less follows from this: In Bryce, Textures are applied according to slope, altitude, etc. In MojoWorld, you specify Materials by slope, etc, and then you "fill" them with Textures (which you can still apply by many different blend criteria).

Open the Terrain Materials Editor You know how to do it, because you read the pages I asked you to read...
You should see something like this:

It's the starting point for our "Material Tree" It works exactly like the Texture Tree. The Leaves have Kickstands, you can add Leaves, you can open and change controls. I'm not going into great detail like "click here to do this" - if you have forgotten how things work, have another look at the page about the Terrain Texture. When you are ready for it, add three more leaves, and name them, from top to bottom: Veg Material, Sand Material, Rocks Material 1 and Rocks Material 2. For each Leaf, you'll have a choice of a Water or a Displacement Material - always choose Displacement. Also, change the name of the Tree from "New Material" (or whatever it may be called in your version) to "Terrain Material Node". That's all for now - never mind what happens in the Real Time Render.
As you go along, watch the little arrow which connects all the Leaves together to the name of the Tree. As soon as you create the fourth Leaf, a second, unconnected arrow pops up. Also, notice the "b" Icons which are connected to 2 Leaves and other"b" icons. Clicking on the "b" reveals a Kickstand with controls to construct a blend between the two items connected to it, by Slope, Altitude, Value, and much more - very much like the blend between any two of the three Texture Components in Bryce, in the DTE. Clicking on the unconnected little Arrow changes the layout of the Tree and the way you can blend the Leaves. Click on it now, and you should see something like this:

The picture almost explains itself: We are looking at a Material Tree with four Material Leaves. They are arranged in two pairs. The two Leaves in each pair can be blended, and in addition to this, the two pairs can be blended with each other.
By default, each blend is set to "Maximum", which means (roughly speaking) that the lighter one of any of the two blended components at any one point on the Terrain is the one we'll see im the picture - exactly the same as the same option in Bryce or "lighten" Photoshop. It's one of those convenient conventions in Computer Graphics. Right now they all are the same shade of green, so all of our Terrain should be green.
Let us assign different colours to the different materials. Click on the "M" associated with the Veg Material. You should see something like this:

In version 1.1 "Transparency" was added to the Control Stack. It'll be missing in all my older screen captures.

Click on the "Diffuse" colour dot to call the Colour Picker and pick a nice colour for the vegetation. Don't worry about Specular and Glow. Specular is dark grey by default, which means very little specularity, and Glow is black, which means no glow. Repeat this step for all four Leaves. Make the colour for the two Rocks materials the same. You can use numeric entry in the Colour Picker.

Now, let us look at the Blends. Click on the "b" between the Veg and the Sand Materials. A little Kickstand appears, with just one DDLB. Select "Altitude", and look: there's the familiar Curve Editor Icon again, attached to the Kickstand. Click on it to open the Curve Editor. It looks like this, but with the usual bottom left to top right diagonal and with minimum/maximum input/output values set to 0 and 1 respectively. The settings shown here are for the Altitude Blend between the Grass and Sand of our Planet:

So, what does it all mean? OK, our sea level is at 700 meters above the Planet's surface. Let us say we want a transition between sand and vegetation to happen from sea level to 50 meters above. That's the range we are interested in, so we set our min/max Input to 700/750 to work in that range. Why did I invert the Diagonal? It's quite simple: Whatever is listed first hits the Input first, and gets applied at the lowest altitude. In our Material Tree, that's the Vegetation, and the Sand would fade in as the Altitude increases. That's the wrong way around, so we turn the diagonal upside down. Another simple example of re-mapping with the Curve Editor (don't worry about the reasoning behind it - when you learn the Pro Ui, you'll see where the Curve Editor fits into Mojowrlds dataflow, and you'll use it for things not even the programmers thought of).
If we want the transition to happen on higher or lower ground, we can entering pairs of higher or lower values to shift the Input range up or down. If we want to sharpen or soften the transition, we can decrease or increase the difference between minimum and maximum, respectively.
At the moment, this looks quite awful, but it'll do for now, as a working draft. Later in this tutorial, we'll learn how to create a more natural irregular transition line.

We want rocks to appear where the Terrain is too steep for sand and vegetation to cling to it. Click on the "b" icon for the blend between the two pairs of Leaves. we want the rocks to poke through both, sand and vegetation - that's why I chose to set things up this way. Choose "Slope" from the DDLB and look, there's our Curve Editor Icon again!

For Slope Calculations in MojoWorld, 1 means horizontal and 0 means vertical. The further to the left (towards "0" for the input) we shift the "drop" in the graph, the steeper the slope will need to be before the rocks show up. A less sheer drop in the graph will create a soft transition between rocks and the rest of the Terrain. Turning the graph upside down will result in Rocks on level ground and grass on our cliffs.

Why two Rock Leaves? I'll show you later, when I get to texturing the cliffs. Leave the blend between the two set at the default "Maximum" and it'll all make sense when we get there.

next on the Syllabus: how to deform those dead-straight cliff tops....
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