Mojotech (not only) for Bryce Users: Tutorial

Terrain Shaping
using the
Curve Editor

Let us see whether we can make MojoWorld do exactly what we want. I want cliffs as a feature of this Planet. The shape of the output of the Basis Function determines what the Landscape looks like, because the Fractal distributes it throughout the World. But there doesn't seem to be a function which resembles cliffs...

Meet the Curve Editor: Open the Kickstand for the Texture "Terrain 1" and click to select the Output Control. A widget shows up in the top left of the Editor Window. Change the name to "Terrain 1 Output" and click on the little Graph Icon. Something like in the picture below should open, with a diagonal instead of the curve I set up to create the cliffs. Some information about selected points on the Curve (shown below the Graphs) is missing in these Illustrations - it's a new feature since version 1.1.

This is all we need to duplicate the functionality of the many Texture Filters in the Bryce DTE. It's also easier to use, I reckon. This single Dialogue is so versatile, there'll be no end of side bars to this tutorial as we explore it deeper.
It can take any values as an input and change them according to rules we set up. Here, we use it to re-calculate the height for each point on the surface of our Planet to change the Terrain shape to resemble what we want. Staggering! If you still have a not all that old Atari or Commodore computer, try it on that...
There's actually a simplified version of this particular use of it in the Bryce Terrain Editor, sitting behind the "Filter" tab.

But this one lets us do more! Try this, very quickly, and I'll explain in a moment:

- click Cancel (you should be back in the Texture Editor now)
- click in the Kickstand to edit the Mountain Fractal
- set the Result Scale from 5000 to 1 (your Terrain should go flat and sink into the Ocean)
- go back to the Curves Editor (via Output Control)
- change the Maximum Output from 1 to 5000 (your Terrain should rise again)
- stop to think about it for a moment
- try to say what you just saw, what you did, in your own words.
- set the Maximum Output back to 1 and the Result Scale back to 5000
- open the Curves Editor again and read on

The Curves Editor scales the Output the same way as the Result Scale does. You just re-mapped a range of input values from 0 to 1 (the output of the Terrain height calculation) to a new output range from 0 to 5000 (the tops of the highest mountains). You did it by multiplying the height of all points on the surface of the Planet by a factor of 5000.
You can also "distort" this "linear response" like you might know if you've used this filter's ancestor in the Terrain Editor. If you haven't, you'll probably use it a lot after you're done with this tutorial.

Let us make the cliffs. First, let us bear in mind that the output range of the Terrain calculation for our Planet so far goes from 0 to 5000. As a side note: the actual output of our Basis Function, processed by the Fractal was originally from -1 to 1. That's the way the mathematics of MojoWorld work. To calculate the land height, we only looked at the positive values, and we multiplied the result by 5000.
Consider and do these steps:

- the horizontal of the Graph represents the range of input values into the filter
- the vertical represents the range of output values
- we multiplied the range of the output of the Terrain calculation by 5000
- we are using this range as the input into our "filter"
- change the Maximum Input from from 1 to 5000
- change the Maximum Output from from 1 to 5000
- set up a curve as close as possible to the one you see above (the manual explains how, and the controls are very intuitive)
- click OK

Cliffs!!! But the top edges look like drawn with a ruler. And they cover the Planet evenly, with only shallow hills on the tops and shallow slopes at their feet. Heh! Beaches!
Play with the Curves Editor for a while. Change the slope at the point where the curve exits the the top right corner of the graph, move the points around, and make notes of what's happening to the land shape. Also, change the "beyond Output" and "beyond Input" behaviours, using the DDLBs in the Curve Editor. Mountains can be taller than the specified 5000 meters, depending on how values outside the ranges we are workin uin are treated. You'll develop a feeliung for it as you experiment.
Don't forget to set the curve back to something close to the picture above and take a break. Fly around the Planet and see how the upper cliff edges are all the same hight, and the distribution across the Planet is still boringly even. We'll change this later, but first, we'll create some materials to make our preview a little better to look at.