Move the range overall towards the left, you're effectively making most of the image dark, move it all to the right, you're making most of the image light. You can think of moving the points of the ramp around like adjusting the brightness and contrast of an image put the start and end points close together, you're increasing contrast. Vector axis axis = chv ( 'axis' ) axis = normalize ( axis ) a = noise ( P + Time ) a = chramp ( 'noise_rerange', a ) axis *= trunc ( a * 4 ) * $PI / 2 orient = quaternion ( axis ) The numbers themselves are gobbledygook for the most part, the only time I recognise what an orient is doing is when its at no rotation the local x/y/z of each copy matches to the world xyz: Orient is a 4 value vector, so it's nice and compact to store. The reason is that its the most unambiguous way to define rotation. That means it takes priority over everything else. On the instance attributes page you'll see that orient is at the top of the list. This is probably gonna be way over 30 mins today, but I think it's useful to have all the orient related stuff on a single page. So some of this intro stuff you'll have to take on faith, I'll explain details later. When I came back to it via Houdini and instance attributes, I took some advice from Matt Ebb don't try and understand whats happening under the hood, just care about the end result, and what it can do for you. Or is it? When I first heard about quaternions many years before getting into Houdini, I tried to understand the maths and got myself hopelessly confused, gave up. There's another way to do this, which involves jumping to scary quaternion land, 4 dimensional values, unintuitive concepts. In the previous lesson we went learned how you can use and to define a stable rotation. 5.12 Bonus: transforms and attribute types.5.7 Transform operations and attribute types.5.1 Make this rotation thing do what we want.
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