Quote from: WASasquatch on June 04, 2018, 09:18:25 PM
Could you define what your depth modulation is?
OK. So, first I think I should try to explain what happens when there is
no depth modulator. Every point in space has some cloud density that is calculated at that XYZ position according a bunch of functions. Let's say the cloud layer has altitude 500 and depth 1000 (and this is a Cloud Layer V2/V3). This defines a volume that starts at an altitude of 0 and extends to 1000 metres altitude. Anywhere in that volume the density could be >0. A 3D fractal plugged into the Density Shader input is used to calculate a density value that varies in space. If you have "taper top and base" turned OFF and "coverage adjust" at 0, then the Density Shader says
exactly where there is cloud and where there isn't. Any place where the Density Shader is below 0, there will be no cloud. Anywhere the Density Shader is >0, the density of the cloud at that point will be >0, proportional the value coming from the Density Shader. The actual density is further affected by "edge sharpness" and "cloud density" (more precisely, it is multiplied by "edge sharpness", then clamped so it never exceeds 1, and then multiplied by "cloud density"). "Coverage adjust" is an offset that is added to every value coming from the Density Shader before any further processing occurs, so has the same effect as changing the coverage adjust in the fractal itself. It changes where the edges of the clouds are simply by adding a constant to this number before it is clamped at 0, effectively changing the threshold at which cloud appears.
If you a build a cloud like this, you'll get clouds that are cut off at the top and bottom of the volume (at 0 metres and 1000 metres). To avoid that, we have the feature "taper top and base" which is turned on by default. This enables a built-in profile function that changes the threshold where cloud appears. It works a bit like "coverage adjust", but it's not just an offset, it also multiplies down the densities at the top and bottom. With this enabled, you can get clouds with round tops and bottoms simply by using a 3D fractal as the Density Shader, and it prevents clouds from ever reaching the exact top and bottom of the volume in which the cloud layer is calculated.
Most of the time when you're getting hard edges on your clouds, it's because of what's happening in those calculations I just described. Depth modulation isn't necessarily the problem.
Now for depth modulation. Instead of using a volume that is 1000 metres tall everywhere in space, it allows you to change this height. Assuming "centre" is set to 0 (the default), then it changes where that top is. A depth modulator of 0.5 will bring the top down to 500 metres above the base. A depth modulator is 0.1 will bring it down to 100 metres. The built-in profile is also squashed down to fit within this range.
If you have a very slowly-changing depth modulator, this should give you predictable results. If you have something that changes as quickly as the kinds of fractals we usually plug into Density Shader then you can get some nice cumulus clouds, maybe without even needing a Density Shader. This happens because every point in space can be calculated according to a new definition of where the top and the bottom of the cloud volume can be. But the way it works is very specific. Its purpose is to change the range of altitudes that are used to calculate the built-in profile and therefore where the maximum
potential extend of the cloud can be, which can be further modified by the Density Shader.
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From what you explain, 0 being black, and 1 being maximum (of I guess the cloud maximum depth), 0 is no cloud (0 height) 1 being top to bottom of depth...
Correct.
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Why would that definition include CUTTING the clouds to solid borders when dealing with shapes like a SSS?
I'm not sure I understand.
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Why can't it be REAL depth like clouds (a effort I'd assume you'd be striving for) and just modulate the depth if the clouds in whole? Or real depth like other programs that take what you have, and modulate it
I believe it does.
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, as apposed to creating something new? What is explained that it does, isn't the same as what it produces.
I don't know why you think this. You have some idea about how this works that I haven't understood yet, but if I can understand that then perhaps I can give better, more specific advice.
Matt