Feature Scale, Lead-in Scale * Smallest Scale

Started by Erwin0265, July 17, 2013, 07:57:16 am

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Erwin0265

July 17, 2013, 07:57:16 am Last Edit: July 18, 2013, 07:09:34 am by Erwin0265
Hey,
I'm playing around with the settings within the Power Fractal v3.
I just started with the default T2 scene and added a terrain > Power Fractal v3.
Test render > save.
Dropped Feature Scale from the default 5000 to 2000; test render > save. Now I'm buried within the terrain [dropping Feature scale = bigger terrain?....].
Increased Feature scale from 2000 to 10000; test render > save. OK - terrain is now lower..........
Dropped Lead-in scale from the default 25000 to 15000; test render > save. Terrain is.. er... different.
Dropped Lead-in scale from 15000 to 2000; test render > save. No change.
Increased Lead-in scale from 2000 to 10000; test render > save. No change.
Increased Lead-in scale from 10000 to 13000; test render > save. No change.
Increased Lead-in scale from 13000 to 20000; test render > save. No change.
Increased Lead-in scale from 20000 to 25000; test render > save. Thank God; it's back to the default settings and it changed back to the default appearance!

I thought I was going nuts!
However, now I am kinda confused. Why is there a change to the terrain only between 20000 and 25000? Shouldn't there be some sort of change when further lowering the Lead-in scale?

As you may gather, I am trying to use a systemmatic approach to working out how TG2 works; but if this is how things are going to go, I'm not sure whether I am using the right approach [aka. the Scientific Method]...............

I also tried increasing the Lead-in scale from 25000 to 35000 and there was a significant change [flatter with less features]..

I have always had a hard time understanding the relationship between Feature Scale, Lead-in scale and Smallest scale [although I think I understand the smallest scale parameter].
This issue is the same in Vue as it is in TG2; my understanding of these parameters just hasn't gelled..............
Help......

As I am still continuing with my exploration of the Power Fractal v3 in the terrain tab; I figured that I may as well keep adding questions [and hopefully getting answers in the not too distant future.. ;)].
I am now exploring the Colour Tab.
Does changing the colours have any effect at all when the fractal is within the terrain tab?
I have changed colours [thinking that perhaps the colours also had an effect on the displacement of the terrain] from black and white to blue and green; clamped either high and/or low colours; enabled/disabled high/low colours - all to an absolutely startling zero effect.
So I am assuming that the colour tab does nothing when within the terrain tab*?
*Instead of "Terrain Tab"; "Terrain Function" may be a better description? Of course, I am also still learning all of the TG2 terminology............
OK, who farted?

Tangled-Universe

Recently a Vue adept showed me Vue through Skype screen sharing option.
I remember starting with TG2 and am also remembering many others starting with it and thinking "what the heck does all of this mean"?
So for starters, you're not alone in this ;)
Furthermore, now that I understand most of TG's working and settings I also understand why those parameters and functions have their specific name.
That's something I'm missing quite much in Vue's UI.
It's both unclear what it is and on top of that the naming convention (if there's any) doesn't really suggest what it does for you.
On the other side some parameters have "slower" on one side and "faster" on the other side so that the user at least knows what to expect when moving that completely obscured and unknown slider setting ;)
I guess it's eventually about how much you really want to know or care about.

About the scale things:

Feature scale = the most common size of the noise's features
Lead in scale = "patch sizes" in which the noise is being generated
Smallest scale = smallest scale size possible for the noise function (from TG3 on that will be 0.01)

The number of octaves is a function of "lead in scale" vs "smallest scale".
As soon as the "lead in scale" becomes similar or smaller than the "feature scale" then the number of octaves becomes a function of "feature scale" vs "smallest scale".

The changes you have noticed are probably due to reaching the cutoff point where the octave calculations shift from being based on either the feature or lead-in scale.
Your approach wasn't very scientific, but it's probably what you observed.

What you also observed, the change in how low or high the terrain is, is not because of this directly.
The height of the terrain is based on the displacement factor.
So what you saw is that because of changing the scales the noise function itself changed and is multiplied with the displacement factor.
Since the generated noise can also be negative it means that your changed noise function contained a dip instead of where first a peak used to appear.

I would suggest you open the "base colours" node in the default, open its preview window (top right bluish screen button) and start playing with the scale factors.
Notice how changing feature scale does nothing to the octaves as long as you don't make it close or bigger to/than the lead-in scale.
Then if that becomes more clear then try the warp setting and set it to 2, for example.
Set feature scale to 1000 and then set lead in scale to 100 first and then to 10000 and notice what happens to the size of the warps.
What you should see is that the scale of the warping function is based on the lead-in scale.

Erwin0265

Thanks for responding.
The scientific method is one where one parameter is changed, keeping all others as they are; and observing the outcome.
This is based on zero knowledge of any and all other parameters' functions [at least, initially]; existing knowledge of other parameters' functions can lead to pre-conceived ideas that can result in "observations" being biased/manipulated to fit a pre-conceived idea.............

OK; that's the scientific method [same scientific method now being thrown out the window, in favour of asking others how to approach testing/observing]................. ;)

TU; I am not sure whether all of the first paragraph relates to Vue or not [I can't recall "faster"/"slower" parameters].
However, when it comes to any program, I would really like to know "everything", but realise that precious little artwork would ever be created if I were to use the "I must know everything before I can start creating anything."
If I can learn enough to know how to go about exploring TG2, then I will be a "happy chapy".
So;
The lead-in scale; as I understand your explanation; is the size of areas where the noise is being generated.........?

Something else that has me confused; colour setting within the terrain tab.
Colours set within the terrain tab do appear on the terrain but only until the base layer in the shaders tab is enabled. Is this correct?
What, then, is the purpose of colour settings within the terrain tab? I'm thinking that it's to allow one to see where certain features are located whilst building the terrain. These are then obscured by the base layer in the shader tab when colouring/texturing is done.
Am I anywhere near the truth here? Or am I making no sense at all?

Taking your advice [perhaps too literally]; the base colours preview window shows me nothing but shades of grey. Don't I first need to have some sort of terrain first before going on to the shader tab?
OK, who farted?

Tangled-Universe

Quote from: Erwin0265 on July 18, 2013, 07:08:35 am
Thanks for responding.
The scientific method is one where one parameter is changed, keeping all others as they are; and observing the outcome.
This is based on zero knowledge of any and all other parameters' functions [at least, initially]; existing knowledge of other parameters' functions can lead to pre-conceived ideas that can result in "observations" being biased/manipulated to fit a pre-conceived idea.............

OK; that's the scientific method [same scientific method now being thrown out the window, in favour of asking others how to approach testing/observing]................. ;)


Yes changing one parameter at a time is best.
Also going into one direction is far easier to be able to see what's going on and to understand it.
That was actually the thing I found difficult in your approach, as to me it seemed you were trying all kinds of things without a systematical approach. But hey, I'm me and you're you :) (that can't be English, lol)

Quote
The lead-in scale; as I understand your explanation; is the size of areas where the noise is being generated.........?


Yes that's a concept you can at least get started with.

If lead in scale is smaller than feature scale then you will notice there are no "islands" of noise, but noise everywhere.
The lead in scale normally creates these "islands".

Quote
Something else that has me confused; colour setting within the terrain tab.
Colours set within the terrain tab do appear on the terrain but only until the base layer in the shaders tab is enabled. Is this correct?
What, then, is the purpose of colour settings within the terrain tab? I'm thinking that it's to allow one to see where certain features are located whilst building the terrain. These are then obscured by the base layer in the shader tab when colouring/texturing is done.
Am I anywhere near the truth here? Or am I making no sense at all?


Yes this is a rather confusing concept for beginners I recognize.

Let me try to explain why:

The idea of building your terrain and shading is to this in stages.
The first stage is setting up your terrain, be it a heightfield or procedural (fractal terrain) for example.
Then, if necessary, you can displace the terrain further to add additional features or finer details.
This happens in the green terrain group in your node network.

You will see this group ends with a compute terrain.
This is where the surface of terrain (heightfield or procedural) and the displacements is being evaluated and updated for coordinates which can be used by surface shaders to shade the surface.

The compute terrain supplies the renderer with information about altitude and slope for each face of the surface.
So surface shaders can use this information which allows you to restrict your surface by altitude or slope or both.
This is what you will do in the shader tab; adding colours to your surface.

How the default is set up:

The default scene has a "base colours" node and if you open it and go to the colour tab you can see it has both high and low colour activated.
This means that this "base colours" powerfractal (it is a powerfractal shader) covers the surface 100%.
So any colour previously added in your terrain tab will be overridden, because this fractal has 100% coverage.
The two colours are black and grey and the contrast and roughness tab control how noisy the noise is and how much contrast there is between the noise features.
The offset shifts the coverage to either the high or low colour.

High colour = use this colour where fractal is present (white)
Low colour = use this colour where fractal is not present (black)
So if you disable the low colour then you'll only add colour where the fractal is present and vice versa.

If you use colours in the terrain tab then they won't show up as you may understand now.
Furthermore it is important to know that if you use a powerfractal to displace that the colour tab's settings do NOT affect the displacement.

The powerfractal is a versatile workhorse which allows you to displace or colour a terrain. You can do both actually, but that's rather advanced.
An advanced workflow would allow you to displace the terrain and use that same fractal to colour the terrain with the exact same pattern as the displacing fractal, but that's something which I'm not going into as it will become too confusing quickly.

Quote
Taking your advice [perhaps too literally]; the base colours preview window shows me nothing but shades of grey. Don't I first need to have some sort of terrain first before going on to the shader tab?


Now you should understand what these shades of grey are. It's the fractal pattern where grey represents the shape of that fractal pattern.
You don't need a terrain or any connection at all to see what the fractal pattern of a fractal looks like.
They generate the noise on its own without the need for input.
The gnereated noise can be affected of course when you connect a blendshader (mask) to the noise.

So just go into that preview window and start playing with those scale and other colour settings.

Later you can disable colour and start playing with the displacement settings to see what displacementfactor, offset, roughness and spike filters are doing.
(preview will automatically show solid grey for surface when no colour is enabled)

Have fun!

Erwin0265

July 19, 2013, 08:01:45 am #4 Last Edit: July 19, 2013, 08:08:54 am by Erwin0265
QuoteSo any colour previously added in your terrain tab will be overridden, because this fractal has 100% coverage.


So why have a colour setting at all in the terrain tab?

QuoteIf lead in scale is smaller than feature scale then you will notice there are no "islands" of noise, but noise everywhere.
The lead in scale normally creates these "islands".


These "islands", are they the coarser texture [grey/black], whereas noise everywhere is manifest as just grey with little change in shade?

QuoteThe offset shifts the coverage to either the high or low colour.


Huh????? ???

QuoteFurthermore it is important to know that if you use a powerfractal to displace that the colour tab's settings do NOT affect the displacement.


I'm starting to think that this is as much an exercise in understanding the terminology as it is the actual functions of these settings.....
I am thinking that you mean that if I use a powerfractal in making my terrain, the colour settings within that particular powerfractal will not affect the terrain shape; only the colour - which is fully covered by the base shader. Which again brings me back to, why have them [the colour settings] at all when using a powerfractal to displace [create terrain - I can assume these 2 terms are synonymous?]?

QuoteYou can do both actually, but that's rather advanced.


Err, can I please put in an order for extra basic please?

QuoteNow you should understand what these shades of grey are. It's the fractal pattern where grey represents the shape of that fractal pattern.


OK. What I tried first was going to the base shader, clicking on the little window icon, enlarged it [can't see anything in that little window], let it render fully, took a screencap, increased the Feature scale 10-fold, let it render, screencap, increased again 10-fold, etc - until both feature and lead-in scales were 1000.
Then I reset to default and went through the same process with the lead-in scale.
I now have eight grey squares [yeah, I'm being facetious, but only a bit - I can't really see any sort of trend].
I really don't know what I am meant to see.
I did change the colours to determine if I could see more, but it was pretty-much the same mess........
Things that I may see are;
1. As Feature scale increased, the grey became more "homogenous" - there was less "grain", less black bits......
2. As Lead-in scale increased, more course areas became visible [but they didn't appear around already coarse areas; I am interpreting these areas as areas of terrain, so the terrain locations would "bounce" around until lead-in scale was set. Now, I know that can't be right!].
I have attached my 8 grey squares below [as one image  :)]. Am I at least going about this the right way or have I completely misunderstood what you meant for me to do?

I forgot to mention; with the summary image, the labels indicate the one adjustment/setting that I was changing - all others were left at default - so the image at the start of each row should be the same.
As I have just written this; I realise I mislabelled the summary pic.
Update coming in a few minutes :-[.
OK. updated
OK, who farted?

Tangled-Universe

I tried to structure my response as best as possible, yet it didn't seem to work :D
I would suggest to read it again, line by line, piece by piece.

I guess I will make a video somewhere this weekend, because I've just spent 20 minutes on trying to write down what you are missing, but it's just too elaborate.

It requires too many lines to explain a concept which is supersimple once you get it, but I remember clearly how long it took for me to get it as well, so you should definitely not feel offended by it. Rather feel supported by the idea that you're definitely not alone in this :)

Erwin0265

If you have the time to make a video, it would be very much appreciated [not just by me, but by many others, I imagine].
I look forward to it; your three introductory videos are pretty much the best I have seen online.........
Cheers and thank you very much...........
OK, who farted?

Erwin0265

OK,
I have to admit that I am a little disappointed.
It's been just over 3 months and I am still waiting for the video you promised.
I realise that the offer came from the goodness of your own heart and that you weren't obliged to create anything.........
But you did offer to do it and I have purposely not made further posts on the subject as annoying you aint gonna make it come any faster.
However, I am now making another post in the hope that you may have forgotten [but then, your CGScenery site also appears to have had nothing done to it over the past three months; so, I'm kinda confused......].
Although the vast majority of the past three months have been spent in hospital [I'm sort off put together wrong; I think they lost the plans.........], when I have been able, I have gone back to Vue and Photoshop [Photoshop is fine but Vue pisses me off, but at least I can do something with it - I still have this block with Terragen].
Anyway, I hope you can respond to this and that all is OK with you.
The reason for posting further here [rather than PM], is to remind you of the topic and [if you weren't able to reply] so others could respond also..............
OK, who farted?

Dune

Usually Martin is very keen on answering any question, and quite involved in the whole Planetside business, but I guess he's either out of the country or very busy with something. He has a demanding job, as far as I know.
I suggest experimenting a lot and see what you can work out by yourself. I did it that way.

Erwin0265

Hi Dune,
Thanks for the reply.
I was hoping it was something like that [rather than something bad, as happens to me with all my health issues - I end up not responding to someone in a forum, or getting back to a friend, etc...basically because I'm back in hospital or similar. I wouldn't wish that on anyone....].........
I have tried the playing around route and I was getting myself more and more confused; which is why I posted in the forums - and Martin has been kind enough to try to help me with.
But, as luck would have it, no amount of explanation would get through my thick skull [I used to be a maths/science teacher that most of the kids liked and respected; because I could understand why they didn't understand. I think it made me a better teacher.].
I am very much a visual learner and have difficulty understanding only text [gimme a few pictures and I'm happy  ;)].
So when Martin offered to make a video; Eureka! I had already seen his other vids on his site and they are some of the best I have seen on the subject of Terragen.
I have stacks of scene files and clip files; along with lots of forum posts that I have turned into my own little tutorials, but I need to get past the basics before I can use any of them with purpose [it's easy enough to open a tgd, change position, render and say, "I made this." - but I still have no clue - nor am I honest if I do that......].
Anyway, I can wait; I'm going back and relearning perspective drawing [funny what you forget over the years when you all of a sudden want to create something only to discover, "Now how the hell did I do that before?"]......... so I'm keeping busy.
I just hope that Martin will find the time..........., err, sometime, in the future, as I think he may be right in that I am bogged down with what is [or will become - for me, hopefully] a simple concept............
Honestly, when I get past this and start really learning, I will be most happy to write tutorials - it helps me consolidate my knowledge and I know I am good at it [after 25 years of teaching 11 - 16-year olds, I should be good at it.  ;D].
Cheers - sorry for the rambling post.......
OK, who farted?

archonforest

Thx for starting this topic Erwin....lots of valuable info in there... ;)
Dell T5500 with Dual Hexa Xeon CPU 3Ghz, 32Gb ram
Amiga 1200 8Mb ram, 8Gb ssd

Erwin0265

It's a shame I'm too thick to understand what TG is trying his level-best to explain to me............... ???
Hopefully someone will take pity on me and create a picture book for me [and a dummy would be nice; or do you guys call it a pacifier?........].
OK, who farted?

archonforest

Well I do understand your problem. Reading a text only(significance) without having the mass of the subject(a picture of the subject or similar) not so easy. I would suggest to you to find some tutorials on the net(I did the same) and just do them. While u following the steps of the tutorial u can learn stuff. That gives some mass to the significance and i am sure u will succeed. :)
Dell T5500 with Dual Hexa Xeon CPU 3Ghz, 32Gb ram
Amiga 1200 8Mb ram, 8Gb ssd

dandelO

October 25, 2013, 08:35:32 pm #13 Last Edit: October 25, 2013, 08:42:38 pm by dandelO
Hi, Erwin.
There is an excellent thread here that I advise everyone to read, it really helped me grasp many, many things of the general workings and terminology of TG. Please also read it and *follow along with Terragen open as you do*.
Use the forum search function to find a topic titled 'PowerFractal Lessons' by Volker Harun. It is a very informative thread, with detailed explanations and plenty of images for every step of the way. Volker talks you through many of the areas you're having trouble with in a very concise and friendly, patient manner. I would say it is the single most important topic that I've read here, it made so many of these difficult to grasp settings and sometimes intimidating technical terminology that Terragen uses crystal-clear, and with that a much better understanding of much, much more than just the thread's title suggests. I often advise people struggling with TG to read that thread, please do, I guarantee you won't regret it. :)

Erwin0265

Thanks, dandelO; I downloaded that particular thread a while back and started to work through it but got lost along the way...
But that was over a year ago and my understanding of all things digital has improved over that time.
I will dig it up and go through it again and see how I go.
However, it will have to wait until Summer comes around as this is when I am often stuck inside due to the heat............
I really need time to work through these [apparently] foundation concepts; short sessions [like the evenings after dinner] allow for too much time inbetween; just enough for me to forget what I have just learnt [the result of all the medications I am taking...].
Anyway; enough waffle. Thanks for your suggestion - I will definitely give that thread another go............
OK, who farted?