Population altitude setting T2

[bigben]

A lot of this has to do with the combination of masks.  The problem with your first explanation is that you are visually defining where the border of the "node colour opacity" is. In frame 5, for example, you have a fuzzy zone that is equal to the difference in the max/min altitudes (2,000 & 1,000) you use in the demo, and with a resulting border halfway between two (1,500). At this point the surface has an opacity around 65%. This isn't a bad visual approximation for a single fuzzy zone.

When you then define 2 fuzzy zones, they will interact with each other. In frame 9 of your animated GIF for example, the upper and lower fuzzy zones will have an opacity of 65% at 1,700 and 1,300.  But these 2 masks overlap and their combined effect reduces the opacity of the surface so that the "border" appears to be half way, but it's opacity will be less that 65%. 

The application of the fuzzy zone to negative altitudes doesn't appear to be quite right. It seems to be behaving as if the fuzzy zone is being shifted downwards rather than starting at the altitude restriction.

In you're example where you use negative numbers for both fuzzy zones, you shouldn't see any surface because one of the masks will always have a value of zero. 

[Kadri]

Not much to say Ben. I wanted to see and test extreme settings too.

...
The application of the fuzzy zone to negative altitudes doesn't appear to be quite right.
It seems to be behaving as if the fuzzy zone is being shifted downwards rather than starting at the altitude restriction.
...

I am not sure about that too. But if i haven't missed anything the only difference was the negative number.
But considering what i knew before this thread i am quite happy with the results for now.
Especially as my brain got very fuzzy too at testing all those (and more) settings tonight

[bobbystahr]

It still seems to me that in my tests the colour is rising with the fuzzy zone change/increases; the height does not change at all....

[Dune]

Interesting tests, Kadri (never enough testing done!), but I think negative numbers don't really serve a purpose here. In other shaders they surely do have their uses!

[Kadri]

...but I think negative numbers don't really serve a purpose here. In other shaders they surely do have their uses!

Not sure which one you mean Ulco.
In one of them if you use only one fuzzy zone option it is easy to use as a negative mask.
After  i saw how little i know about this node i wanted to see it more detailed Ulco

[Dune]

Well, like in the noise variation of cloud fractals, or constants, or color adjusts, or smoothing option in surface shader...

[rossworx]

Thanks, everyone. BobbyStahr provided a solution (thanks!) which I'm still attempting to implement in new projects, not always with success. I try to allow a fuzzy zone that would let fewer trees (in this case) approach the shore of the water, by making the total of the zone and the 'hard edge' of the allowed area reach just above the water level. I'm also trying to get my head around some of the other posts here; but I'll keep working on this. Much appreciated -- and I'm glad my inquiry initiated some discussion!

[bigben]

The main thing you need to remember is that a mask/density shader for populations works with numbers. Just because you can't see any colour when you apply a mask to a surface shader doesn't mean that objects won't be placed there, and just because something looks white doesn't mean that the full density off objects will be placed. To be absolutely sure of not placing an object in a particular place you need to know that the mask will have a value of 0 at that point so, to be absolutely sure of not placing a tree in a lake you must start with a minimum altitude just above the water line.

[bobbystahr]

Thanks, everyone. BobbyStahr provided a solution (thanks!) which I'm still attempting to implement in new projects, not always with success. I try to allow a fuzzy zone that would let fewer trees (in this case) approach the shore of the water, by making the total of the zone and the 'hard edge' of the allowed area reach just above the water level. I'm also trying to get my head around some of the other posts here; but I'll keep working on this. Much appreciated -- and I'm glad my inquiry initiated some discussion!

My pleasure, happy it worked for you

[Stranded]

First off a Distribution shader has to go through the blend by shader switch to work.
I copied and pasted the one you included to use for the population and set it so it would work(see the .tgd attached)
re: Surface and Distribution shaders...It's generally better to use only one as your distribution I find, and for me it's the Distribution shader through the Blend /Mask input.
I adjusted your .tgd to reflect good distribution methods for surface and objects and made the coverage and coverage area much larger/denser.

Thank you bobbystahr. I know this is an old one but this post helped me tremendously get past an obstacle with object placement I was having!