My Golden Forest

Started by Valentina, July 28, 2018, 04:49:36 PM

Previous topic - Next topic

Dune

I think sharpness increases the difference between cloud and no cloud, the contrast sort of. So, logically in denser cloud you'd have more visible godrays, but it decreases in other areas. You might as well leave sharpness very soft (or use no cloud fractal at all and extremely low sharpness) and increase overall density of the cloud for better godrays. There seem to be differences in strength of godrays in stuff like sun glow amount and power and maybe light propagation and scattering.
And it's faster to use v2 cloud than v3.

Valentina

Quote from: Dune on August 02, 2018, 01:23:08 AM
I think sharpness increases the difference between cloud and no cloud, the contrast sort of. So, logically in denser cloud you'd have more visible godrays, but it decreases in other areas. You might as well leave sharpness very soft (or use no cloud fractal at all and extremely low sharpness) and increase overall density of the cloud for better godrays. There seem to be differences in strength of godrays in stuff like sun glow amount and power and maybe light propagation and scattering.
And it's faster to use v2 cloud than v3.

That's what I did, I think you're right.

WASasquatch, this is the difference:
[attach=1]

Oshyan

It's entirely possible I misunderstand (to some degree) what Edge Sharpness does (Matt is the only one who fully understands everything in TG), but I understood it the way Ulco explains: the difference between cloud and no cloud. The visible (light) area of a sunbeam is not "more cloud" and the dark (shadow) area is not "no cloud", they are simply "lit cloud" vs "unlit cloud", so I would not think they should be *directly* affected by sharpness. I.e. I don't think the sharpness should be directly influencing the sharpness of beams. *However* it could easily have an effect on beam sharpness anyway simply due to making the normal variation in the cloud structures sharper and more defined, sort of increasing overall contrast within the cloud volume, which would make the bright bits brighter. It's not making the edges sharper per-se, but increasing contrast as a byproduct.

If all that is correct, then it's not a bad idea to increase edge sharpness somewhat for "god rays", but it's neither necessary nor ideal for every scene. It's just something you can increase for some added effect.

I'll see if I can get Matt to verify any of this.

- Oshyan

Matt

In this situation my recommendation would be to leave "edge sharpness" at 1, or at least not too far from the default. Instead, I would change "cloud density". For the most part it will have a similar effect on the appearance of the cloud, but the reason for preferring cloud density over edge sharpness is this: the automatic sampling adjustments that derive from "ray march quality" are more strongly influenced by cloud density than by edge sharpness. In other words, if you set cloud density very high, the render quality will adjust accordingly to keep the noise levels the same, but if you do this with edge sharpness it will not increase sampling to the same degree, meaning that you might have to increase ray march quality much higher than is typical for most scenes.

My general advice would be to use edge sharpness to adjust the edges of distant cloud or clouds that already have fairly well defined edges. For thinner fog and mist effects I would always choose to control the density with cloud density.

For more details - more than you probably ever want to know! - there's this:

https://planetside.co.uk/forums/index.php/topic,24572.msg249771.html#msg249771

Just because milk is white doesn't mean that clouds are made of milk.

Matt

#34
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" in the following way: it is multiplied by "edge sharpness", then clamped so it never exceeds 1, and then multiplied by "cloud density".

Both "edge sharpness" and "cloud density" have the ability to change the density at the edges of clouds. However, because of the clamping, only "cloud density" can change the density everywhere.

Regarding so-called god rays, the reason these two settings affect them is because they affect the density of the medium, therefore affect the apparent visibility of the medium, which affects the visibility of the god rays.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Oshyan

Thanks Matt, so it's basically what I thought, but explained much more clearly and in greater detail. Cool. :)

- Oshyan

WAS

#36
Quote from: Oshyan on August 02, 2018, 05:51:03 PM
It's entirely possible I misunderstand (to some degree) what Edge Sharpness does (Matt is the only one who fully understands everything in TG), but I understood it the way Ulco explains: the difference between cloud and no cloud. The visible (light) area of a sunbeam is not "more cloud" and the dark (shadow) area is not "no cloud", they are simply "lit cloud" vs "unlit cloud", so I would not think they should be *directly* affected by sharpness. I.e. I don't think the sharpness should be directly influencing the sharpness of beams. *However* it could easily have an effect on beam sharpness anyway simply due to making the normal variation in the cloud structures sharper and more defined, sort of increasing overall contrast within the cloud volume, which would make the bright bits brighter. It's not making the edges sharper per-se, but increasing contrast as a byproduct.

If all that is correct, then it's not a bad idea to increase edge sharpness somewhat for "god rays", but it's neither necessary nor ideal for every scene. It's just something you can increase for some added effect.

I'll see if I can get Matt to verify any of this.

- Oshyan

Recently Matt explained it and it sounded much more advanced, actually isolating the cloud boundaries/edgesbased on the fractal. Cloud-no-cloud sounds just like density.  Density also exponentially changes the intended look.

Valentina

I'll take some time to study all what you've said :) thank you!

WAS

Quote from: Valentina on August 02, 2018, 05:05:12 AM
Quote from: Dune on August 02, 2018, 01:23:08 AM
I think sharpness increases the difference between cloud and no cloud, the contrast sort of. So, logically in denser cloud you'd have more visible godrays, but it decreases in other areas. You might as well leave sharpness very soft (or use no cloud fractal at all and extremely low sharpness) and increase overall density of the cloud for better godrays. There seem to be differences in strength of godrays in stuff like sun glow amount and power and maybe light propagation and scattering.
And it's faster to use v2 cloud than v3.

That's what I did, I think you're right.

WASasquatch, this is the difference:
[attach=1]

So there is indeed more god rays (contrary to discussion), and also seems to be more highlights on the foliage itself which is odd.

Oshyan

Matt's explanation above matches my understanding. I was using a simplified explanation (intentionally), but it works just as I thought: by influencing the transition area between cloud and no cloud (the "edges"). The end result is that it *does* have an effect on godray intensity but only because it effectively changes the density; changing the density directly has a similar effect and is a better approach.

- Oshyan

WAS

#40
Quote from: Oshyan on August 03, 2018, 04:30:33 PM
Matt's explanation above matches my understanding. I was using a simplified explanation (intentionally), but it works just as I thought: by influencing the transition area between cloud and no cloud (the "edges"). The end result is that it *does* have an effect on godray intensity but only because it effectively changes the density; changing the density directly has a similar effect and is a better approach.

- Oshyan

I think what's being forgotten in this whole scenario, that I tried to iterate from the beginning is the silver lining effect. This creates "whiteness" and in a soft cloud, helps these godrays have a base and fade rather than relying entirely on density, which isn't realistic for volume....

You can plainly see these effect in the difference between 100 sharpness. It really can't be argued, it's plainly there. Density will exponentially effect this effect, but usually just upping density, will also of course give you denser clouds and change the whole look. That's why a combination of sharpness and density works great, as seen in results rather than talking technical...

A sharpness of 1, needs a bit higher density, creating thick fog. What if you don't want thick fog? One look may be a good trade off for someone else, but my be directly what they're trying to save from.