V3 Cloud Radius Limits

Started by WAS, June 26, 2018, 02:36:14 PM

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WAS

What exactly is happening when you take a v3 cloud and up it's radius beyond, what I assume is it's soft-max? I notice the cloud gets "brighter", but unsure why, what is happening when v3 cloud radius gets too large?

Oshyan

What kind of Radius values are you trying? V3 clouds are localized by design and shouldn't be used in really large-scale (e.g. global view) situations, but they should work up to reasonably large scales still.

- Oshyan

pokoy

Quote from: WASasquatch on June 26, 2018, 02:36:14 PM
What exactly is happening when you take a v3 cloud and up it's radius beyond, what I assume is it's soft-max? I notice the cloud gets "brighter", but unsure why, what is happening when v3 cloud radius gets too large?

The cloud propably gets brighter because the voxel resolution decreases and you are losing detail. You could try to increase voxel count and see if it helps.

WAS

Quote from: pokoy on June 27, 2018, 05:36:49 AM
Quote from: WASasquatch on June 26, 2018, 02:36:14 PM
What exactly is happening when you take a v3 cloud and up it's radius beyond, what I assume is it's soft-max? I notice the cloud gets "brighter", but unsure why, what is happening when v3 cloud radius gets too large?

The cloud propably gets brighter because the voxel resolution decreases and you are losing detail. You could try to increase voxel count and see if it helps.

Thank you, that makes sense.

And my scale is 50000 so there is no sky on the horizon which is a bit annoying with any base localized clouds.

Oshyan

50,000 is the default though...

- Oshyan

WAS


Dune

Just use v2 for distant added clouds and/or move the cloud.

WAS

#7
Quote from: Dune on June 28, 2018, 01:21:00 AM
Just use v2 for distant added clouds and/or move the cloud.

I'm just trying to keep render time down. At any point V3 intersects with V2/3, or something obscures direct lighting, things slow down on V3. If I use a V3 with layers and super light 2D cloud for high alt like the cirrus-cirrocumulus setup, I can achieve a full real-world cloud setup that renders relatively fast.

Dune

You can also mask out the v3 cloud area from the v2.

WAS

That's an idea though I feel like it would create a Halo of godrays around the v3 boundary creating lit haze in the distance instead of Darkness.

WAS

Did some testing with that note about voxels, and increasing voxels to compensate for radius actually makes the clouds brighter, instead of normalizing them like they are at base radius. I am assuming this is the lighting model that this is coming from?

pokoy

Quote from: WASasquatch on July 02, 2018, 01:23:18 AM
Did some testing with that note about voxels, and increasing voxels to compensate for radius actually makes the clouds brighter, instead of normalizing them like they are at base radius. I am assuming this is the lighting model that this is coming from?

It's hard to say what increasing voxel count will do, it's a bit of a trial and error, sometimes lower values can look better, but generall higher values will be more accurate to what actually happens in the cloud in regards to illumination. For example, it could be that your original cloud had too few voxels, and you're getting a more accurate result now...

One thing to keep in mind is that clouds are typically much less stretched our over world y-axis, meaning that you could end up with only a few voxels for their vertical span, easily leading to too little illumination information to be accurate. It would be cool if there was a multiplier for voxel count for y-axis only.

WAS

#12
Quote from: pokoy on July 02, 2018, 12:41:13 PM
Quote from: WASasquatch on July 02, 2018, 01:23:18 AM
Did some testing with that note about voxels, and increasing voxels to compensate for radius actually makes the clouds brighter, instead of normalizing them like they are at base radius. I am assuming this is the lighting model that this is coming from?
...

One thing to keep in mind is that clouds are typically much less stretched our over world y-axis, meaning that you could end up with only a few voxels for their vertical span, easily leading to too little illumination information to be accurate. It would be cool if there was a multiplier for voxel count for y-axis only.

That seems to be a struggling problem with clouds and density with lighting. I've been trying to create a cloudy day cloud setup like in WA and so far am not able to get clouds lighting to interact with each other appropriately. Trying some stuff now to see if I can obtain the look with a single cloud layer and a custom density setup but so far doesn't look like it's working either in what is rendering.

Seems clouds don't allow enough light to actually pass through them. For example, even pretty thin and bright clouds end up making your terrain as dark as twilight hours.

Another issue I've been trying to figure out is why there is no ability to adjust, basically, the "specular" roughness of clouds. Any time the sun is in the scene you get a very hard bright spot from the sun, which doesn't cascade over the clouds to create a "bright region" rather than a spot. Even thin clouds blot the sun very well and light the whole cloud area rather than beaming through, while the clouds themselves produce enviro light for the ground to compensate for the sun being blocked as the whole region is glowing from the sun at a direct observable angle

Edit: Hmm, ironically, upping the cloud radius from default stretches this "spot" created by the sun it seems. Doing a test render. Edit 2: More of an illusion in the preview.