Dispersive Glass in a Misty Forest

[kintuX]

Hi, i'm faced with a problem of balancing (optimizing) the settings & values for what seems to be far more tricky scene than expected.

Scene description:
- Couple of trees (Leaves are Glossy Translucent, other materials Matte)
- Sphere (Glass with dispersion)
- Fog (Homogeneous Volume)

Problems:

1. Noise & fireflies are almost impossible to clear out. (eg. 4K crop)

2. Then Suggested clamping darkens the glass too much, glass becomes orange, yet in 4K fireflies are still present.
(A Thought - Could supersampling be implemented?)

3. Using Fog (Volume with scattering) unrealistically brightens the scene (even with Clear volume)

Exemplary scene 'GlassTreeFog' (link) also shows extra & different problems

I assume it's combination of Volume and Single faces (normals) looking the wrong way & I should thicken all the leaves... insane
But in this case noise & fireflies got cleared. Seems that lots of mesh intersections are the cause (tree crowns with glossy translucency in the bigger scene).


Oh, and another question that i'm interested in since problems seem to be relative to scene complexity: Which Light Strategy is used in the engine?

IIRC, some are heavy dependent on lights with the single setting that can cause huge headaches & it's slowly getting to me or it got me already.
Any help to better understand & advice on how to tackle this is more than welcome.

[Dade]

3. Using Fog (Volume with scattering) unrealistically brightens the scene (even with Clear volume)

The volume settings may be wrong: adding a volume usually makes the image darker. Have you set any absorption ?

I assume it's combination of Volume and Single faces (normals) looking the wrong way & I should thicken all the leaves... insane

There is no need, just assign the same interior and exterior volume (i.e. air) to leafs and the normal direction will not matter. I assume they are modeled as a single face polygons.

In general is hard to make any comments without having access to all materials/volumes settings. A simple test scene with the materials/volumes used would help.

Also rendering at 4K takes forever due to the huge number of pixels.

[kintuX]

3. Using Fog (Volume with scattering) unrealistically brightens the scene (even with Clear volume)

The volume settings may be wrong: adding a volume usually makes the image darker. Have you set any absorption ?

I assume it's combination of Volume and Single faces (normals) looking the wrong way & I should thicken all the leaves... insane

There is no need, just assign the same interior and exterior volume (i.e. air) to leafs and the normal direction will not matter. I assume they are modeled as a single face polygons.

I really overlooked that. Thanks.

In general is hard to make any comments without having access to all materials/volumes settings. A simple test scene with the materials/volumes used would help.

Yeah it's posted above & here for commodity
Exemplary scene 'GlassTreeFog.zip' (~30MB)

Also rendering at 4K takes forever due to the huge number of pixels.

Yup, why supersampling would come in handy... but more of a thought for later, when denoising is suppose to come to the table.

[kintuX]

There is no need, just assign the same interior and exterior volume (i.e. air) to leafs and the normal direction will not matter. I assume they are modeled as a single face polygons.

This doesn't resolve an issue. Still get transparent leaves.
While here Fog doesn't brighten the scene. Need to investigate a bit more.


Still wish to know about Light Strategies used.

Edit1:
The transparency issue appears to be less obvious with CPU but is still present. (& faster too )

[Dade]

Still wish to know about Light Strategies used.

The default is LOG_POWER: light sources are sampled proportionally to the logarithmic of their power.

[Dade]

I will post my finding ... when I find something.

First, multi-scattering !!! Disable it, it is a suicide performance wise.

[Dade]

GlossyTranlucent material is a huge overkill for rendering thousands of leafs.

I would use simple Glossy material with the same properties but a different opacity map: at the moment you are using a mask (0 or 1 values), I would use a map with a slight green transparency to have the GlossyTranlucent look (at a fraction of the cost).

With this type of change, your scene runs about 2.5 faster on my GPU.

[Dade]

I have also set u/v roughness to 0.1 to make the leafs a bit more "shinny" (also removed the anisotropic U/V difference) and increased the sun/sky gain by 4. This is a 30mins rendering:

without any kind of clamping. It doesn't seem necessary at all in this scene.

I will then re-enabled volumes and check what is going on when I'm back.

[kintuX]

Still wish to know about Light Strategies used.

The default is LOG_POWER: light sources are sampled proportionally to the logarithmic of their power.

Thanks.
I couldn't find where to set it differently (to Uniform) or where it's defined/configured (nothing in .cfg).

First, multi-scattering !!! Disable it, it is a suicide performance wise.

Yup, i have a tendency for self destruction...
Either way, some day, one day, i'm gonna end up a pile of ashes, so why not go all the way while i can & am able.
At least for others, to see and choose, experience - to be or not to be, if walking the same path, making similar steps, mistakes. It's how "..." made & is making me.

GlossyTranlucent material is a huge overkill for rendering thousands of leafs.

I would use simple Glossy material with the same properties but a different opacity map: at the moment you are using a mask (0 or 1 values), I would use a map with a slight green transparency to have the GlossyTranlucent look (at a fraction of the cost).

With this type of change, your scene runs about 2.5 faster on my GPU.

I also have a scene with leaves modeled so no mask is needed - it's all a part of comparative study case: Geo VS Mask/Alpha (more user work VS more machine work).

I have also set u/v roughness to 0.1 to make the leafs a bit more "shinny" (also removed the anisotropic U/V difference) and increased the sun/sky gain by 4.

'Shinny is Plastic' in my book. But nevermind. I'm also going to introduce iridescence (thin film) at later time when (if) it becomes available.

without any kind of clamping. It doesn't seem necessary at all in this scene.

Indeed, i was also nicely surprised when it worked out without.

I will then re-enabled volumes and check what is going on when I'm back.

This single face transparency in volume is the only wonder left in this scene.

Thank you very much for everything.
I really appreciate your dedication, giving me motivation to grind on.


PS


It is the 'plastic' look i wish to avoid & upgrade for 'naturalistic' high end demands of 4K+ where details became so prominent that, if done bad or wrong they can diminish all the work (the rest 90-99%) that got an artist this far. Also, without use of the post-cinematic effect to achieve spectacularity which is leading right back to 'fakeness', fictive delusion. (ref. "Goodbye Uncanny Valley" from Alan Warburton @ 6:53 min).
Machine times are not of the essence here.


'A very thin, slilppery path, leading over the ridge and to the top is where most of them fail.'

... or maybe i'm simply too ambitious, overwhelmed by grandiose delusions.
Hmm...

well, day waits for no one

read you latter

[B.Y.O.B.]

Light strategy is not yet exposed in the addon and not set as property because we use LuxCore's default.
You can find how to set it here: https://wiki.luxcorerender.org/LuxCore_ ... t_Strategy