Is this a mistake in the manual.....?

[Markc]

Volumetrics, it states Distant and Env Light don't affect volumetrics.
Turning it on, it does.

 

[prometheus]

Seems so, distant and environment light should affect volumes, not sure how they got to that description.
Maybe they were talking about falloff settings...and for it to work properly..falloff is needed, but they do affect volumetrics to some degree.

Every other light I think has a default setting with inverse distant2 falloff applied, environment and distant Light has not.

Falloff will probably not work with environment lighting in lw 2019 anyway, no matter if you add fallof node in there.
Distant light falloff is tricky as well..with nodes, all this with the Global scattering foremost in mind.

If you for instance put a point light in the center of the scene camera view, turn off the intensity falloff, you wouldn´t have the volumetrics working.

 

[Markc]

Is there a setting (similar to flare2alpha) for volumetric lights..?
When rendering an F9 nothing shows in the Alpha channel for the lights.
If you add a buffer for vol light, you get a seperate render buffer, but doesn't have the full transparency.

final render

Alpha

Vol

 

[prometheus]

Is there a setting (similar to flare2alpha) for volumetric lights..?
When rendering an F9 nothing shows in the Alpha channel for the lights.
If you add a buffer for vol light, you get a seperate render buffer, but doesn't have the full transparency.

View attachment 154559final render
View attachment 154557Alpha
View attachment 154558Vol

Don´t know, have to check, but time is limited now and I have to run off and catch the bus and go for a new years dinner,
so Happy New year meanwhile.

 

[Markc]

Have a good one....

 

[lardbros]

Volumetrics, it states Distant and Env Light don't affect volumetrics.
Turning it on, it does.

View attachment 154555

Think that is an error... Have a feeling they were not going to allow those lights to affect volumetrics, but users/testers revolted, so they allowed it

As for the volume buffer not having an alpha. I think the renderer is now an additive renderer, so all (most) buffers can simply be added to the original render.
So, if you require your light volumes to be added in post, you just have to add them on top of your original render.

The help page below might be useful.

Back to Beauty - Rendering for Compositing - LightWave 2020

 

[prometheus]

Odd that developers would think of not allowing a distant light to not work with volumetrics like clouds or fog.
But perhaps they may have tried that as an incitament to use the new physical light instead.

 

[Markc]

Think that is an error... Have a feeling they were not going to allow those lights to affect volumetric's, but users/testers revolted, so they allowed it

As for the volume buffer not having an alpha. I think the renderer is now an additive renderer, so all (most) buffers can simply be added to the original render.
So, if you require your light volumes to be added in post, you just have to add them on top of your original render.

The help page below might be useful.

Back to Beauty - Rendering for Compositing - LightWave 2020

Thanks....
I have since rendered the volumetric pass separately, as an isolated light, not using the LW buffer system and it renders fine for comp in Fusion.

 

[Sensei]

Distant light has no position.
i.e. if you set light item -100m,-100m,-100m (XYZ)
it is giving no different render from setting it 0,0,0 (XYZ)
or 1km, 100km, 1000km (XYZ)

The distant light reacts to a change in the rotation of the light item.

(at least in LW 2020.0.2)

 

[prometheus]

That´s always been that way for the distant and physical sunlight light items position.

Distant light has volumetric distance, as well as pitch and heading direction for the rays.
Distant light has no falloff, physical sunlight do.
If it had no ray origin position(extracted to be used with pitch and heading) there would be no place from the rotation or pitch to work from at all.

Inverse distant falloff can be set within the nodal editor for the distant light, it is however together with global scattering with high aniostrophy, very slow in solving the noise when scattering lights, but that´s another story.

 

[Sensei]

HPB (Heading, Pitch and Bank) are rotations. Translated to ray direction vector (dx,dy,dz).
No need to have ray-origin to have ray-direction.

Raytracer is backward ray-tracer.
i.e. it does not cast ray from light source toward object,
it does it reverse, i.e. from surface which spot renderer is evaluating (Spot Info > World Position, in LW 2018+ Input > World Position), there is casted ray in -dx,-dy,-dz (which is reverse light sample direction from Light plugin class).
In lights which have limits like point light, any ray-lengths further than Distance(SpotInfo>WorldPosition,LightItem>WorldPosition) are discarded.
Falloff is calculated later (multiplication of light sample color multiplied by scalar etc).

Anyway, you have it on your disk
LWSDK/html/classes/light.html
You can read.. or not..

num = sample( instance, memory, ray, p, maxSamples, samples[], lightsamples[] )
    Given a position p in space, compute light samples.

       typedef struct st_LWLightSample {
          LWDVector direction;
          LWDVector color;
          double distance;
          double pdf;
       } LWLightSample;

    The light plugin fills in the samples information in the lightsamples array. Up to maxSamples samples can be stored in the array. This number is related to the maxilluminations value set by newFrame().

    direction
        The direction of the sample in world coordinates. It must be normalized.
    color
        The color of the sample.
    distance
        The distance between the spot being illuminated, and the light sample. A value of DBL_MAX indicates the source is infinitely far away, such as for Distant lights and other 'infinite' lights.
    pdf
        The probability distribution function of the sample.