vray 6.1 clouds shadow problem

[Jiri.Matys]

Hi,

I have this problem with shadows from clouds, see images. Without clouds, I have nice image, with clouds I have almost no light in a scene. I dont have ground shadows enabled! When I lower the density of the clouds to 0.1 or so scene is lit normaly so there are still shadows or some another problem.

[hermit.crab]

Quoting the docs: "Ground shadows – When disabled, the entire scene is covered by a single shadow or fully illuminated depending on whether the sun is blocked by a cloud at the current camera position."

[Jiri.Matys]

oh, ok, didt look at the docs for this one, sorry.

Problem is when the sun is low and clouds density are 0,5 or higher ground is covered with shadow permanently because clouds covering all the horizont and you have tu put sun much higher. Not sure if this is good. In real life clouds are different with a distance, on the left side there can be big cloud and on the other side there is no cloud at all. My point is vray clouds are homogenous over all area so with density 0.5 or so there will be always shadows with low light.

[^Lele^]

If you need that kind of detail, it's unlikely a simple approach like that of the sun clouds will ever be enough.
You should look into at least mixing the approach with hero clouds made in Phoenix, or analogous method.
Then you'll be able to have the center pieces animate as fluids, rather than noise fields, and shadow the scene correctly, while the background clouds help filling in the sky.

[dlparisi]

oh, ok, didt look at the docs for this one, sorry.

Problem is when the sun is low and clouds density are 0,5 or higher ground is covered with shadow permanently because clouds covering all the horizont and you have tu put sun much higher. Not sure if this is good. In real life clouds are different with a distance, on the left side there can be big cloud and on the other side there is no cloud at all. My point is vray clouds are homogenous over all area so with density 0.5 or so there will be always shadows with low light.

In a quick test I did you can simply add a 2nd matching sun to the scene and uncheck all of the Affect diffuse, specular, etc.,. Then check clouds 'on' for this sun and turn clouds 'off' for the original one. You should also turn the original sun to "invisible". The new render will use the 2nd sun for all reflections and backgrounds but lighting and shading will rely on the first one. May be an option for you.

[^Lele^]

Outright clever idea!

[dlparisi]

Thanks. BTW - my first thought was to just turn off the second sun with clouds and specify that sun node in the VRaySky bitmap of the dome light/environment map but I noticed that specifying the sun node removes all clouds from the bitmap. Even weirder it doesn't show the clouds but KEEPS the occluded shadows of these clouds. Do you know if this is this a bug or intentional behavior?

[^Lele^]

Umh, possibly a bug.
Will ask and report (likely tomorrow).

[Jiri.Matys]

In a quick test I did you can simply add a 2nd matching sun to the scene and uncheck all of the Affect diffuse, specular, etc.,. Then check clouds 'on' for this sun and turn clouds 'off' for the original one. You should also turn the original sun to "invisible". The new render will use the 2nd sun for all reflections and backgrounds but lighting and shading will rely on the first one. May be an option for you.

oh, cool, thank you.

[rodri_garcia]

I would like to see an option to just stop the clouds affecting the lighting. if there is a cloud front of the sun or not.

[bruce_hart]

I agree with rodi_garcia. I find sometimes the most artistic looking clouds are in the 0.6-0.7 density range. Trouble is, at this point the sun lighting can dim considerably. I then experiment with changing the X/Y position of the clouds to get the sun shining again, but it would be better to have an option to not affect lighting

[liddil101]

In a quick test I did you can simply add a 2nd matching sun to the scene and uncheck all of the Affect diffuse, specular, etc.,. Then check clouds 'on' for this sun and turn clouds 'off' for the original one. You should also turn the original sun to "invisible". The new render will use the 2nd sun for all reflections and backgrounds but lighting and shading will rely on the first one. May be an option for you.

I ran into the exact same issue while rendering an animation of a sunset. The sun kept going behind the clouds causing a "flicker" look to the animation since the sun was passing through so many clouds. I adjusted the cloud settings over and over with all kinds of variations and the sun still passed through clouds making the light flickering happen as the animation is pretty quick. Once i did what you did with the same settings, it animates perfect. It would be nice to have an option for the sun to "pass through" clouds as some kind of override.