I am using a panoramic HDR image as the principal direct lighting source for my scene at the top of the Empire State Building, as well as the visible background. To increase the sense of space in the scene I wanted to add some Atmospheric Perspective (aka haze) by using Volume Scatter at a low Density value. However, I found that doing so completely negates my Environmental Lighting, and incidentally also kills the Sun lamp I use to sharpen up the cast shadows. I’ve used Volume Scatter before but with a mesh light as the main source – tests show that this seems to be the only usable method of lighting within a Volume Scatter volume, but a mesh light doesn’t even begin to match the lighting scheme I’ve already designed.
Am I missing some setting or adjustment to allow the desired lighting plan to work properly? I tried many reconfigurations of the scene to no avail. Is there another method of introducing haze for Cycles? I’d rather avoid compositing or use of Mist, which I find looks very artificial.
Did you add the volume scatter to the entire world?
The sun is always infinitely far away. If you add Volume Scatter to everything, the light will have to pass through an entire “universe” of volume scatter before it reaches your scene - meaning it doesn’t reach it at all.
It’s preferable in most cases to enclose the scene in a finite box with Volume Scatter added to it and remove Volume Scatter from the world - if the scene allows.
I tried both, Ikari, and even mounted a “Scatterbox” Volume Scatter filter on my Active Camera in looking for a way around the problem. I realized the “infinite distance” problem when using the VS in the World parameters, and so used both a sphere enclosing the scene and the filter method I mentioned. No matter the Density value, either, any amount of VS kills the lighting.
I just tested this in 2.78rc1 and got the same results – in fact, Volume Scatter in 2.78 seems glitched, as it does not operate in the same manner as in 2.76.
Have you tried increasing the light strength of the background ? Bring it up until it matches the light you want but retaining haze/atmosphere. Don’t forget you can make the background light stronger and control separately how it looks to the camera.
A logical suggestion, Bunc, and I thank you, but unfortunately also a no-go. I pushed the Env. Light value to 10,000 and more with absolutely no change in the lighting on the scene when viewed through Volume Scatter. Same result (or lack of result, I guess) by boosting the Sun lamp’s value. By comparison my normal Env. Lighting value for the scene is 10.
My visible background is the same image I use as the HDR lighting source, but mapped to a sphere & set for Emission (value = 1.3). Since it’s essentially a mesh light, it does work within the VS, but does not give the same results as using the image in the World parameters, where I can jack up the value as needed without it being visible to the camera. I also tried using two “nested” spheres – one for lighting, one for visible skies – but the result was not as satisfactory as using the World to light the scene. I’d rather do without the VS haze, to be honest, if I have no other option.
I usually enable Multiple Importance only for my main lighting source to avoid firefly infestations, so only for the “World light” in this case, but in my attempts to remedy the problem I did try switching it on & off, to no avail. Same for the Sun lamp.
Partial and mysterious semi-solution: If I enable Ray Visibility>Camera for the “filter box” placed on the camera (and shaded with ONLY Volume Scatter), the VS no longer affects the lighting. My assumption is that as long as this filter object does not enclose any other objects in the scene, their lighting will not be effected, either, so I will have to use it carefully.
Thanks for your suggestions, guys, I appreciate your taking the time.
Ironic conclusion: Volume Scattering is not a very good way to introduce atmospheric perspective, at least not in my scene, as it strongly suppresses all the subtle highlight and shadow structure I struggled to preserve in the lighting design, making the lighting very flat and rather muddy, even for parts of the scene relatively near to the camera. While this might be acceptable for situations like fog or suspended dust, it’s too heavy-handed for a bit of atmo haze. AND it generates a metric tonne or six of the dreaded FIREFLIES! This with a density of only .002 max.
