Post Volume Effect Fog not working with refractive materials

[tombyrom]

Hello,
The Post Volume Effect Fog does not work with refractive materials, glass for example. All other post-processing effects work, is this a bug?
Thanks
Tom

[larsgehrt]

Can we see your material?

[paride4331]

Hi tombyrom,
I can replicate your issue and have sent my test to the development team.
Regards
Paride

[paride4331]

Hi tombyrom,
At the moment the postfx fog is using the depth buffer for such an effect. When a specular object is present in the scene, it holds a depth value from the camera, so the postfx fog kernel will think the ray stops there. Consequently the postfx fog effect is lighter.
Maybe a work around is to isolate the mesh with Specular and add them later in post.
Regards
Paride

[HHbomb]

It could be cool to add "unseen by zdepth" as we have "unseen by camera" ?

[tombyrom]

Thanks Paride, however, I had to stop using the effect because of lack of control over the start distance. And on very large scenes 2-5 kilometers + it does not work well enough, too much in the foreground and mid-ground are exposed to the effect even with max values. The only way around this would be to scale the scene down far smaller than physically accurate which I don't want to do. Hopefully if they are using the depth buffer it will be easy for them to implement a start distance in the future to solve this.

[larsgehrt]

Hey Tombyrom,

I also use this effects, and it does take some adjustments to be able to use it correctly. On some scenes it does work though.

Se example. Foreground is clear and in the background it works like intended.

[tombyrom]

Nice image! I agree it does work fairly well on yours, I have a similar scene but in my example it does not work great. It is exaggerated as it is an aerial shot so even the foreground elements are not very close to my camera. The scale of the initial islands is 5kilometers, the water on the horizon goes on for another 30 kilometres. With Octane we cannot increase the extinction scale past 10000 meters and the fact we have no start distance control, as you can see my whole scene is covered in fog.

If the scene was much smaller with foreground and midground elements closer to the camera it would be less obvious (perhaps like with yours).

I also use Chaos Vantage and they have start distance on all their fog parameters and it works great for this type of fog.

Attaching a z depth pass from Octane which allows you to have control over the maximum depth, I have set it to where I would want fog, now compare that to the furthest settings on the post effect fog pass, its very different!

I can probably do some comp with the pass and gradients and change the gamma etc etc, but I hate having to comp stuff when it could just be done by the engine as it is just wasted time IMO

[larsgehrt]

yes i see your problem, I would use a Zdepth pass to create the desired fog in that scene then.