Bubble trouble

Bubble trouble

Hi guys
In the image below you can see a problem I'm having with some bubbles I'm using a particle emitter to generate them and in the interests of keeping render times short I'm using the membrane shader for the bubbles. I've also got fog turned on to simulate the change in visibility under water. The problem is that the membrane shader seems to not take account of the fog and so the view through the bubbles looks too clear. I seem to recall there was some problem with fog but I thought that had been fixed? I've tried messing around with all sorts of render tag settings but no luck so far. Would appreciate any thoughts on how to fix this.
cheers
Daryl

Hi Daryl!
maybe you could try a faux volumetrics approach as a workaround... please check the attached example (lot of work to do but it should give you an idea)

demo renders with camera light on/off

cheers,
Alessandro

Hi Alessandro, thanks for having a crack at that. Unfortunately I don't think that is quite going to do it as you don't get the same feeling of depth that the fog gives and the render times are way longer too which isn't great for an animation. I'll have to try something else. Will let you know if I work it out.
Appreciate the effort!
cheers
Daryl

Just checked the feature list for v5.6 and one point listed is:

fixed rendering bug with fog and transparent objects

Martin, can you elaborate please as there still seems to be a problem. Thanks.

Hi,
could you please send me the clown fish scene via email. That indeed doesn't look correct.

Bye
Martin

It's on it's way. Thanks.

Hi,
thanks I got your file. The problem was the fog start value. If there are transparent object in the scene please use a fog start value of 0. To compensate the lower fog start value you have to lower the fog density too. But then it should work.

Bye
Martin

Hi Martin
Thanks. That kind of works but it seems like a bit of a workaround? It also doesn't allow you to have a clear foreground which helps create the illusion of depth. Any chance this can be improved in future? Are you planning on introducing multipass render options at some point (i.e. ability to render seperate channels such as z-buffer, diffuse, specular, etc.)? That'd be really useful and I imagine it would address issues like this?

cheers

Daryl

Hi,
yes, it is more a work a round at the moment. I will try to address that problem soon but I currently can't promise it for 5.7.

A Z-Buffer won't help in that case since always the depth of the first intersection is in the Z-Buffer. But in case of transparent object the ray doesn't stop there.:wink:

Bye
Martin