Fog?

[voon]

Is it atm possible, to do some interesting, swirly fog? I.e. not just a general haze across everything .. I'm talking of things like a Ship coming out of fog etc? Or is this the same as fire and smoke in Octane 3?

[grimm]

Yep, this is a Octane 3.0 feature. There used to be a way to modify the fog but it was taken out because it didn't work very well. In 3.0 we will have OpenVDB which should be able to do this easily.

[voon]

OpenVDB? Never heard of .. but something to google for, thanks I have to admit, fog etc confuses me a bit, since in blender it's so tied into the app with cycles ... and it's confusing to handle. I'm looking forward to 3.x

[grimm]

OpenVDB will be really fun to play around with. I suspect that you would use the following workflow to use it. First you would create an object that represents the volume of the fog. This gets converted by Octane into a VDB grid. Now the fun starts in that you can then operate on this grid with other tools like OpenSL or other procedural tools to give it fluff or the swirls you want. Then the grid gets rendered as a volume when you render your scene. At least this is how I think it might be done, YMMV once 3.0 is out of course.

Jason

[voon]

Interaction with the objects would be cool ... like defining an object as physical hard thing (like with the physical attributes in blender) and just send it on an animated path through a fog volume ... and the fog "particles" would behave physically correct to swirl around the moving object. But maybe this is a b it crazy, because for realism, you'd have to calculate what kind of air swirls the phyiscal mesh causes

[grimm]

I don't see why you couldn't, it will depend on if Blender starts to support OpenVDB, especially exporting the grid. Maybe Jimstar can setup a Blender particle system to VDB conversion in the plugin?

[voon]

Hm .. I have no clue about these systems ... but the official Blender developers said openvdb is not part of blender and that there's only some patch, that isn't in yet:

<xxx>voon: sorry to disappoint, but it's not
<xxx>we have a patch in review that would add at least basic export from/import to the smoke sim, to avoid the horrendous space hungry point cache
<xxx>and we did some tests for gooseberry which worked in principle, but it was too close to deadline to actually use it
<xxx>oh yes, and also the patch adds a dedicated cycles render node for openvdb that avoids the crazy dense texture issues

And another said:
<yyy>voon: Hi, Blender had also not an Alembic exporter, Otoy wrote one themself
<yyy>voon: so if standalone support OpenVDB all plugins should support it too

Which leaves me confused (since I don't even know what all this stuff does ... all I know is that is somehoe need something called OpenVDB ).

I only update to 3.0, if blender plugin supports it fully.

[grimm]

Here is the full scoop on OpenVDB:

http://www.openvdb.org/

It's developed by DreamWorks and they have released it as open source. Basically it's a very cool method of creating, storing, and querying a sparse 3d grid of data. Good for volumetrics and a lot of other things too.

Like I said before you can always take a polygon object and convert it to a OpenVDB grid. For a lot of stuff this will probably be good enough and would be very easy to support in Blender. In fact all you would probably have to do is just mark the object as a volume, similar to how we mark objects for scattering, etc. The problem comes in when you need to have a particle system from Blender and then render it in Octane. It's probably doable but it's going to be a bit of work. It would just be easier if Blender already supported OpenVDB is all.

Jason