Bcf2vdb And the 'Fire' and 'Smoke' RGBA channels used by Arnold


I’m wondering if there is anyway to include the ‘fire’ and ‘smoke’ channels that Arnold uses in it’s interaction with TFD if you add an Arnold tag to the TFD container, when converting the .bcf files that TFD uses to an OpenVDB format using the bcf2vdb application?

Even the command line version states that only the float and vector channels are available, and TFD itself has the same list of channels checkable.

Is there a way to get the 2 RGBA channels included in the openvdb conversion? These channels make shading the fire so easy as a starting point!

Many thanks!!


It appears the ‘fire’ channel can be used as a BlackBody multiplier, but if the mode in Arnold is set to ‘channel’ rather than ‘blackbody’ there is a very strange ‘MineCraft’ result…nothing like when those settings are used with the TFD container, which then reproduces the ‘Physical + Multiple Scattering’ from the native renderer.

Same if you specify ‘smoke’ or ‘density’ in the ‘density’ channel of the openVDB - instant ‘Minecraft’.

It reports only ‘temperature’ in the ‘available grids’ for the Arnold Volume.

I’m getting some nice looks, just wondering if there is some setup I’m not familiar with that works better.

One issue for the blockiness may be step size

The RGBA output of TFD’s Fire and Smoke shaders cannot be written to VDB at this point. The shaders compute these value on-demand based on the stored volume channels. Arnold’s Volume shader can do the same shading computation although its parameters have to be setup differently to achieve the same results.

A generic guess for a reason of the blockiness would be that some intensity parameter is set to an extreme value, making the voxel boundaries visible. In order for the voxels not to be visible as Lego bricks, their values have to fade smoothly across contour edges.
I recommend contacting Autodesk support regarding the shading options and parameters of Arnold, though, they know them best.

Thanks very much for all replies, indeed it seems that adding a few nodes and playing about in the network of the volume shader can do all kinds of magic with just a ‘temperature’ channel :slight_smile:

Amazing integration of the plugin with Arnold and C4DtoA, getting the exact look is sooo much easier than my experience with Octane, though it too produced some great looks!