Jeff Wagner

The File SOP supports dxf files directly.
Remember in Houdini, the File SOP can load in all kinds of geometry formats by extension and magic data.

e.g.: In the File SOP's path parm, use the file browser and find your .dxf file

To quickly see what extensions are supported, in the lower right of the File Browser is a very long string of supported extensions.

Yes very low resolution volumes.
After vdbcombine1, insert a VDB Resample SOP
Define Transform: Using Voxel Scale Only
Voxel Scale: 0.5
That will double the voxel resolution.

Then append a VDB Smooth SOP
Operation: Median Value (seemed to look the best here)
Iterations: 1

That gives you a smoother result for sure.

Tanto is right.
In the Pyro material, density volume renders into color and alpha.
Pyro contribution is emitting and it does not generate an alpha by design.

Yes to comp to convert pyro color to alpha and use that.