I needed the fire to collide with the second wizard in the scene, for this to occur, the emitter particles need to collide with the geometry of the second wizard.
Improved pyro
To this, a collision calculation node is used on the geo of the second wizard.
This creates a kind of shell around the model of the second wizard, which means that if any particles were to collide with the vop they would bounce off and in the correct direction.
Superior collision detection.
Now within the popnet, the emitted particles collide with the geo and change direction accordingly.
This did have the desired effect for the stream of particles representing the spell. However, as you can see, when I apply the pyro to the volume, it treates the collision shell on the second wizard as a fire source! Meaning he was burning from frame 1.
It took me a couple of days to sort out this issue, where I made used of a houdini forum.
The solution came from a very kind person on the forum who told me I needed a “dopio” node to filter out parts of the dotnet.