I work for a small ministry doing the VFX and motion graphics for a documentary. A large section of the documentary deals with the Old Testament sanctuary and so I've had to design a pillar of cloud and a pillar of fire. My background in 3D is Blender, and the majority of the work is done there. However, on occasion we have had to bring other software into the pipeline such as Lightwave and now, Houdini. The pillar of fire I decided would be best done in Houdini, and rendered out to be composited in with the animations from Blender. I've worked out getting the camera moves between the software, and I have made the tent a matte object, but being so new to the software, I don't fully understand how to do what I need to in regards to the actual fire. I know just enough to get close, but I'm running into some issues.

If you look at the attached images, there's an example of how it should look, and how it's currently looking. The physical size of the bottom part is perfect, and fits onto the model of the tent brought in from Blender perfectly. But then the fire expands out and almost looks like water, with a whirlpool or something inside. I would like the entire pillar to look like that bottom section. Any ideas how I would go about doing that?
I'm using the Apprentice version of Houdini right now until I can be 100 percent sure that I have the effect nailed, at which point the ministry will purchase a license. Thanks a lot for taking a look!

-Chris

A Pillar of fire is surely not a normal phenomenon. Lets call this an act of God where you are in control of the forces, gravity, whatever it takes. A non-physical approach is warranted. Need to create a long shaft of fuel emitting fuel and velocity.

See the example file with notes.

I just created a curve, then turned it in to a tube with velocity and then ran the smokeless fire tool on it. No look dev done at all other than to set up the heat ramp in the Pyro Shader to get you rolling.

Feed in any curve you want in to the network.

Note that you can also add the Gas Curve Force tool from the Container Tools shelf applied to the backbone initial curve if you want even more shaping control over the fire. To make it suck more along the curve if you want.

Thanks a lot Jeff, much appreciated. Going to dig into that now.

I'm having problems rendering the file you uploaded. I get just a black screen, but if I view the alpha channel, I can see the box shape just fine. Any ideas?

Hmmm that is very interesting.

In the Pyro Shaders, Smoke Field tab, you have to clear the Density Volume parameter, remove the “heat” field reference.

With that clear, you can render the shaft of fire and start the look dev of the effect.

Even though I set the density contribution of smoke to 0, the shader still calculates the field and forces mantra to cull opacity based on this field.

Removing it allows the fire to render as a pure emissive Ce object that uses no lights.

Apologize for that.

I updated the hip file in the above post and added a new test render with just the illumination through a volume light.

Note that I cut the resolution of the sim down by half. Go to the Pyro Object DOP and remove the *2 from the division size to sim at the original resolution. Adjust the sim resolution to suit your needs.

You may want to add a Volume Light to the Pyro Import object if you want this fire shaft to properly illuminate other objects in the scene.

Just select the pyro_import object then press the Volume Light tool from the Lights and Camera shelf. Now you can control the light cast from the fire shaft from this Volume light.

Fyi it uses pre-generated photons cast in the volume to act as many little light sources. No need to worry as the photon generation is set up to be automatic for every frame.

Works great, this definitely gets me headed the right direction. Thank you!

Hello guys.
jeff your project really helped me.
but i have an important problem in houdini's fire shader.
distribution of heat and temperature field isn't what i expect.
for example in attached image i want to have more heat and temperature field just in red ellipse but i don't have any idea how to do that(playing with heat and temperature doesn't help).
i search for something like P attribute in volume vop in which we can define our @P.y of density field.
can you guide me?
thanks.

Hey NimaNolan -

In the pyrosolver, under simulation, there is a setting called Buoyancy Lift. I tried turning it down and helped me keep the flames from rising as fast, which is what we needed.

I'm having another issue that I can't figure out. My container is rendering solid white. I tried searching Google, but nothing helpful came up. Checked to make sure I wasn't viewing just the alpha, and I'm not.

Hello Chris.
Thanks for your response.
but problem that I said in previous is related to flexibility of shader section of houdini's fire!
We really don't need to playing with physical channel of pyrosolver.
i want to have localized heat and temperature field in which user define their own area to acting fields on it.

I think I solved my render issue. Seems to be something with the material. If I create a new one, it renders fine.