This week actually went surprisingly well all things considered, I had very minimal Houdini crashes, maybe only 1 or 2! Since I finally have started to move past the rough learning phase of familiarizing myself with Houdini volumes and pyro simulations, things have started going at least a bit more smoothly as I’ve worked on trying to refine my sims and make them look closer to my reference.

My first task for this week was doing some research based on Nelson’s recommendations for how to make my fire look and act more realistic. He told me that I should think about what kind of fire in real life I believe is closest to my desired effect, and look up the temperature of how hot that kind of fire burns to apply to my pyro simulation. I ended up finding that a kerosene fire/explosion looks the most similar to the quick burst of bright flames and minimal smoke that I wanted, and though I found a lot of different information, I gathered that the average temperature of kerosene flames is about 1085 degrees in Kelvin.

I applied this information to the reference temperature field in my pyro solver node and also changed the ambient temperature of the room to be a little bit cooler. These adjustments made a subtle difference in the way my flames acted and how quickly they cooled down, but one that I think helps to make all the difference when it comes to having detailed and realistic flames.

Also regarding the initial burst, Nelson gave me some more advice at our last critique on new and different ways to try creating the source shape and velocity for the burst. The new method I decided to try was essentially creating a new node branch off of my main source sphere, matching the velocity of the sphere to its normals, and creating an attribute noise to control the shape of the velocity and essentially sculpt it into my desired shape by adjusting the noise pattern.

I will say, adjusting the noise pattern proved to be quite tedious and required a lot of convoluted grouping to get the noise to apply on the sphere the way I wanted it to, but I definitely wasn’t mad at the end result. This method helped to get rid of the stringy feeling I was getting from my original initial burst, since the flames were conforming a bit too much to the curves I was using as their source geometry. Instead, this new method made the explosion feel a lot more organic and realistic, starting out as a sphere of fuel that gets pushed out by its velocity and dissipates.

In addition to continuing to work on the initial burst, I also finally started on one of the other parts of this shot this week. I decided to tackle the flame shell next since I had a pretty good idea of how to create the source particle simulation for the flames. If you followed my journey last semester in the creation of the scarlet witch magic effect, you might remember the particle sim effect I discovered that allowed me to make the particles orbit around a central sphere geometry that I ended up using to help shape my core. Immediately when I saw this part of the flames, I knew that the orbiting particle simulation would be perfect for achieving the shape of the fire-wreathed orb in my shot from The Nevers.

So, that’s exactly what I ended up doing. I made the particle simulation utilizing the gravitational pull and orbit techniques I explored during my scarlet witch project (check out Era VFX on youtube to learn more about that method!), adjusting the wind on the pop net to get the desired circular and slightly stringy pattern. I also ended up using the clumping attribute blur node I created for my scarlet witch magic as well on the pop sim, since it helped me get rid of the stray particles and condense the shape into something more uniform.

After that it was pretty straightforward, I plugged my pop net into the necessary nodes to reach the pyro solver and came out with something that actually looks decent! After playing around in the pyro solver for a bit, I was able to start to get the motion similar to my reference, but the one thing that evaded me was how to get it to appear and grow like it does in the shot from The Nevers. The best I could do for this week was keyframe the temperature and burn attributes to make a kind of fading in effect, but I want to be able to make it slowly grow in size to come into frame instead.

So this is my rough work in progress shot for the week that I ended up with! As I’m sure you’ll notice, I also reset the pyro shader gradient to the default, since I was advised (understandably so) not to mess with that until my flame simulation itself is more finalized.

Can you tell that my blog posts have gradually started to get more hopeful and optimistic again? This journey has certainly been a rough one so far, but I finally feel like I’m starting to get the hang of things when it comes to dealing with pyro in Houdini. I still certainly have a long way to go, but it’s nice to not feel completely lost and frustrated finally. But what can I say, Houdini never fails to keep me on my toes when learning new VFX!