Week One
- gracieszymanski04
- Apr 28
- 5 min read
Updated: May 12
Posts arranged newest to oldest.
This week's most recent progress:
To do:
Polish body particle sim
Create Smoke Sim
Polish/create sparkle sims
Figure out what to do with the eyes
Environment Sim?
Polish lookdev with compositing/ambient occlusion layer
5/11/25
After creating my body outline particle system for the cat yesterday, today, I started on the lookdev portion of this sim. I adjusted any noise patterns I used to my liking and then followed the tutorial I referenced earlier to create the color. I used an attribute vop node to create a colorful effect for the cat. Inside this vop, I used a flow noise and the age and rest attributes to create a flowing color effect. This also causes colors to slowly appear one by one as the particle system flows. There is also a ramp node in here, allowing for me to control which colors are visible and how much of each.

When deciding what colors to use, I also started developing my idea further. I considered doing the classic icy blue colors of the Harry Potter patronus creates but I wanted to stray from that a bit. I found these reference images of magical cats when looking at photos on Pinterest. I want to use more of this rainbow, warm color pallet for my magical cat. I also want to create these sparkles in my project as well that I often see in these references:
Here's how the color ramp currently looks like, based on these references:

Here's the updated particle swirls with these colors:
And here's a test render for this pass using Karma on the SCAD render farm:
I feel like the color change is going a bit fast right now so I want to slow that down for future passes. I also plan on using an ambient occlusion compositing pass to create some shadows in these glowing particles. I think this will help with distinguishing the cat's features more.
Moving on from this simulation, I started work on the sparkle simulations that will be added on top of this one.
For the sparkles, I want to have three different popnets:
A floaty sparkle sim
A floaty sparkle sim with an actual star model copied to points
Sticky sparkles with a star model
For the star model I will be copying to points, I found this free model on turbo squid I will be using:
I had time today to just start on the first sim, the floaty particles. I scattered points along my geometry, and then used just a pop wind and pop collision detect to create some floaty sparkles.
Floaty sparkle sim test:
With the work I've done today, I also began thinking about how I want to tackle the environment that the magical cat will be in. If I have time for another simple sim, I had two ideas. The first being to do a pixie dust inspired swirly trail that moves around the cat and in the background. The other idea would be to do some random floating particles that hover over the ground, similar to how particles often float in enchanted forest settings.
Here's some reference for these ideas from Pinterest.com :
5/10/25
I began work on the simulations for this project today. For the simulation itself, I will be using multiple layers of particle simulations, as well as a smoke pyro layer on the simulation.
Current plan for all the layers I need:
Body outline glowing layer
Smoke pyro that flows of the body and upwards
Sparkle particles that float up off the body
Possibly another layer of particles floating up off the cat and swirling
I found this tutorial online with an in depth explanation of how to make a Harry Potter patronus in Houdini. I wanted to start with this tutorial to begin, but I want my magical cat to be more unique to me rather than an exact Harry Potter replica, so I will be using this video more to help with one of my particle layers, rather than a fill replication.
I used this creators method to create swirly patterns of particles on my cat model:
There are two layers of noise that get used to create this effect. First, there is noise created onto the model using an attribute vop node. Inside the attribute vop, a vein noise node and another standard noise node are multiplies together to create this noise effect on the body. The white areas of the noise then as the areas in which the particles spawn from the mesh in the popnet.
The other type of noise used is noise within a volume, created using a volume vop node. Inside the volume vop, there is a curl noise node that is animated to create a volume with curling movement. Here is that volume visualized with a velocity trail node.

This curly noise is used in the popnet so that the particles follow the velocity of the curls. These combined in the popnet allow for the swirly particle effect created on the cat.
5/8/25
Today, I started work on the project by narrowing down models and picking one. I wasn't quite sure if I wanted to magical cat to be running or idle so I found this model that was rigged and animated with a few different options for movement. Since I will just be using more of the outlines of the cat without the textures or details, I was fine the rather cartoonish features as they wouldn't show up.
I ended up preferring an idle movement for the magical cat. Here is the idle movement I chose for the cat and imported to Houdini:
My next step in working with this mode was making sure the geometry was optimized. To do so, I used subdivide, remesh, and smooth nodes to ensure a model that would work well with simulations.
5/4/25
Concept ideation:
For my project, I knew I wanted to do something particles and also lean more toward particles. I remember seeing a project on a friend's demo reel that was a glowing/magical horse appearing from a picture frame and running. I took a lot of inspiration from this piece and thought it reminded me of a patronus creature from the Harry Potter franchise. Therefore, I want to create my own version of this project, heavily referencing the Harry Potter movies, and create a magical cat creature.
References:
Min's Work
Harry Potter:
Possible models:

Really expensive but a great model option:

Project brief from deborahfowler.com:
Goals:
To explore techniques discussed during the quarter and produce a well-rounded portfolio piece.
Requirements:
The specifications and criteria for this project are purposefully as broad as possible to allow you to explore Houdini in the manner you are most interested in.
shot will be 5–10 seconds. (longer shots should be pre-approved)
resolution will be 1920 by 1080 pixels (or maximum size reasonable to produce if
rendering toward end of quarter)
integration with a background plate is optional, but encouraged only if you have those
skills
Your project must include one of the following: pyro, fluid or crowds
You will be producing a visual technical breakdown for the shot
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