I recently was working on an effect which needed some mystical “runes”. I was going to draw some when it occured to me this was the sort of thing Houdini does well, why not generate some? It’s the kind of thing that’s been done before in various ways, but it made for a fun little project. Here are some results.
The PopcornFX team honored me recently by including content I’ve created as part of the official 2.10 release. As they work towards a version in which user content can be uploaded and shared freely, the team approached me knowing I had a pack of templates and example projects I was intending to share out to other users. I was flattered and pleased to share this content out via an official release like this.
It’s worth noting that PopcornFX is free to download and use for personal learning, as is this content pack. https://www.popcornfx.com/ The content I’ve contributed can be downloaded directly from the editor and is among the “official” learning content and examples.
By including this content in the 2.10 release they have a demonstration and first test of how new nodes and files can be created by a third party and shared among users.
The content is a collection of 31 “templates” or custom nodes I originally created for myself as I worked with PKFX. The nodes are documented and tested and vary widely in both their usage and usefulness. A few are so helpful I use them in practically everything I do now, while others are very specific in their use cases.
In addition there is a small suite of “example” files showing various effects, each cleanly presented, commented and documented.
I tend to clean and document files for myself as part of my creation process so it didn’t take much effort to prep these files for the public. Hopefully they will spark interest and prove useful as examples of one user’s workflow, in tasks both simple and advanced.
Read more for descriptions of each of the nodes included:
|Random Spherical Vector
|Produces a pure random vector from a unit sphere.
|Random Value In Cone
|Generates a random vector in a conical arc with the center by default oriented in the positive Y axis.
|Test If Points Intersect Plane
|Tests point position to determine if it intersects an infinite plane.
|Plug into acceleration. Updated position is the particle position on current frame. Rest position is the point the spring seeks to reach. Spring constant is a measure of the “tightness” of the spring.
|Wander Around Position
|Randomly moves offset around center point position. Two methods available, with their own strengths and weaknesses. Keep seed values low.
|Applies a unique ID ranging from 0 to 1 for all spawned particles. Only works when there is a total (fixed) number of particles spawned.
|Time Based Rand
|Instead of a unique value per-point this random function delivers a single random value at spawn or per frame.
|Noise function animated over the effect age.
|Produces a boolean and optional values based on a random probability between 0 and 100.
|When used in a “trail” layer this template causes resulting trail to be a spiral around the parent particle’s path.
|Spin on Axis
|Animates an incoming vector (position) to rotate around axis over time.
|Point Visibility By Facing
|Outputs a number 0 or 1 based on whether a point is on the front, back or edge of the sphere of the point normal.
|Flickers colors over the particle’s lifespan.
|Flips between two values based on a random noise.
|Position On Circle
|Outputs a vector which lies on a circle defined by input values.
|Oscillate between two values. User can choose between several waveforms via a dropdown on the node. Speed is in seconds.
|4 Pole Switch
|Choose between 4 inputs via a dropdown list on node.
|3 Pole Switch
|Choose between 3 inputs via a dropdown list on node.
|2 Pole Switch
|Choose between 2 inputs via a dropdown list on node.
|Value by Distance To Camera
|Sets a range of values based on each point’s distance to camera.
|Kill by Camera Distance
|Deletes particles closer or further than a set distance from the camera.
|Identify Single Point
|“Tags” a single point or range of points and returns true when graph evaluates them. Use with billboard “enable” to render a single point.
|Newtons Universal Gravitation Force
|Simple implementation of universal gravitation. Plug into acceleration. Position should be discretized (updated per frame.) Values are arbitrary, not real-world.
|Set Circular Orbital Velocity
|Calculates velocity needed to place point into a circular orbit when using a universal gravitation force. Normal vector is typically the effect.up vector.
|Position On View Axis
|Outputs a position along the axis of the camera into the scene, with distance 0 being the camera position. Useful for defining focal planes etc.
|Defines a color based on the location of a point within a vector field.
|Spatial Basis Rand
|Returns random values based on position in a vector field. Must have a “turbulence” node added to sampler input.
|Distributes all spawned points in a ring or arc. Requires a static (total) number of points.
|Generate Cyber Rings
|Distributes spawned points into a series of circular arcs. Total spawned points must be static, though they can be animated in the layer.
|Distributes spawned points on a line between two input locations. Unlike the debug “draw line” this line is made up of spawned points which can be further animated. Requires a static (total) number of points spawned.
|Useful for “glitch” effects. Offsets positions by a random value at random intervals. Spatial mode requires a turbulence sample.
While making a demo scene for PopcornFX I found a need to make individual particles move on arcs where I could choose a start and end position, height of the arc, and overall placement in 3d space. Depending on how you approach the problem you can easily find yourself slogging through some pretty involved math, at least for the level I’m at. An “arc” can be a parabola, or a section of a circle or so on. A few directions can take you into the woods pretty quickly. I wanted simple.
The simplest approach I’m aware of is to construct a quadratic bezier curve, since it is defined by a start, end and midpoint and can easily be plotted out using a few LERP functions. If you define a start point, end point and midpoint a quadratic bezier curve describes a very intuitive arc, and if you restrict the control point to be perpendicular to the midpoint of the line between your start and end points you get a beautiful parabolic curve in a very intuitive fashion.
Once I had decided on a quadratic bezier, creating a template in PopcornFX was quick, and it wasn’t long before I had a very useful new node in my toolbox. To extend the idea a little further I decided to take a little extra time and make another node for a cubic bezier curve, which is a logical extension of the same approach.
A cubic bezier curve is defined by a start point and end point like before, only this time those two points each have a separate control point to describe a 3d curve. The resulting path can now diverge from a single plane but is still simple enough for the results to be intuitive. In cases where a quick spline is needed in PKFX, this template should allow the artist to describe a simple motion without having to import in a curve or animation. It’s made up of a series of LERP functions and while the idea can be extended further to create fourth or fifth order curves actually wiring up so many LERP’s gets crazy. We’ll stop with our two handy new nodes, the quadratic and cubic beziers.
Here’s what the two look like in PopcornFX. The more complex cubic bezier is the top curve, and the bottom is the quadratic curve, with the midpoint restriction mentioned above:
So from there I had a nice tool to create motion paths of as many separate particles as I needed. To celebrate, I made the following simulation. Yes, we are playing a game of thermonuclear war:
There are a myriad of ways in which the above animation could be approached, but by abstracting out the “arc” motions into templates I am able to finish the project in a way that leaves me with tools for further work in the future. And of course these nodes can not only be re-used, they can be shared out with other artists.
A final benefit is a much more simple graph overall, and best of all we’ve avoided relying on simulation. Sure you could fire each particle like a little mortar and let a physics node calculate the motion up to the point where the particle collides back to earth. But that’s computationally wasteful and worse it cedes control of the results to the parameters you give the simulation.
By abstracting out the arcs the way I did, I am able to easily able to set conditions so that every arc starts from a populated region and ends in a populated region. If you watch the animation you will note no arcs start or end in the ocean. (I admit however that I didn’t go so far as to prevent Canada from nuking the USA and vice versa…)
Similarly I have control over the heights of the arcs, their angle respective to the surface of the world, and the range or distance any point is allowed to travel. Simple procedural approaches can yield visual complexity while retaining control and easing the difficulty of projects!
By the way this image is entirely particles.
The “land” and “city” areas are the result of taking some texture maps of the earth from NASA into Houdini and using them to create PKFX-friendly emitter geometry as .FBX polygonal meshes. This lets me quickly spawn particles exactly where I wanted them as well as define start and end positions for arcs in areas already predefined as valid. No dart-throwing approaches where particles are spawned and then accepted or rejected based on texture maps or the like.
You can’t always predefine information this way but in this case having re-usable meshes defining the landmasses and cities of Earth was another useful set of tools for future projects. Perhaps the next one won’t be quite so apocalyptic…
I haven’t edited an “official” demo reel in a very long time. People know who I am, and hire me for projects based on peer testimonial and having seen past work directly. A reel just hasn’t been needed, since I’m fortunate enough to be a freelancer who gets approached regularly. So when I started teaching students who knew nothing about me I had the challenge of presenting myself to an entirely new audience who were eager to see some work I’ve done in films. I really haven’t had time to edit much, so instead I spent an evening grabbing various shots from films and the like. Stuff I’ve either worked on directly, supervised, or had some hand in.
I have only grabbed a portion of the films I’ve worked on, plus some TV and game stuff, pretty much in the order they were stacked on my desk. The choices are fairly miscellaneous – at the moment I just don’t have time to go through film after film and say “oh yeah, I did that,” then tighten it all down into an edit with music and polish. I know, this breaks all the rules where I’m supposed to present only the very very best, nothing less. But the policy that seems to work best for me is to just be open, good or bad just get it out there and get back to making the next thing. I will never be a charismatic showman or clever self-promoter. I’m a creative geek and frankly I like showing failures, too. It’s part of the process, and that’s what really motivates me.
So all of that said, here’s about 6 minutes of footage and, well, stuff. I basically play it in the background when I introduce myself to students, so it is what it is. Enjoy!
This is a really crude first approximation of a homebrew realtime fluid simulation using vorticles. The general idea is a sparse layer of particles are queried for position and orientation and used as centers of rotation to simulate turbulent fluids. Even this very simple first experiment is very promising.
No noises, fields or turbulence forces are used, the motion is all directly a result of particles interacting with a layer of vorticles, which I reveal in the latter portion of this video.
Simulation is entirely on the CPU and takes 18ms per frame for 21,000 particles. One nice thing about vorticle simulations is the motion does not change with the number of particles, meaning a simulation can be tuned while running very fast and then the simulation turned up for millions of particles to be rendered in After Effects etc. I look forward to seeing how fast this will run when entirely on the GPU.
Apologies for the tiny video… this is just a screen capture.
I created a number of custom emitters for Niagara which I have yet to release to the public. (I wish there was a nice way to package up and share custom modules rather than having to share out entire project files.) These frames are illustrating the use of a fibonacci (or phyllotactic) sphere emitter which is tailor-made for dandelions…
PopcornFX is a great tool for realtime applications in that it brings to developers a ready-to-integrate particle system which can be used to author sophisticated effects in a nodal/visual style akin to Houdini, ICE etc. I find it much more intuitive than Niagara while easily being as powerful, and it’s integration into After Effects brings those users a level of sophistication with particle effects they simply haven’t had access to before. That said, when I push the limits it understandably can’t chew through the millions of particles Houdini can handle.
For example in PKFX this frost-like propagation effect, which is admittedly computationally expensive, tops out in usefulness at about 50,000 particles. The in-editor framerates are still good (relatively speaking) at 220 ms, comfortable enough for cinematography work in After Effects for example. But when you push the number of particles up beyond that times go up exponentially. By 100k particles (for this particular task, which involves getting neighboring particle information) the editor becomes increasingly likely to crash.
But to be fair this kind of propagation effect is waaay beyond what most realtime engines are engineered to handle. Other effects in PopcornFX can get into the realm of millions of particles without too much trouble, which means those After Effects users have a system which lets them perform most particle effects they are likely to need extremely efficiently… and only need to go to a package like Houdini for the really intensive stuff.
And at the moment these computations are only on the CPU as PKFX is still implementing its GPU support. There is a lot of improvement on the near horizon for these kinds of intensive effects… we may see sph fluids and the like running realtime soon enough.
(It’s also worth mentioning that there is a LOT of room to optimize the effect as built, both with regular settings and as one of the PopcornFX devs points out massive increases in efficiency should be possible by only performing spatial queries on the particles changing values and depositing stable values into a static layer.)
It’s significant that those integrating PopcornFX into realtime tools get a system sophisticated enough that a comparison with Houdini is even possible.
In all, I’m pretty impressed with PKFX and as an effects guy would welcome jobs where it’s integrated into custom pipelines dealing with realtime media even over Niagara and certainly over Unity’s particle system. It is elegant to use without sacrificing power, and it’s universal nature means one day artists might be able to share and use particle assets across multiple engines and custom pipelines.
I’ve been using PopcornFX a lot lately and have been using it as a playground to explore some simple physics simulation. For example Hooke’s law and compressible springs:
And it was pretty fun exploring Newton’s law of universal gravitation with a classic “orbit” simulation:
But then it occurred to me… PopcornFX is pretty efficient, why not scale up my basic simulation to handle not only a few orbiting bodies, but hundreds of thousands? While not correct to the universe we live in the result should look a bit like elliptical galaxies, right?
Let’s try it.
Ok then, here’s a screenshot of a sim of around 900k particles, running 30-50ms per frame. Too slow for game work but pretty fast for cinematics, and PKFX is integrated into After Effects so I really should try rendering out a movie.
In motion the effect is mesmerizing, with “galaxies” merging, splitting, devouring each other and for some reason periodically seeming to explode into rope-like strands. Nowhere near physically correct of course, but evocative of space imagery and very beautiful.
Why no spiral galaxies? In the real world a lot more is going on, with gasses compressing and angular momentum preserved. This little simulation doesn’t account for more than the most basic, crude motion so, alas, the “galaxies” which form are elliptical only and rarely stable for very long.
I need to revamp the website gallery… in the meantime here is a collection of miscellaneous still images, mostly just personal experiments and the like, some better than others. :P