nodes

Contribution to PopcornFX 2.10 Now Released

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:

New nodes

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.
Spring Force
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.
Normalized ID
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.
Animated Noise
Noise function animated over the effect age.
Linear Probability
Produces a boolean and optional values based on a random probability between 0 and 100.
Spiral Trails
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.
Sparkle Color
Flickers colors over the particle’s lifespan.
Flicker Value
Flips between two values based on a random noise.
Position On Circle
Outputs a vector which lies on a circle defined by input values.
Oscillator
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. 
Color Turbulence
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.
Generate Ring
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.
Generate Line
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. 
Random Static
Useful for “glitch” effects. Offsets positions by a random value at random intervals. Spatial mode requires a turbulence sample.

 

Creating Bezier Curve Nodes in PopcornFX

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…