Thursday, 18 September 2025

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UE5 Niagara Notes

 The Basics

    Niagara has four core components: 
  • Systems
    • a system is a container that holds your effect. You can apply settings on the system that affect everything inside it. 
    • Has a timeline panel in the system editor that shows emitters and can also manage it. 
  • Emitters
    • where particles are generated
    • controls how particles are born, what happens when they age, and how they look and behave
    • organized in a stack, inside of which is several groups, inside which you can put modules to do tasks
                                    
    • These groups are:
      • Emitter Spawn: 
        • what happens when an emitter is first created
        • defines initial setups
      • Emitter Update: 
        • defines modules that occur every frame on the CPU
        • used to define spawning of particles when you want them to continue spawning on every frame
      • Particle Spawn: 
        • Called once per particle when it is first born
        • defines initialization of the particles, such as birth location, color, size, etc
      • Particle Update:
        • called per particle on each frame
        • use to define anything that needs to change frame-by frame as the particles age (ex: if particles color/size change over time, or if particles are affected by some type of force). 
      • Event Handler:
        • create generate events in one or more emitters
        • then create Listening events in other emitters to trigger a behavior in a reaction to a generated event
      • Render:
        • define the display of particles
        • use mesh renderer if you want to define a 3D model as the basis of your particles
        • use a sprite renderer if you want particles as 2D sprites
        • many other renderers to choose from
    • These are color coded so that anything green is related to the emitter, and the red is anything related to the particles
  • Modules
    • building blocks of effects
    • add modules to groups to make a stack
    • processed sequentially from top to bottom

    • Think of it as a container for doing some math, you pass in some data, then write that data out at the end of the module
Data flow of a module

    • Modules are built using HLSL or using the node editor. 
HLSL logic flow


    • double click any module to look at the graph inside
    • scripts start with getting an input and at the end writing that output back out so modules further down the stack can use it
  • Parameters    
    • four types of parameters:
      • Primitive: numeric data of varying precision and channel widths
      • Enum: fixed set of named values
      • Struct: combined set of primitive and enum types
      • Data Interfaces: defines functions that provide data from external data sources
    • add custom parameter module and then you can add new parameters to it.

Niagara Asset Browser Window


  1. Content Area
  2. Categories
  3. ToolBar (with the filter and Search bar)
  4. Details
    You can add your own tags to these assets inside the content browser. These tags will show up in the categories tab. Explained more in detail on this page.

The VFX Workflow

  1. Create a system to hold and adjust the properties of your emitters
  2. Create emitters inside your system.
  3. Create Modules inside your emitters
    1. each module, emitter, system you create uses resources. To conserve resources, try to see if you can accomplish what you want with the things you've already created.

Resources


Notes on Specific parts of the Niagara System

Particle Spawn

Initialize Particle

Lifetime mode

    You can set this to Random or Direct Set. With random you can set a minimum and maxium range to determine the lifetime of each particle. So some particles will die at the minimum value and some will die at the maximum value. With Direct set you can set a static value that all particles will die at. You can also select other sources, such as a Random Range Float value for Direct set as well (why you would do this I'm not sure since this makes it act like Random, but you could perhaps use other sources?) 

Position Mode

    Determines where your emitter spawns in the scene. By default it is at Simulation Position, so wherever your Niagara system actor is in the scene. The emitter spawns at that point. You can also set the offset as well.
    If you choose direct set, then the particle system will ignore where it Niagara system actor is in the scene and spawn at the specified coordinate. 

Particle Update

    Here you can apply forces during the particles habit.

Drag

    Particles slow down as they progress through their lifetime. 

Curl Noise Force

    Applies random noise force to the particles. Lower Frequency means the bigger the overall pattern the particles will fall to. Higher frequency will cause add smaller random forces to the particles. 
    Keep the Noise Quality/cost low because usually you won't see much of a difference between the low and high quality. 

Point Attraction Force

    Used to attract the particles to one specific point. If you have a low drag amount, the particles might bounce past the point and then get sucked back into it, making it look like a wobble ball of particles. 

Vortex Force

    Causes the particles to move in a spiral shape. 

Point Force

    Opposite from the Point Attraction Force module, this pushes particles away from a point. Mess with the Force Falloff Distance parameter combined with a point attraction force module to have the particles coalesce around an orb after the initial burst.

Wind Force

    You can choose the direction the wind is facing and have the particles drift in that direction. 
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Houdini Workshop - Weeks 1-4

    These are all of my notes from the first two Houdini Workshop days. I will continue uploading my notes as the workshop continues. These weeks continued to iterate over the island project.

    One of the things discussed in the workshop is the idea of levels of noise. If you want something to be realistic in VFX, you need 3 levels of noise to make it believable. Big, medium, and then small, with the amplitude of the noise getting smaller as you go through each level.

    Voxels were also discussed, you can think of them as 3D Pixels.

Starting out

    First  we need a curve node to draw the outline of the island. The curve node is a similar tool to Photoshop's pen tool. Once the curve is complete, we need to change the normals, as they are currently facing down away from us. Make a reverse node to show the Normals right side up. If we don't do this step it wouldn't render correctly. Finally, add a polyExtrude node to give it some depth. 



Making Volcanos

    We're starting to make a rough outline of our island. Now we want to add in mountains and volcanos using cylinders. Create a cylinder node. and adjust the top radius so the bottom radius is larger. Then use a transform node to adjust the position and size. Duplicate this with how many volcanos/mountains you want. 

Change the first input box for radius to change the top radius



    Once you've finished making enough mountains, you'll need to combine them all, including your island shape into a Merge node. 

Should look like this for now

Heightfield Node

  
    Now drop in a heightfield node, make it large like 4,000 by 4,000. Heightfields are useful in making realistic terrains. Using a heightfield projection node we can use the geometry we just made to 'shrink wrap the heightfield's volume around it. The heightfield uses voxels instead of polygons, so it'll appear smoother.
    You'll want to have the heightfield in the first input slot, and the merge node in the second input. 
    We have the heightfield set up, and we can use different nodes Houdini already has dedicated to manipulate heightfields to get a realistic looking Terrain. However, we first want to create a mask so the noise doesn't affect the water around the island. 

Heightfield Mask by Geometry

    You need a Heightfield mask by geometry node. First connect the heightfield project node to the first input, then connect the merge node you have with all the volcanos and poly extrude. You shouldn't have to change anything in the parameters. In the viewport you should see your island show up red. Anything in red is what will be affected. Everything outside the red will be masked out. 

    We'll want to adjust the mask so it fades off as it goes into the water. Add a mask shrink node and change the radius to around 50. Then add a heightfield mask blur node and change the radius to around 100. 

    The mask is now finished and we can now move onto adding noise to the terrain. 

Adding Noise

    We can consider the base island shape and the cylinders to be our first level of noise. They're for blocking out the overall shape. Now we'll start on our second level of noise with a Height Field Noise Node. 

        Insert the heightfield project node into the first input of the heightfield noise node, with the second input coming from the mask we just made. Change the parameters to: 
  • Noise Type: Worley Cellular F2-F1
  • Amplitude: 200
  • Element size: 810 (this is the scale of the noise)
  • Turn off "center noise: (noise is actually 4 dimensions of numbers, center noise means the noise starts in the center of the scene, aka the origin) 


Additional Resources

https://www.youtube.com/watch?v=Oe0_C14lYgU 
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