Prerequisite Step: This How-To uses the DefaultRibbonMaterial, which is included in the content for the Niagara plugin. However, you can use the M_Balloon material used in the Create a Mesh Particle Effect How-To if you have already completed that tutorial.
Simulating natural phenomena is challenging, especially when using sprite or mesh-based particles to simulate smoke or vapor trails. Ribbon Emitters are an excellent solution for simulating these objects. In the following how-to, you will learn how to set up a Niagara Emitter to emit a continuous ribbon-style particle effect into the world.
Create System and Emitter
Unlike in Cascade, Niagara emitters and systems are independent. The current recommended workflow is to create a system from existing emitters or emitter templates.
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First, create a Niagara System by right-clicking in the Content Browser, and selecting FX > Niagara System. The Niagara Emitter wizard displays.
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Select New system from selected emitters. Then click Next.
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Under Templates, select Simple Sprite Burst.
Using a template will place an emitter instance in your new system, and that emitter instance will have no inheritance.
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Click the Plus sign icon (+) to add the selected emitter to the list of emitters to add to the system. Then click Finish.
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Name the new system RibbonSystem. Double-click to open it in the Niagara Editor.
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The emitter instance in your new system has the default name of SimpleSpriteBurst, but you can rename it. Click the name of the emitter instance in the System Overview, and the field will become editable. Name the emitter FX_Ribbon.
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Change Renderer
The Render group is last in the stack, but you need to change some things so that the effect displays the way it is supposed to. The original template used a Sprite Renderer, but this effect needs a Ribbon Renderer.
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In the System Overview, click Render to open it in the Selection panel.
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To make a ribbon effect, you need a Ribbon Renderer module. But the template has a Sprite Renderer module. Click the Trashcan icon to delete the Sprite Renderer.
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Click the Plus sign icon (+) for Render and select Ribbon Renderer.
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The material you want is not displayed by default. Click the dropdown for Material, and click View Options to open a list of options. Check the boxes for Show Engine Content and Show Plugin Content. Now you will be able to see the material.
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Click the dropdown for Material and select DefaultRibbonMaterial.
If you completed the Create a Mesh Particle Effect how-to, you can select the M_Balloon material instead. This will give you an opaque ribbon, rather than the translucent one created by the DefaultRibbonMaterial.
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Drag the RibbonSystem into your Level.
When you make a particle effect, it is always a good idea to drag your system into a Level. This gives you a chance to see every change and edit in context. Any changes you make to the system automatically propagate to the instance of the system in your Level.
Edit the Emitter Update Group Settings
First, you will edit the modules in the Emitter Update group. These are behaviors that apply to the emitter, and that update each frame.
Even after adding a Ribbon Renderer and editing the settings in the Emitter Update group, you will not see a ribbon appear. This is normal! When you get to the Particle Spawn section of this document, you will start to see the actual ribbon.
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In the System Overview, click the Emitter Update group to open it in the Selection panel.
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Expand the Emitter State module. This module controls time and scalability for this emitter. Because you used the Simple Sprite Burst template, the Life Cycle Mode is set to Self. Normally this is used for complete customization of emitter life cycle logic for this specific emitter, but it is not needed for this effect. Click the dropdown and set the Life Cycle Mode to System. This enables your system to calculate life cycle settings, which usually optimizes performance. By default, the system loops infinitely on a 5 second interval.
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The Spawn Rate module creates a continuous stream of particles while the emitter is active. Add the Spawn Rate module by clicking the Plus sign icon (+) for Emitter Update and selecting Spawning > Spawn Rate.
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Set the Spawn Rate to 100.
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Edit the Particle Spawn Group Settings
Next, you will edit the modules in the Particle Spawn group. These are behaviors that apply to particles when they first spawn.
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In the System Overview, click the Particle Spawn group to open it in the Selection panel.
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Expand the Initialize Particle module. Click the Trashcan icon to delete it. You do not need this module, because there is a different module for initializing ribbons.
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The Initialize Ribbon module performs a similar function to Initialize Particle, in that it collects several parameters into one module. Click the Plus sign icon (+) for Particle Spawn and select Initialize > Initialize Ribbon.
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Under Point Attributes, locate the Lifetime parameter. This parameter determines how long particles will display before they disappear. Set the Lifetime to 5.
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Set the Mass parameter to 10. This will affect how the ribbon spreads outward, as well as how quickly it falls.
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For the Color parameter, set the R (Red) value to 1. Leave the other values at 0. You can change the color later, if you choose.
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Under Ribbon Attributes, set the Ribbon Width to 10.
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To make the ribbon spin in a spiral, you can add a Torus Location module. Location modules affect the shape of the location where the particles spawn. Click the Plus sign icon (+) for Particle Spawn and select Location > Torus Location.
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Under Shape, click the dropdown for Torus Mode and select Ring.
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Set the Large Radius to 50. The Large Radius determines how large the primary ring shape is.
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Under Distribution, click the dropdown for Torus Distribution Mode and select Direct.
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The U Position parameter sets the position on the ring shape. Expand the Emitter Attributes section of the Parameters panel. Drag the Emitter.Age parameter over to the Selection panel; you will see green dotted lines around the fields where you can use that parameter. Drop the Emitter.Age parameter on the U Position value. Your ribbon will look like it is spinning in a static ring, but you will change that in the next step!
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Now you will add some velocity to the ribbon. Click the Plus sign icon (+) for Particle Spawn and select Velocity > Add Velocity From Point.
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Set the Velocity Strength to 50. Now you will see the ribbon start to spiral! This happens because as the position is moving around the Large Radius, the velocity pushes the ribbon outward from the original ring.
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Edit the Particle Update Group Settings
Now you will edit the modules in the Particle Update group. These behaviors apply to an emitter's particles and update each frame.
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In the System Overview, click the Particle Update group to open it in the Selection panel.
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This effect has a single color, so the Scale Color module is not needed. Click the Trashcan icon to delete it.
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Add the Acceleration Force module. This is what makes the spiraling ribbon fall down, simulating gravity. Click the Plus sign icon (+) for Particle Update and select Forces > Acceleration Force.
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Because Niagara adds new modules to the bottom of the group's stack, you will get an error stating "The module has unmet dependencies." That is because the Acceleration Force module was placed after the Solve Forces and Velocity module. Click the Fix Issue button to reposition the module and resolve the error.
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Set the Z value of the Acceleration to -200. A positive Z value would make the ribbon spiral upwards; using a negative value makes it drop downward in a parabolic shape.
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End Result
Congratulations! You have created a Niagara ribbon effect. In the video below, you can see the ribbon effect with the DefaultRibbonMaterial on the left, and the same ribbon effect with the M_Balloon texture on the right.