Transparency

Description:

The Transparency property determines the transparency of all active particles over their individual lifetimes. It works similar to ParticleEmitter/Size in how it affects particles over time. In terms of rendering, it works like the BasePart/Transparency of a part on a scale of 0 to 1, where 0 is completely visible (opaque), and a value of 1 is completely invisible (not rendered at all).

Pictured below are two default ParticleEmitters. The right emitter has a Transparency set to a DataType/NumberSequence that interpolates from 0 to 1.
Two default ParticleEmitters; the right emitter Transparency fades over the lifetime of the particles

A particle’s present transparency is determined by linearly interpolating on this NumberSequence using the particle’s age and the particle’s total lifetime. For example, if a particle spawned 2 seconds ago and has a 4 second lifetime, the transparency will be whatever is 50% of the way through the DataType/NumberSequence. For any DataType/NumberSequenceKeypoint with a nonzero envelop value, a random value in the envelop range is chosen for each keypoint for each particle when it spawns.

Changing this property applies changes to all particles present in the system. This is because the transparency of a particle is determined using its present lifetime and this NumberSequence (the Transparency at the time the particle was emit is not stored on a per-particle basis).

Code Samples

Creating a Particle Emitter from Scratch

This rather lengthy code sample shows how every property of a ParticleEmitter can be set, including DataType/NumberRange, DataType/NumberSequence and DataType/ColorSequence properties. Below is how the ParticleEmitter should after every property is set. Try playing around with the different properties to customize how the effect looks!

The final product

local emitter = Instance.new("ParticleEmitter")
-- Number of particles = Rate * Lifetime
emitter.Rate = 5 -- Particles per second
emitter.Lifetime = NumberRange.new(1,1) -- How long the particles should be alive (min, max)
emitter.Enabled = true 

-- Visual properties
emitter.Texture = "rbxassetid://1266170131" -- A transparent image of a white ring
-- For Color, build a ColorSequence using ColorSequenceKeypoint
local colorKeypoints = {
	-- API: ColorSequenceKeypoint.new(time, color)
	ColorSequenceKeypoint.new( 0, Color3.new(1, 1, 1)),  -- At t=0, White
	ColorSequenceKeypoint.new(.5, Color3.new(1, .5, 0)), -- At t=.5, Orange
	ColorSequenceKeypoint.new( 1, Color3.new(1, 0, 0))   -- At t=1, Red
}
emitter.Color = ColorSequence.new(colorKeypoints)
local numberKeypoints = {
	-- API: NumberSequenceKeypoint.new(time, size, envelop)
	NumberSequenceKeypoint.new( 0, 1);    -- At t=0, fully transparent
	NumberSequenceKeypoint.new(.1, 0);    -- At t=.1, fully opaque
	NumberSequenceKeypoint.new(.5, .25);  -- At t=.5, mostly opaque
	NumberSequenceKeypoint.new( 1, 1);    -- At t=1, fully transparent
}
emitter.Transparency = NumberSequence.new(numberKeypoints)
emitter.LightEmission = 1 -- When particles overlap, multiply their color to be brighter
emitter.LightInfluence = 0 -- Don't be affected by world lighting

-- Speed properties
emitter.EmissionDirection = Enum.NormalId.Front -- Emit forwards
emitter.Speed = NumberRange.new(0, 0) -- Speed of zero
emitter.Drag = 0 -- Apply no drag to particle motion
emitter.VelocitySpread = NumberRange.new(0, 0)
emitter.VelocityInheritance = 0 -- Don't inherit parent velocity
emitter.Acceleration = Vector3.new(0, 0, 0)
emitter.LockedToPart = false -- Don't lock the particles to the parent 
emitter.SpreadAngle = Vector2.new(0,0) -- No spread angle on either axis

-- Simulation properties
local numberKeypoints2 = {
	NumberSequenceKeypoint.new(0, 0);  -- At t=0, size of 0
	NumberSequenceKeypoint.new(1, 10); -- At t=1, size of 10
}
emitter.Size = NumberSequence.new(numberKeypoints2)
emitter.ZOffset = -1 -- Render slightly behind the actual position
emitter.Rotation = NumberRange.new(0, 360) -- Start at random rotation
emitter.RotSpeed = NumberRange.new(0) -- Do not rotate during simulation

-- Create an attachment so particles emit from the exact same spot (concentric rings)
local attachment = Instance.new("Attachment", script.Parent)
attachment.Position = Vector3.new(0, 5, 0) -- Move the attachment upwards a little
emitter.Parent = attachment