Particle effect example - fireworks

This example shows a fireworks effect made with particles.

This effect consists of two particle effects: trail and bang. In this example there are three different colors, which could be easily changed in particle emitters settings.

The main script fireworks.script spawns the fireworks trail particlefx on startup or when any key is pressed or the mouse button is clicked. It also has a timer that spawns the particlefx in a loop with a 3 second delay.

To start effect:

add factories for splat and trail particles;
call “start_fireworks” method with parameters (time, start point, speed vector).

Images for particles are taken from Kenney Particle Pack.

Scripts

fireworks.script

local colors = {"red", "green", "blue"} -- list of existing fireworks colors
local instances = {} -- list of active fireworks instances

local _tension = 0.9 -- emulation of air tension. More value leads to faster deceleration
local _gravity = 980 -- gravity, measuring in mm/sq.s.

local function start_fireworks(trail_id, bang_id, start_pos, speed, time, gravity, tension)
	go.set_position(start_pos, trail_id)
	particlefx.play(trail_id)
	local m = {
		update = function(self, dt)
			if self.time > 0 then
				local prev_pos = vmath.vector3(self.start_pos)
				self.start_pos.x = self.start_pos.x + self.speed.x*dt
				self.start_pos.y = self.start_pos.y + self.speed.y*dt

				local triangle = vmath.vector3(prev_pos.x - start_pos.x, prev_pos.y - start_pos.y, 0)
				local angle = math.atan2(triangle.y, triangle.x)
				self.speed.x = self.speed.x - self.speed.x * self.tension*dt
				self.speed.y = self.speed.y - self.speed.y * self.tension*dt - self.gravity*dt

				go.set_position(self.start_pos, self.trail)
				go.set_rotation(vmath.quat_rotation_z(angle+math.pi/2), self.trail)
				if self.time > 0 then
					go.set_scale(self.time, self.trail)
				end

			elseif self.time <= 0 and not self.is_stopped then
				self.is_stopped = true
				particlefx.stop(self.trail, { clear = true })
				go.set_position(self.start_pos, self.bang)
				particlefx.play(self.bang)
			elseif self.time <= -1.5 and self.bang  then
				go.delete(self.bang)
				self.bang = nil
			end
			self.time = self.time - dt
		end,
		start_pos = start_pos,
		time = time,
		speed = speed,
		gravity = gravity or _gravity,
		tension = tension or _tension,
		trail = trail_id,
		bang = bang_id
	}

	return m
end

local function single_shot()
	if #instances > 5 then
		return
	end
	local color = colors[math.random(1, #colors)]
	local splat = factory.create("#"..color.."_splat_factory")
	local trail = factory.create("#"..color.."_trail_factory")

	local strength = 1000+math.random()*600 		-- scalar value of speed
	local angle = (-0.2+math.random()*0.4)*math.pi	-- angle beetween central vertical line and trail
	
	local pos = vmath.vector3(360-math.sin(angle)*350, 0, 0)
	local speed = vmath.vector3(strength*math.sin(angle), strength*math.cos(angle), 0)
	table.insert(instances, 
		start_fireworks(trail, splat, 
			pos, speed, 
			1.2+math.random()*0.5
		)
	)
end

function init(self)
	single_shot()

	timer.delay(3, true, single_shot) 

	msg.post(".", "acquire_input_focus")
end

function update(self, dt)
	for i, val in ipairs(instances) do
		if not val.bang then
			table.remove(instances, i)
		else
			val:update(dt)
		end
	end
end

function on_input(self, action_id, action)
	if action_id == hash("mouse_button_left") and action.pressed then
		single_shot()
	end
end