particles

particles.lua

-- A converted javascript (by Keith Peters) adapted for Codea by Bri_G
-- ref. http://www.bit-101.com/blog/?p=3148
-- excellent description given 

-- Use this function to perform your initial setup
function setup()
    -- initialisations of system and variables used
    displayMode(FULLSCREEN)
    points = {x={}, y={}, z={}, vx={}, vy={}, size={}, colr={}}
    numPoints = 50
    bounce = -1
    
    wide = WIDTH
    height = HEIGHT
    
    for i = 1, numPoints do
        points.x[i] = math.random(wide)
        points.y[i] = math.random(height)
        points.vx[i] = math.random(6,10) - 5
        points.vy[i] = math.random(6,10) - 5
        points.size[i] = math.random(10,30)
        points.colr[i] = color(math.random(50,255),math.random(50,255), math.random(50,255),255)
    end  
end

-- This function gets called once every frame
function draw()
    -- This sets a dark background color 
    background(0, 0, 0, 255)
    -- This sets the line thickness
    strokeWidth(1)
    -- Do your drawing here
    for i = 1,numPoints do
        pts = points.size[i]
        fill(points.colr[i])
        ellipse(points.x[i], points.y[i], pts, pts)
    end
    update()
end
 
function update()
    for i = 1, numPoints do
        points.x[i] = points.x[i] + points.vx[i]
        points.y[i] = points.y[i] + points.vy[i]
        if points.x[i] > wide then
            points.x[i] = wide
            points.vx[i] = points.vx[i]*bounce
        elseif points.x[i] < 0 then
            points.x[i] = 0
            points.vx[i] = points.vx[i]*bounce
        end
        if points.y[i] > height then
            points.y[i] = height
            points.vy[i] = points.vy[i]*bounce
        elseif points.y[i] < 0 then
            points.y[i] = 0
            points.vy[i] = points.vy[i]*bounce
        end
    end
end