Codea Codify object sort and alpha transparency demo

--alphas and sort comp
--seeing though things and sorting a table of objects

iparameter("leafThickness",0,255,128)

function setup()
    forest = {} --create a table called forest
    for i = 1,10 do
        --create 10 plants in the forest
        --this calls the function Plant:init(x,y)
        --the x is adjusted to 80% of screen width with 10% added
        --the trees show up in the middle 20% to 80%
        --this prevents the green part of the plant from going off the screen
        --the y is adjusted so the the base of the tree will start in the lower 80%
        --this prevents a plant being drawn off the top of the screen
        forest[i] = Plant((math.random() * WIDTH * .8)+(WIDTH*.1),math.random() * HEIGHT * .8)
    end
    --print before sort
    for i,v in ipairs(forest) do
        print(forest[i].rooty,i,v)
    end
    --sort the trees in reverse y (height) order
    --this prevents the trunk of one plant being drawn over the green part of another
    --reverse the "a.rooty > b.rooty" and respawn to see overlapping trunks
    --rooty is the y value (height) of a plant
    table.sort(forest, function(a,b) return a.rooty > b.rooty end)
    --print after sort
    for i,v in ipairs(forest) do
        print(forest[i].rooty,i,v)
    end
end

function draw()
    background(0, 0, 0, 255)
    --simple loop to draw all plants
    --this calls plant:draw for every plant in the forest table
    for i,v in ipairs(forest) do
        forest[i]:draw()
    end
end

Plant = class()
--usally a seperate tab called plant

function Plant:init(x,y)
    --store the given x and y as rootx and rooty
    self.rootx = x
    self.rooty = y
    --create a table of berry within this plant object
    self.berry = {}
    for i = 1, 100 do
        --create 100 berries
        --the numbers are just to keep the berries within the green part of the plan
        --the numbers are swags, using real math would have given a non-rectanle placement
        x = (math.random() * 74) + self.rootx - 41
        y = (math.random() * 30) + self.rooty + 39
        --record the position of each berry x and y as x and y
        self.berry[i]={x=x,y=y}
    end
end

function Plant:draw()
    --start with the bottom of the plant
    x = self.rootx
    y = self.rooty
    --draw trunk -- basically a brown Y
    stroke(156, 109, 25, 255)
    lineCapMode(PROJECT)
    strokeWidth(20)
    line(x,y,x,y+32)
    strokeWidth(10)
    line(x,y+32,x+16,y+48)
    line(x,y+32,x-16,y+48)
    --draw leaves, a green oval
    strokeWidth(5)
    --the 128 is what makes the leaves semi-see though
    fill(57, 255, 0, leafThickness)
    noStroke()
    ellipseMode(CORNERS)
    ellipse(x-50,y+30,x+50,y+80)
    fill(255, 0, 221, 255)
    --draw all the berries
    for i,v in ipairs(self.berry) do
        ellipse(self.berry[i].x,self.berry[i].y,self.berry[i].x+5,self.berry[i].y+5)
    end
end