22. Raytracing

22. Raytracing

--# Main
-- Main

function setup()
    t=Track1()
end

function draw()
    t:draw()
end

function touched(touch)
    t:touched(touch)
end
--# Track1
Track1 = class()

function Track1:init(x)
    self.car={x=350,y=100}
    self.FOV=75 --degrees each side
    self.slice=5 --degrees per view
end

function Track1:draw()
    background(128)
    spriteMode(CORNER)
    --create new shapes every second or sl
    if counter==nil then counter=0 end
    counter = counter + 1
    if counter%60==1 then --every 60 redraws, or about one second
        screen=image(WIDTH,HEIGHT) --draw on an image the same size as the screen
        setContext(screen)
        fill(0,0,255,100)   
        for i=1,3 do   
            rect(self.car.x+math.random(-200,200),self.car.y+math.random(100,500),
                    math.random(10,100),math.random(10,100))
            ellipse(self.car.x+math.random(-200,200),self.car.y+math.random(100,500),math.random(10,100))
        end
        setContext()
        views=self:GetRays(screen)
    end
    sprite(screen,0,0)
    fill(255,0,0)
    ellipse(self.car.x,self.car.y,20)
    stroke(0,100,200,200)
    strokeWidth(1)
    if views~=nil then
        for i,v in ipairs(views) do
            line(self.car.x,self.car.y,v.x,v.y)
        end
    end
end

function Track1:GetRays(s)
    local rays={} --to store results
    local f=math.pi/180 --to convert degrees to radians
    for i=-self.FOV,self.FOV,self.slice do
        local d,dy,dy=0,0,0 --distance to object, and x,y position of object
        for u=1,1000 do --put a limit ont he looping
            local xx=self.car.x+u*math.sin(i*f) --step forward
            local yy=self.car.y+u*math.cos(i*f)
            --if in bounds, and pixel non blank, we've hit something
            if xx>1 and xx<=WIDTH and yy>1 and yy<=HEIGHT then
                local r,g,b,a=s:get(xx,yy)
                if b~=0 then d=u dx=xx dy=yy break end
            else break end
        end
        --store angle, distance and x,y position of object
        if d>0 then table.insert(rays,{angle=i,dist=d,x=dx,y=dy}) end
    end
    return rays
end

function Track1:touched(touch)
    --dummy for now
end