Collision Circle/Square or Rectangle with Pico8


1- Collision circle/square with sine and cosine just for fun!
 

 

Sometimes I do useless stuff just for fun and to get my brain fired up, when simpler solutions exist!!! If you had to choose only one solution, the second one is the most reasonable ;-) 

 

#pixcode 1: Detect the corners of a square
 

 #pixcode 2: There is a collision, but D > 0, so the collision is not detected. We need to check the vertical and horizontal alignment.


 function _init()
--circle center
x1=90
y1=60

--square center
x2=60
y2=80

d=10 --square side/2
r=10 --radius

end

function _update()

--controls
if (btn(0)) x1-=1
if (btn(1)) x1+=1
if (btn(2)) y1-=1
if (btn(3)) y1+=1

--calculate oc
a=abs(x1-x2)
b=abs(y1-y2)
oc=sqrt(a^2+b^2)

--calculate sine and cosine
cosa=b/oc
sina=a/oc

--calculate di. The value 0.7071 is only for a square
if cosa <= 0.7071 then
    di=d/sina
else di=d/cosa
end

--check collision with a corner or middle edge
if (oc<=(r+di)) then
    corner=1
else corner=0
end

--check the collision with edges
if a<=d and b<=(r+d) then
    touchh=1
else touchh=0
end

if b<=d and a<=(r+d) then
    touchv=1
else touchv=0
end

--calculate Deltad (not necessary)
deltad=oc-(r+di)

end--end update


function _draw()
cls()

--draw points
pset(x1,y1,8) --circle center
pset(x2,y2,10) --square center

--circle
circ(x1,y1,r,8)
--square
rect((x2-d),(y2-d),(x2+d),(y2+d),10)


--collision detection
if  corner==1 or (touchh==1 or touchv==1) then
    rectfill((x2-d),(y2-d),(x2+d),(y2+d),8)
end

--line circle center to square center
line(x1,y1,x2,y2,14)


end

 

 

2- Collision circle/rectangle or square (easy!)

#PIxcode 3: Check collison with corners of a rectangle or a square

This method is the easiest ->


pico-8 cartridge // http://www.pico-8.com
version 30
__lua__


function _init()
--circle center and radius
x1=90
y1=60
r=10
--rectangle center, width and height. For a square w=h
x2=60
y2=80
w=40
h=20

end--

function _update()
--controls
if (btn(0)) x1-=1
if (btn(1)) x1+=1
if (btn(2)) y1-=1
if (btn(3)) y1+=1

--calculate dh,dv,
dh=abs(x1-x2)
dv=abs(y1-y2)
distx=(dh-(w/2)) --dx
disty=(dv-(h/2)) --dy
distr=distx^2+disty^2 --d

--check collision with corners
if distr<=r^2 then
    collision=1
else collision=0
end

--check the collision with horizontal edges
if dh<=(w/2) and dv<=(r+(h/2)) then
    touchh=1
else touchh=0
end
--check the collision with vertical edges
if dv<=(h/2) and dh<=(r+(w/2)) then
    touchv=1
else touchv=0
end

end



function _draw()
cls()
--draw points
pset(x1,y1,8) --circle center
pset(x2,y2,10) --square center

--circle
circ(x1,y1,r,8)
--square
rect((x2-(w/2)),(y2-(h/2)),(x2+(w/2)),(y2+(h/2)),10)


--collision detection
if  collision==1 or (touchh==1 or touchv==1) then
    rectfill((x2-(w/2)),(y2-(h/2)),(x2+(w/2)),(y2+(h/2)),8)
end

--line circle center to square center
line(x1,y1,x2,y2,14)

end



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