require "physics"; require "color"
function pV(x, y) return physics.Vect(x, y) end
function on.resize()
W, H = platform.window:width(), platform.window:height()
X0, Y0, UNIT = math.floor(W/2), math.floor(H/2), math.floor(H/6)
end
TICKING = false
spaceDamping = 0.9
ZERO = pV(0, 0)
LARGE = physics.misc.INFINITY()
DT = 1/(2^6)
GRAVITY = 0
COLOR = {
0xFF7F7F, 0xFF7FBF, 0xFF7FFF, 0xBF7FFF, 0x7F7FFF, 0x7FBFFF, 0x7FFFFF, 0x7FFFBF, 0x7FFF7F, 0xBFFF7F, 0xFFFF7F, 0xFFBF7F,
0xFF6060, 0xFF60AF, 0xFF60FF, 0xAF60FF, 0x6060FF, 0x60AFFF, 0x60FFFF, 0x60FFAF, 0x60FF60, 0xAFFF60, 0xFFFF60, 0xFFAF60,
0x5E5E5E, 0x7E7E7E, 0x9E9E9E, 0xBEBEBE, 0xDEDEDE, 0xFEFEFE,
0x0078BA, 0x0079C2, 0x009944, 0x00A0DE, 0x00A7DB, 0x00ADA9, 0x019A66, 0x522886, 0x6CBB5A, 0x814721, 0x9B7CB6, 0x9CAEB7, 0xA9CC51, 0xB6007A, 0xBB641D, 0xD7C447, 0xE44D93, 0xE5171F, 0xE60012, 0xE85298, 0xEE7B1A, 0xF39700,
}
pBall = class()
function pBall:init(mass, radius, elasticity, friction, color, group)
self.color = color or color.black
local inertia = physics.misc.momentForCircle(mass, 0, radius, ZERO)
self.body = physics.Body(mass, inertia)
self.shape = physics.CircleShape(self.body, radius, ZERO)
:setRestitution(elasticity or 0.8)
:setFriction(friction or 0.8)
if group then
self.shape:setGroup(group)
end
end
function pBall:paint(gc)
local pos = self.body:pos()
local cx, cy = X0 + UNIT * pos:x(), Y0 - UNIT * pos:y()
local radius = UNIT * self.shape:radius()
local diameter = radius + radius
local angle = self.body:angle()
local x0, y0 = cx - radius, cy - radius
gc:setColorRGB(self.color)
gc:fillArc(x0, y0, diameter, diameter, 0, 360)
gc:setColorRGB(color.black)
gc:setPen("thin")
gc:drawArc(x0, y0, diameter, diameter, 0, 360)
gc:drawLine(cx, cy, cx + radius * math.cos(angle), cy - radius * math.sin(angle))
end
pBox = class()
function pBox:init(mass, width, height, elasticity, friction, color, group)
self.color = color or color.black
local inertia = physics.misc.momentForBox(mass, width, height)
self.body = physics.Body(mass, inertia)
local verts = {pV(-width/2, -height/2), pV(-width/2, height/2), pV(width/2, height/2), pV(width/2, -height/2)}
self.shape = physics.PolyShape(self.body, verts, ZERO)
:setRestitution(elasticity or 0.8)
:setFriction(friction or 0.8)
if group then
self.shape:setGroup(group)
end
end
function pBox:paint(gc)
local numVerts = self.shape:numVerts()
local verts = {}
for i = 1, numVerts + 1 do
local j = i; if i > numVerts then j = 1 end
local points = self.shape:points()[j]
table.insert(verts, X0 + UNIT * points:x())
table.insert(verts, Y0 - UNIT * points:y())
end
gc:setColorRGB(self.color)
gc:fillPolygon(verts)
gc:setPen("thin")
gc:setColorRGB(color.black)
gc:drawPolyLine(verts)
end
pStaticSeg = class()
function pStaticSeg:init(x1, y1, x2, y2, elasticity, friction, color, group)
self.color = color or color.black
local avec, bvec = pV(x1, y1), pV(x2, y2)
self.shape = physics.SegmentShape(nil, avec, bvec, 0.05)
:setRestitution(elasticity or 0.8)
:setFriction(friction or 0.8)
if group then
self.shape:setGroup(group)
end
end
function pStaticSeg:paint(gc)
local pos1 = self.shape:a()
local x1, y1 = X0 + UNIT * pos1:x(), Y0 - UNIT * pos1:y()
local pos2 = self.shape:b()
local x2, y2 = X0 + UNIT * pos2:x(), Y0 - UNIT * pos2:y()
gc:setColorRGB(self.color)
gc:setPen("thin")
gc:drawLine(x1, y1, x2, y2)
end
pSpace = class()
function pSpace:init(GRAVITY)
self.space = physics.Space()
:setGravity(pV(0, GRAVITY))
:setDamping(spaceDamping)
self.objects = {}
end
function pSpace:step(DT)
self.space:step(DT)
end
function pSpace:addObj(obj, velx, vely, cx, cy)
obj.body:setVel(pV(velx or 0, vely or 0))
:setPos(pV(cx or W/2, cy or H/2))
self.space:addBody(obj.body)
:addShape(obj.shape)
table.insert(self.objects, obj)
end
function pSpace:addStatic(obj, cx, cy)
if obj.body then obj.body:setPos(pV(cx or W/2, cy or H/2)) end
self.space:addStaticShape(obj.shape)
table.insert(self.objects, obj)
end
function pSpace:paint(gc)
gc:setColorRGB(color.gray)
gc:drawString(string.format("t = %4.1f", timeElapsed), W - 100, 3, "top")
for _, v in ipairs(self.objects) do
v:paint(gc)
end
end
Grid = class()
function Grid:init()
end
function Grid:paint(gc)
gc:setPen("thin")
gc:setColorRGB(0x6495ED)
gc:drawLine(0, Y0, W, Y0)
gc:drawLine(X0, 0, X0, H)
gc:fillPolygon({W, Y0, W - 7, Y0 - 4, W - 3, Y0, W - 7, Y0 + 4, W, Y0})
gc:fillPolygon({X0, 0, X0 - 4, 7, X0, 3, X0 + 4, 7, X0, 0})
gc:drawString("x", W - 10, Y0 - 21)
gc:drawString("y", X0 + 5, -6)
gc:setColorRGB(0xCAE1FF)
local i1 = 1;
while Y0 - UNIT * i1 > 0 do gc:drawLine(0, Y0 - UNIT * i1, W, Y0 - UNIT * i1); i1 = i1 + 1 end
local i2 = 1;
while Y0 + UNIT * i2 < H do gc:drawLine(0, Y0 + UNIT * i2, W, Y0 + UNIT * i2); i2 = i2 + 1 end
local i3 = 1;
while X0 + UNIT * i3 < W do gc:drawLine(X0 + UNIT * i3, 0, X0 + UNIT * i3, H); i3 = i3 + 1 end
local i4 = 1;
while X0 - UNIT * i4 > 0 do gc:drawLine(X0 - UNIT * i4, 0, X0 - UNIT * i4, H); i4 = i4 + 1 end
end
function reset()
timeElapsed = 0
grid = Grid()
space = pSpace(GRAVITY)
ball1 = pBall(30, 0.7, 1, 0.1, COLOR[math.random(#COLOR)],1)
space:addObj(ball1, 0, 0, 0, 0)
ball2 = pBall(0.1, 0.3, 1, 0.1, COLOR[math.random(#COLOR)],2)
space:addObj(ball2, 0, 3, 2.5, 0)
end
function on.construction()
reset()
end
function on.escapeKey()
reset()
end
function on.paint(gc)
grid:paint(gc)
space:paint(gc)
end
function on.timer()
space:step(DT)
timeElapsed = timeElapsed + DT
posA = space.objects[1].body:pos()
posB = space.objects[2].body:pos()
massA = space.objects[1].body:mass()
massB = space.objects[2].body:mass()
vectAB = posB - posA
lengthABsq = vectAB:lengthsq()
normAB = vectAB:normalize()
forceA = normAB:mult(massA * massB/lengthABsq)
forceB = -forceA
space.objects[1].body:setForce(forceA)
space.objects[2].body:setForce(forceB)
platform.window:invalidate()
end
function on.enterKey()
if TICKING == false then timer.start(DT); TICKING = true
elseif TICKING == true then timer.stop(); TICKING = false
end
end
