Top down car game

jdbc · April 2015

I was developing a prototype of a top down car racing game and now I need to integrate objects collisions (without box2d because it is too complex). I was using TNT Collision engine and oBoxToObox function to check collision between car and objects due to the fact the car rotates, but it does not work.

Do you have any lua code to check collision between rectangle rotated?

You can download the source code to check it from here:
https://github.com/jdbcdev/topdown_racing

hgvyas123 · April 2015

try this code

local rect1 = Bitmap.new(Texture.new("images/yellow.png"))
rect1.width = rect1:getWidth()
rect1.height = rect1:getHeight()
rect1:setPosition(100, 100)
rect1:setRotation(45)
stage:addChild(rect1)
 
local rect2 = Bitmap.new(Texture.new("images/blue_car.png"))
rect2.width = rect2:getWidth()
rect2.height = rect2:getHeight()
rect2:setPosition(200, 200)
stage:addChild(rect2)
 
function onMouseDown(self, event)
	if self:hitTestPoint(event.x, event.y) then
		self.isFocus = true
 
		self.x0 = event.x
		self.y0 = event.y
 
		event:stopPropagation()
	end
end
 
function onMouseMove(self, event)
	if self.isFocus then
		local dx = event.x - self.x0
		local dy = event.y - self.y0
 
		self:setX(self:getX() + dx)
		self:setY(self:getY() + dy)
 
		self.x0 = event.x
		self.y0 = event.y
 
		event:stopPropagation()
	end
end
 
function onMouseUp(self, event)
	if self.isFocus then
		self.isFocus = false
		event:stopPropagation()
	end
end
 
rect1:addEventListener(Event.MOUSE_DOWN, onMouseDown, rect1)
rect1:addEventListener(Event.MOUSE_MOVE, onMouseMove, rect1)
rect1:addEventListener(Event.MOUSE_UP, onMouseUp, rect1)
 
rect2:addEventListener(Event.MOUSE_DOWN, onMouseDown, rect2)
rect2:addEventListener(Event.MOUSE_MOVE, onMouseMove, rect2)
rect2:addEventListener(Event.MOUSE_UP, onMouseUp, rect2)
 
function checkForIntersection(rectangle1, rectangle2)
 
   local function chkForRotated(r1, r2)
      local x1 = r2:getX()-r1:getX()
      local y1 = r2:getY()-r1:getY()
 
      local x2 = x1*math.cos(math.rad(r1:getRotation())) + y1*math.sin(math.rad(r1:getRotation()))
      local y2 = y1*math.cos(math.rad(r1:getRotation())) - x1*math.sin(math.rad(r1:getRotation()))
 
      local angle1 = math.cos(math.rad(r2:getRotation() - r1:getRotation()))
      local angle2 = math.sin(math.rad(r2:getRotation() - r1:getRotation()))
      local arr1 = { r2.width*angle1, -r2.height*angle2, r2.width*angle1 - r2.height*angle2}
      local arr2 = { r2.width*angle2, r2.height*angle1, r2.width*angle2 + r2.height*angle1}
 
      local minX = 0 
      local maxX = 0
      local minY = 0
      local maxY = 0
      for i=1,3 do
                if minX > arr1[i] then
                        minX = arr1[i]
                end
                if maxX <  arr1[i] then
                         maxX = arr1[i]
                end
                if minY > arr2[i] then
                        minY = arr2[i]
                end
                if maxY <  arr2[i] then
                         maxY = arr2[i]
                end
      end
 
      return x2 + maxX < 0 or x2 + minX > r1.width or y2 + maxY < 0 or y2 + minY > r1.height
   end
   return not (chkForRotated(rectangle1,rectangle2) or chkForRotated(rectangle2,rectangle1))
end
 
 function onEnterFrame(self, event)
    myvar = checkForIntersection(rect1, rect2)
    if myvar then
		rect1:setColorTransform(0,0,0,1)
    else
		rect1:setColorTransform(1,1,1,1)
	end
 end
 
 stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)

jdbc · April 2015

Your source code works fine!!

I had setAnchorPoint(0.5, 0.5), do you know how to change this code to work with this anchorpoint?

SinisterSoft · April 2015

Yes 0.5,0.5 is a must for that type of game - you also need to account for scaling possibly?

hgvyas123 · April 2015

no i don't know about how to change this code for anchorpoint .5,.5 but how about to set anchor point to 0,0 at the time of checking collision and resetting it to .5,.5 again once collision event finished. i guess it will do the job

jdbc · April 2015

no i don't know about how to change this code for anchorpoint .5,.5 but how about to set anchor point to 0,0 at the time of checking collision and resetting it to .5,.5 again once collision event finished. i guess it will do the job

I will try this. The anchorpoint must be 0.5, 0.5 for gameplay.

jdbc · April 2015

Finally the prototype is working with Box2d + XY scrolling to simply car movement. I have just used a array of tiles to generate the track.

It is based on http://appcodingeasy.com/Gideros-Mobile/Gideros-Camera-Move

Performance seems to be good on my BQ Android mobile.

totebo · April 2015

Hey @jbdc, looks good, but you need drift!

I did that in No Brakes by applying the force based on the rotation of an invisible sprite that had a slight slowness to it. It worked well, and a good substitute for "real" physics in a 0 gravity environment.

Nic

jdbc · April 2015

Hey @jbdc, looks good, but you need drift!

I did that in No Brakes by applying the force based on the rotation of an invisible sprite that had a slight slowness to it. It worked well, and a good substitute for "real" physics in a 0 gravity environment.

Nic

You can download source code from https://github.com/jdbcdev/topdown_racing and try to implement it. Feel free to use it.

Now I was trying that computer cars follow the right way.

jdbc · April 2015

I was reading this fantastic online book about Artificial Intelligence and Autonomous Agents to get a realistic movement of computer cars:

http://natureofcode.com/book/chapter-6-autonomous-agents/

In my case path following algorithm seems to be my solution.

jdbc · April 2015

I was moving computer car using path following algorithm, but it is not working in the third curve. Any idea? I was using my function TrackScene:updateCars() to get it.

jdbc · May 2015

Using the Path Following algorithm to provide computer car IA (yellow one, the blue is controlled by me)

totebo · May 2015

Nice!

jdbc · May 2015

Next step is to combine Avoid Collision and Path Following algorithm to achieve a more realistic car behaviour:

This is my entrypoint for Avoid Collision:
http://gamedevelopment.tutsplus.com/tutorials/understanding-steering-behaviors-collision-avoidance--gamedev-7777

I have tested with 4 cars and they are colliding at the beginning of the race.

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