How to implement sprite climbing hill in box2d?

louis

I want to write a game, this game is a runner style, character climb up and down in hill.
My question,if I use box2d, I referred the giderios sample projfect "collision filtering",the ball always is up and down in ground ,how to implement to ball auto climb top height of hill, continue to move forward, not move back?

This is my favorite game:
https://play.google.com/store/apps/details?id=com.fingersoft.hillclimb

video:

Scouser

I think this will be the first game to be installed on my Nexus 4 when it arrives today

ar2rsawseen

well with Hill Climb Racing it's easy, you simply apply motor to the wheels and based on friction they drive up the hill.
But what do you mean by auto climb?

louis

Hill Climb Racing ,user control speed up, but in my game ,I want to character always running, don't need user speed up or brake, when character ran to a slope, according to angle,automatic speed down ,finally the character will be able to climb up ,and then run down from the top point, according to angle will be running faster and faster; character has infinite climb hill, down hill....

ar2rsawseen

Oh I get it now, here is something similar discussed here:
http://www.giderosmobile.com/forum/discussion/2331/can039t-stop-character-sliding-down-slope#Item_1

Edit:
scratch that, thats completely opposite (still can view for some ideas)

In your case, I think what you want to achieve is going app the slope with same speed?

That's an interesting one. You can try two approaches:
Apply constant force and remove friction
Or as you've mentioned detecting when you are on slope and applying more/less force.

So what exactly gives you the problems? Detection of slope, calculation of force? Or just looking if there is any easier solution?

hgvyas123

@louis :-

are u trying to make some what like tiny wings?

louis

Thanks,@ar2rsawseen ,@hgvyas123 ,

Actually, I'm newbie of box2d, so my question is very elementary, or very stupid,now I want to slove problems are:

1.how to detect slope,up,or down?
2. how to calculate body impulse? now I use body:applyLinearImpulse() method, has any better solution?
3. how to calculate and set character angle,when climb hill , body rotation 45 degree,down hill,body rotation -45 degree
4. how to remove bounce(jump more than once) of body when body land from air?

This is my test code:

--[[   This code is MIT licensed, see <a href="http://www.opensource.org/licenses/mit-license.php" rel="nofollow">http://www.opensource.org/licenses/mit-license.php</a> (C) 2010 - 2011 Gideros Mobile   ]]   require "box2d"   --b2.setScale(30)   -- this table holds the dynamic bodies and their sprites local actors = {}   -- create world local world = b2.World.new(0, 4)   -- create ground bitmap and add to stage local groundBitmap = Bitmap.new(Texture.new("ground.png")) groundBitmap:setAnchorPoint(0, 1) groundBitmap:setY(320) --stage:addChild(groundBitmap)       local function ground() -- create ground body local ground = world:createBody({})   ground:setPosition(0,0)   -- ground body is consists of 24 tiny edges local shape = b2.EdgeShape.new() local groundFilter = {categoryBits = 1, maskBits = 6}   local fixtures={} for x=0,480,20 do print(x) local x1 = x local x2 = x +20 local y1 = math.cos((x1 - 240) * 0.01) * 30 + 240 local y2 = math.cos((x2 - 240) * 0.01) * 30 + 240 --local y1=((x1 - 240) * 0.02)+240 --local y2=((x2 - 240) * 0.02)+240 print(y1,y2)   shape:set(x1, y1, x2, y2) local f=ground:createFixture({shape = shape, density = 1, filter}) fixtures[#fixtures+1]=f end return ground end   local g1=ground() local g2=ground()           -- create a circle body with given texture and collision filter and add it to stage local function createCircle(texture, x, y, filter) local body = world:createBody{type = b2.DYNAMIC_BODY, position = {x = x, y = y}}   local shape = b2.CircleShape.new(0, 0, 25) body:createFixture{shape = shape, density = 1, restitution = 0, friction = 0, filter = filter}   --body:setLinearDamping(10)   --body:applyTorque(100) --body:setAngularDamping(-10)   --[[ local sprite = Bitmap.new(Texture.new(texture, true)) sprite:setAnchorPoint(0.5, 0.5) stage:addChild(sprite) actors[body] = sprite ]]--   actors[body] = true   end   -- create circles local redFilter = {categoryBits = 2, maskBits = 3} local blueFilter = {categoryBits = 4, maskBits = 5}   createCircle("red-circle.png", 120, 240, redFilter) --createCircle("red-circle.png", 120, 100, redFilter) --createCircle("red-circle.png", 180, 100, redFilter)   createCircle("blue-circle.png", 480-60, 200, blueFilter) --createCircle("blue-circle.png", 480-120, 100, blueFilter) --createCircle("blue-circle.png", 480-180, 100, blueFilter)     local bgFarY local newFarY -- step the world and then update the position and rotation of sprites local function onEnterFrame() world:step(1/60, 8, 1)   for body,sprite in pairs(actors) do   body:applyLinearImpulse(0.025,0.025,body:getWorldCenter())   print(body:getPosition()) --[[ sprite:setPosition(body:getPosition()) sprite:setRotation(body:getAngle() * 180 / math.pi) ]]--     bgFarY = (bgFarY or 0) - ((8 or 4.0) / 4) print(bgFarY) --self.bgNearY = (self.bgNearY or 0) - ((self.bgspeed or 4.0))   newFarY = 480 -(-bgFarY) if newFarY <=0 then bgFarY = 0 g1:setPosition(bgFarY,0) else g1:setPosition(bgFarY,0) g2:setPosition(newFarY,0) end   end end     stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)     local debugDraw = b2.DebugDraw.new() world:setDebugDraw(debugDraw) stage:addChild(debugDraw)

louis

@hgvyas123 ,yes ,like tiny wings,any idea?

hgvyas123

i dont know about your game play heres the how tiny wing works

on the touch it is increasing gravity and on release it is setting gravity to normal you also need to continuos chk whether the force on body is not slow then any desired amount if yes apply some linearvelocity or force in x direction only and let box2d to convert it accordingly.

for the rotation i think this code can help

local sprite = Bitmap.new(Texture.new("a.png")) sprite:setAnchorPoint(0.5,0.5) sprite.lastX = sprite:getX() sprite.lastY = sprite:getY() sprite.angle = sprite:getRotation()   local angle = 0 local prevAngle = sprite:getRotation() local function onEnterFrame()   angle = math.atan2(sprite:getY() - sprite.lastY,sprite:getX() - sprite.lastX); angle = angle * (180/3.1428)   sprite.lastX = sprite:getX() sprite.lastY = sprite:getY()   sprite:setRotation(sprite:getRotation() + angle-prevAngle);   prevAngle = angle;   end stage:addEventListener(Event.ENTER_FRAME,onEnterFrame,stage)

to detect the slope you can chk the angle of our sprite

and to remove the bounce i think setting restitution parameter to 0 for both hill and sprite will work

ar2rsawseen

Similar to what @hgvyas123 said you can check out this tutorial for Objective-C
http://www.raywenderlich.com/3913/how-to-create-a-game-like-tiny-wings-part-2

techdojo

I think this will be the first game to be installed on my Nexus 4 when it arrives today

So you finally got yourself a new toy then?

Scouser

Yeah but the wife took the cat to the vet and got back 20 mins after they tried to deliver it yesterday

She is under orders not to leave the house today

techdojo

)
That would be so funny if wasn't too true far too often, especially with wives that seem to think their stuff is waaay more important.

Couldn't they deliver it to the office?

Scouser

It's been delivered so now I'm waiting for 5pm. Some companies will only deliver to the address the card is registered to.

Mells

@louis

3. how to calculate and set character angle,when climb hill , body rotation 45 degree,down hill,body rotation -45 degree

Similar to @hgvyas123 with code sample provided by @atilim so you can understand better what's happening :

-> Align Sprite Axis to Vector

sorry to be on-topic

hgvyas123

first forum where person have to say sorry for being on topic

)

Scouser

And rightly so )