Collision with any object

Max

Hello,
currently I'm trying to figure out how to check collision for an object without physics. The only problem I have at the moment is that I want an object to stop moving as soon as it hits any object, no matter which one. With the code I have at the moment I have to check for every single object if it collides with it. Is there a way to check if the object collides with any other object?
Thank you in advance.

totebo

I can recommend Bump. I played with it for a couple of hours, and it has a number of basic collision responses, including "touch" which seems to be what you're after.

https://github.com/kikito/bump.lua

antix

I also just discovered Splash yesterday. It's like Bump but can handle different shapes like circles too.
https://github.com/bakpakin/Splash.lua

But Bump is very powerful!

antix

My current experiment in Gideros uses Bump for collisions. If you are going to use a tilemap with Bump then maybe you will find this example project of use. It has two classes..

RenderLevel - Draws a tiled map. This class is based on the Desert example. Call render(map) to render a tiled map. It just draws tilemaps and in the code it has placeholder code for processing object and image layers as well. Subsequent calls to render() will attempt to dispose of any previously created resources.

CollisionMaker - Creates collision rectangles from a tiled map and adds them to a bump collision world. The main function you will call is createRectangles(map, name). map is a loaded tiled map and name is the name of the layer you want to make rectangles from. The function its-self It makes two passes over the layer, with the 1st pass creating vertical rectangles, and the 2nd pass creating horizontal rectangles. Each rectangle is created with a isWall bool variable to make it easy to differentiate them from other collision objects in bump. NOTE that the function treats any non zero tile as solid. Finally it adds the created rectangles to the bump collision world. Subsequent calls to createRectangles() will remove any previously added collision rectangles from the bump world. You can also just call reset() if you just want to clear the generated data.

Here is an example of how it works..

local world = require("bump").newWorld() -- CREATE NEW BUMP COLLISION WORLD   local func = loadfile("levels/test.lua") -- LOAD MAP local map = func() func = nil   local RenderLevel = RenderLevel.new() -- RENDER MAP RenderLevel:render(map) stage:addChild(RenderLevel)   local CollisionMaker = CollisionMaker.new(world) -- GENERATE COLLISION RECTANGLES CollisionMaker:enableDebug(true) CollisionMaker:createRectangles(map, "walls")

The attached picture shows the collision rectangles that are created by running the attached example project. As you can see, you could add another pass to optimize the rectangle output but it works as is just fine.

EDIT: See further down the thread for the updated example.

john26

I don't have much to add beyond the excellent suggestions above, but just take a step back to look at the theory of it. In principle there is no way to check if object A collided with any other objects (B, C, D etc) without looping over B, C, D and checking each one. What you can do is simplify the check. Eg if A, B, C, D are all strangely shaped objects (polygons) then checking a collision involves some complex mathematics for each pair. But you can be sure they didn't collide if you consider the rectangle that encloses eg A and B. If those rectangles didn't overlap, then no collision took place and you can skip to the next pairing. If the rectangles overlapped then you have to do the detailed calculation to see if the objects overlapped.

Another approach is to divide the game area into a grid and assign each object to one cell in the grid. Eg it might be quite coarse like 3x3 and A is in cell (1,2) and B is in cell (3,3). In this case you can be sure A and B are not colliding as they are in different cells (and not neighbouring cells). The disadvantage of this is you need to constantly update the cell index number for each object but it means many collision tests can be avoided.

The point is you can write your own collision detection code right in Lua. It is not necessarily better to use Box2D or other libraries. If you are doing something simple, complex libs could slow things down while 2-3 lines of Lua code is often faster.

This tutorial provides great info on collision detection.
http://www.metanetsoftware.com/technique/tutorialA.html

antix

@john26, great explanations
I still wholeheartedly recommend bump for grid based games. I twrote my own collision engine and whilst it is pretty good, it doesn't come close to bump by a long way. If I had discovered bump before writing my own collision engine, I would have saved 3 weeks heheh. Good article link

If you want to go down the SAT path then here are some other links.

https://bitbucket.org/RudenkoPaint/sat-lua - I haven't looked at this closely but it's another library from the looks of it.
http://www.phailed.me/2011/02/polygonal-collision-detection/ - This one has a simple explanation of SAT and has LUA source code too.

There is also a rather cool library called HardonColider which uses SAT. Its hard to get working with Gideros (don't even go there) but it has some great code and there's a lot to learn from reading through it. https://vrld.github.io/HardonCollider/.

You can find a few others collision libraries at https://love2d.org/wiki/Category:Libraries. In general it's a great place to go (check out their forums too) to find code and stuff. Love2D is LUA based and "most" of the things you will find there are fairly easy to get working with Gideros (except HardonCollider ROFLS)

And here's a neat little blog about circle collision/resolution with LUA code too.. http://blogs.love2d.org/content/circle-collisions

And finally this series of articles is pretty good at showing how to make a Mario style platform collision engine... https://www.raywenderlich.com/15230/how-to-make-a-platform-game-like-super-mario-brothers-part-1

antix

I took a day off from my current project to mess about and chose to dig up my HardOnCollider experiment and post it as another example of collision detection. I've tidied it up a bit and added a tiled map loader which loads tiled maps and creates collision data from objects in any objectlayer.

If you run the attached project you can click and drag the ball around the screen, which will turn red when it collides with a shape. The ball will also be pushed out of any shape that it collides with and a little white arrow will show the direction of the collision.

EDIT: See further down the thread for the updated Hardon Collider example.

rolfpancake

@antix
Thanks a ton for your links and the attached project!
(A central place for tutorial links would be great anyway)

muro

@antix thanks a lot for your great answers

dreiko65

@antix You are awesome. The project you have just upload is exactly what I ve been looking for a while now. Thanks for sharing.

antix

You're welcome

@misterhup has another discussion about collisions and I posted another example project there. http://giderosmobile.com/forum/discussion/6357/bump#Item_1

I'll re-post it here so all my examples are in the one thread....

Okay here is a little example project that can detect collisions between rotated rectangles. The collision stuff is from this page.. https://bitbucket.org/RudenkoPaint/sat-lua. The version included here has been modified slightly to better work with Gideros. It's a bit messy but it works.

When you run the example project you can click and drag one of the boxes around. If it collides with the other, both turn red.

NOTE: The example is fairly basic and does not perform any collision resolution but with a bit of work it could easily do so. The "response" table in the main loop contains pretty much everything you need to resolve the collisions.

Anyway, it should be enough to get you up and running

EDIT: See further down the thread for the updated example..

totebo

Hey @antix, how does SAT compare to Bump, performance wise? I'm using Bump in a shooter I'm working on and it's really quite fast and does what I want it to (resolves collisions).

antix

@totebo - SAT is slower because needs to use a ton of maths to project vectors and stuff when determining if collisions happened. Add to that having to rotate all those vertices when you rotate a polygon and it adds up. Once you start using large numbers of polygons, bump really outshines a SAT solution like the example in my post above.

at the end of the day, if you aren't rotating rectangles, then use bump! It's just fantastic!

I updated my example while I was away for the wekeend (as well as my examples in the other thread (Hardon Collider, and Bump Collision Maker). I've added some small documentation to the top of the code and also in the classes I have provided. Most of the classes have been revamped and I'm pretty happy how they ended up. I'm surprised at how much I got done without any internet to distract me heheh.

Here is the latest incarnation of the SAT example..

--[[   SAT Rectangle Collision Example for Gideros by Cliff Earl Antix Software March 2016   Example project that creates and displays 2 rotating boxes that can be dragged about the screen by their center points, and detects collisions between them.   Collision detection is a 2 part process. First the bounding boxes are checked to see if they overlap (it is pointless to waste CPU time on SAT calculations unless that is the case). Once the boxes overlap they will be tinted yellow and SAT collision detection will then be applied to test for intersection (one rectangle partially inside the other rectengle). If the rectangles do intersect then they will be tinted red.   There is one class (Draggable) and 1 library (GSAT) included in the example.   Draggable An extension of Bitmap that can be dragged about by its center. See Draggable.lua for more information.   GSAT A simple library for performing collision detection (and projection-based collision response) of rectangular shapes in 2 dimensions. See GSAT.lua for more information.   --]]   --require("mobdebug").start() -- ONLY REQUIRED FOR ZEROBRANE   local GSAT = require("gsat") -- THE COLLISION LIBRARY   local function newBox(actor) -- CREATE A NEW COLLISION BOX local x, y, w, h = actor:getBounds(stage) local box = GSAT.Box(x + (w * 0.5), y + (h * 0.5), w, h) box:setRotation(actor:getRotation()) return box end   local function actorInActor(actor1, actor2) -- TEST 2 BOUNDING BOX FOR OVERLAP local x, y, w, h = actor1:getBounds(stage) local x2, y2, w2, h2 = actor2:getBounds(stage) return not ((y+h < y2) or (y > y2+h2) or (x > x2+w2) or (x+w < x2)) end   local info = TextField.new(nil, "Drag the boxes by their centers to move them") info:setPosition(20, 20)   local player = Draggable.new(Texture.new("images/box.png", true), {x = 160, y = 128}) -- CREATE PLAYER player.box = newBox(player) player.onDragged = function() player.box:setPosition(player:getPosition()) end   local enemy = Draggable.new(Texture.new("images/box.png", true), {x = 160, y = 352}) -- CREATE ENEMY enemy.box = newBox(enemy) enemy.onDragged = function() enemy.box:setPosition(enemy:getPosition()) end   local function onEnterFrame(event) -- MAIN LOOP   local angle = enemy:getRotation() - 0.284 -- ROTATE ENEMY CCW enemy:setRotation(angle) enemy.box:setRotation(angle)   angle = player:getRotation() + 0.284 -- ROTATE PLAYER CW player:setRotation(angle) player.box:setRotation(angle)   if actorInActor(player.box, enemy.box) then stage:setColorTransform(1, 1, 0, 1) -- BOXES OVERLAP, TINT YELLOW   local response = GSAT.Response() -- CHECK FOR COLLISION BETWEEN BOXES local collided = GSAT.checkCollision(player.box, enemy.box, response) if collided then stage:setColorTransform(1, 0, 0, 1) -- BOXES COLLIDED, TINT BOXES RED   -- -- PERFORM COLLISION RESOLUTIONS HERE --   end else stage:setColorTransform(1, 1, 1, 1) -- NO COLLISION, TINT BOXES BACK TO NORMAL end   end   stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)   stage:addChild(enemy) stage:addChild(player)   stage:addChild(info)

antix

Here is the updated Collision Maker example..

--[[   CollisionMaker Example for Gideros by Cliff Earl Antix Software March 2016   Example project that loads a tiled map, renders it, and creates collision rectangles from one of its layers (which are then added to a bump world).   bump is a collision detection and resolution library that operates on AABB's (Axis Aligned Bounding Boxes), it can also be used as a spatial directory complete with query functions. You can read more about bump.lua and its functionality at <a href="https://github.com/kikito/bump.lua" rel="nofollow">https://github.com/kikito/bump.lua</a>   Take the following case where a map is a 3x3 grid where 1 represents a solid cell and 0 represents an empty cell. You want your sprites to collide and not pass through any solid cells. You could create a new collision rectangle for each solid grid cell which would result in 6 collision rectangles. It would be more efficient (and faster) to create fewer (but bigger) collision rectangles. This is what CollisionMaker does. CollisionMaker first scans each vertical column of grid cells in the map layer and creates collision rectangles from them. It then makes a second pass and creates horizontal collision rectangles from the remaining solid grid cells. So in the following example CollisionMaker would generate only 3 collision rectangles. I hope you can see the benefit of CollisionMaker.   1,1,1 1,0,0 1,1,0   2 classes are provided with this example, RenderLevel, and CollisionMaker...   RenderLevel. Loads tiled maps and renders them. RenderLevel is an extension of the Sprite class so once you have called render() it can be directly added to the stage. When calling render() any previously created resources (sprites, etc) will be cleaned up so you can reuse the RenderLevel over and over.   CollisionMaker. Scans named layer and creates collision rectangles from it. Any generated collision rectangles are added to a bump world. CollisionMakers generation technique is explained above. When you call createRectangles() any previously created collision rectangles will be removed from the bump world so it also can be reused over and over. When adding a collision rectangle to the bump world, CollisionMaker sets its isWall bool to true, which can be used during collision detection / resolution.   NOTES:   If you examine the RenderLevel code you will see placeholder code where you can expand its functionality to process objectlayers and imagelayers.   --]]   --require("mobdebug").start() -- ONLY REQUIRED FOR ZEROBRANE STUDIO   local RenderLevel = RenderLevel.new() -- CREATE RENDERLEVEL   local world = require("bump").newWorld() -- CREATE BUMP COLLISION WORLD   local func = loadfile("levels/level0000.lua") -- LOAD MAP local map = func() func = nil   RenderLevel:render(map) -- RENDER MAP stage:addChild(RenderLevel)   local CollisionMaker = CollisionMaker.new(world) -- GENERATE COLLISION RECTANGLES CollisionMaker:enableDebug(true) CollisionMaker:createRectangles(map, "walls")

antix

And finally here is the updated Hardon Collider example..

--[[   Hardon Collider Example for Gideros by Cliff Earl Antix Software March 2016   Example project that loads a tiled map, renders it, and creates collision shapes from one of its layers and adds those to a Hardon Collider world. It also updates the Collision world which detects collisions and performs basic collision resolution by pushing the draggable ball shape out of any wall shape that it collides with.   Hardon Collider is a Love2d library that detects collisions between circles, polygons (convex and concave), and points. You just add collision shapes to the collider, update it every frame, and then respond to collisions via a callback fundtion. The version of Hardon Collider provided with this example is a version that has been modified to work with Gideros. You can read more about Hardon Collider at <a href="https://vrld.github.io/HardonCollider/" rel="nofollow">https://vrld.github.io/HardonCollider/</a>   Besides the Hardon Collider library (and its many associated lua files) 1 class is provided, Level...   Level A Sprite extension that can load tiled maps. It creates collision shapes for objects in objectlayers of the type "solid". These collision shapes are then added to the Hardon Collioder world. It can also creates a graphical shape (Gideros Shape) for each collision shape it creates. See Level.lua for more information.   --]]   --require("mobdebug").start() -- ONLY REQUIRED FOR ZEROBRANE   require("json")   local currentTimer = 0   local COLLIDER = HC.new(100) -- CREATE NEW COLLISION WORLD   local Level = Level.new({collider = COLLIDER, createShapes = true}) -- LOAD A MAP Level:loadMap("level0000") Level:toFront()   local x, y = Level:getPlayerStart() -- CREATE A BALL OBJECT local ball = Bitmap.new(Texture.new("images/ball.png", true)) ball:setAnchorPoint(0.5, 0.5) ball.shape = COLLIDER:addCircle(x, y, ball:getWidth() * 0.5) ball.position = ({x = 0, y = 0}) ball:setPosition(x, y) stage:addChild(ball)   local arrow1 = Bitmap.new(Texture.new("images/arrow.png", true)) -- SOME RANDOM ARROW arrow1:setAnchorPoint(0.5, 0.5) arrow1:setRotation(0) arrow1:setPosition(x, y) arrow1:setVisible(false) stage:addChild(arrow1)   local DEBUG = TextField.new(nil,"") -- JUST TO SOW A FEW VARS DEBUG:setPosition(0, 64) stage:addChild(DEBUG)   local function onCollision(dt, shape_a, shape_b, mtv_x, mtv_y) -- CALLED WHEN COLLISION DETECTED local floor, radToDeg, atan2 = math.floor, 180/ math.pi, math.atan2   local ball_shape, tileshape -- sort out which one our ball shape is if shape_a == ball.shape and shape_b.type == "tile" then ball_shape = shape_a elseif shape_b == ball.shape and shape_a.type == "tile" then ball_shape = shape_b else return -- NONE OF THE TWO SHAPES IS A TILE <img class="emoji" src="https://forum.gideros.rocks/resources/emoji/frowning.png" title=":(" alt=":(" height="20" /> end   local angle = ( ( atan2(mtv_y, mtv_x) * radToDeg ) -90) % 360 -- ANGLE OF COLLISION   ball_shape:move(mtv_x, 0) -- CORRECT COLLISION SHAPE X, Y ball_shape:move(0, mtv_y)   local fx, fy = ball_shape:center() -- CORRECT BALL X, Y ball.position.x = fx ball.position.y = fy ball:setPosition(fx, fy) ball:setColorTransform(1, 0, 0, 1)   arrow1:setVisible(true) arrow1:setPosition(fx, fy) arrow1:setRotation(angle)   DEBUG:setText(" angle="..floor(angle)..", mtv_x="..floor(mtv_x)..", mtv_y="..floor(mtv_y)) end   local function screenTouched(e) -- TELEPORT THE BALL TO WHERE THE SCREEN IS TOUCHED local x, y = e.touch.x, e.touch.y ball.shape:moveTo(x, y) ball:setPosition(x, y) ball:setColorTransform(1, 1, 1, 1)   arrow1:setVisible(false) DEBUG:setText("") end   local function onEnterFrame(event) -- MAIN GAME LOOP local timer = os.timer() local dt = timer - currentTimer   COLLIDER:update(dt) -- UPDATE COLLISION WORLD end   COLLIDER:setCallbacks(onCollision) --SET COLLISION WORLD CALLBACK   stage:addEventListener(Event.ENTER_FRAME, onEnterFrame) stage:addEventListener(Event.TOUCHES_BEGIN, screenTouched) stage:addEventListener(Event.TOUCHES_MOVE, screenTouched)

totebo

Cool, thanks! I think I have to use Hardon or SAT, because I have an isometric world. Unless I can rotate ALL rectangles 45 degrees somehow!

Out of SAT and Hardon, which is more efficient when it comes to rectangle collisions?

antix

@totebo - It's hard to say. I didn't write either of those systems, just the examples that show their basic use.

Hardon Collider actually uses GJK to detect rectangle collisions. It also utilizes a spatial hash like bump to increase it's performance. In my own tests I found Hardon Collider kind of slow but I was using 640 polygons for my walls in that experiment.

the SAT example has no spatial hash so if you get to larger numbers of polygons the performance will degrade unless you implement some spatial hash or other algorithm to reduce collision checks.

For an isometric game, bump should be all you require. I would think all collisions get handled by bump and then world objects are translated when drawn to appear to be in the correct perspective.

It's an interesting question (about isometric collision) and one I could easily get side-tracked by [-X

@jdbc shares some code for translation in his thread http://giderosmobile.com/forum/discussion/6054/isometric-endless-racing#Item_1 Check it out

totebo

Keeping the collisions non-rotated and separated from the gfx is a great idea. And worth side tracking I reckon. Although isometric is probably a little tricky, because the perspective is usually a bit "squashed", which means the actual collisions would be diamonds rather than right-angled rectangles. Unless there is some " right-angle-ification" going on.

misterhup

@antix I have to say, is really impressive what SAT can do, but isn't there a way to play with the object's anchor point? It seems that SAT doesn't allow scaling or changing the anchor point of a box. It seems that that's the only thing it is missing. I could be wrong tho, it won't be the first time )

antix

Perspective is the key word here. It doesn't matter what perspective you draw objects in, the underlying square grid system remains the same, and valid.

pie

thanks for sharing @antix, I still don't need collisions but I am sure that this post will come in handy...

I think it deserves to be moved to the Code Snippet section of the forum (if not included in a resource list inside the docs) to be easily found later.

antix

Okay so I really am trying to avoid the stuff I should be doing (like exciting old scene management code *yawn*) so I have bashed together a little demonstration of Bump collision working with Isometric rendering...

--[[   ISO Collision Utilizing Bump.lua Example by Cliff Earl Antix Software March 2016   This example serves to illustrate that you do not need to rotate or perform any other hanky operations to perform collision detection in an isometric game.   The key point is that you don't ever need any isometric to cartesian calculations since everything takes place in a grid that uses cartesian coordinates. You only need to convert from cartesian to isometric to draw your game world and objects.   This example draws a small isometric tile map to the screen. As it draws the map it creates a collision rectangle for any tile that is solid (1 in this example) and adds it to a bump collision world. It then creates 5-12 colored squares that move at a random speed at a random angle. In the main loop the squares are moved and collisions checked in the bump world. Any square that hits a wall will be bounced off the wall.   As you will see, it does not matter how you want to draw your game objects. They can be drawn in isometric perspective, topdown, side on, etc. As long as the world you want to use is based on a grid filled with AABB's (Axis Aligned Bounding Boxes), bump will work perfectly fine for collision detection and resolution.   NOTES: This example uses the twoDToIso() code posted by jdbc in his thread about his Endless Isometric Racing Game...   <a href="http://giderosmobile.com/forum/discussion/6054/isometric-endless-racing#Item_2" rel="nofollow">http://giderosmobile.com/forum/discussion/6054/isometric-endless-racing#Item_2</a>   --]]   --require("mobdebug").start() -- ONLY REQUIRED FOR ZEROBRANE STUDIO   stage:setOrientation(Stage.LANDSCAPE_LEFT)   local random, sin, cos, rad = math.random, math.sin, math.cos, math.rad   math.randomseed(os.time()) for i = 1, 4 do random() end -- INIT PRNG   local function vector2(x, y) -- CREATE A NEW 2D VECTOR return {x = x, y = y} end   WIDTH = application:getContentWidth() -- SOME NASTY CONSTANTS HEIGHT = application:getContentHeight() MIDX = WIDTH * 0.5 - 32 MIDY = HEIGHT * 0.5   TILESIZE = 32   ACTORSIZE = 16   MAPWIDTH = 7 MAPHEIGHT = 7   local bumpWorld = require("bump").newWorld() -- CREATE BUMP COLLISION WORLD   local textureRegions = { { 0, 0, 64, 32}, -- 1 WALL TILE { 64, 0, 64, 32}, -- 2 DIRT TILE {128, 0, 64, 32}, -- 3 GRASS BUTTON {192, 0, 32, 16}, -- 4 BLUE ACTOR {192, 16, 32, 16}, -- 5 RED ACTOR {224, 0, 32, 16}, -- 6 CYAN ACTOR {224, 16, 32, 16}, -- 7 YELLOW ACTOR }   local textureAtlas = Texture.new("images/isoblocks.png", true)   local function newRegion(r) -- RETURNS A NEW TEXTURE REGION local a = textureRegions[r] return TextureRegion.new(textureAtlas, a[1], a[2], a[3], a[4]) end   local function setRegion(bitmap, r) -- SETS A BITMAPS TEXTURE REGION local region = bitmap.region local a = textureRegions[r] region:setRegion(a[1], a[2], a[3], a[4]) bitmap:setTextureRegion(region) end   function newBitmap(r) -- CREATE NEW BITMAP local a = textureRegions[r] local region = TextureRegion.new(textureAtlas, a[1], a[2], a[3], a[4]) local bitmap = Bitmap.new(region) bitmap.region = region -- bitmap:setAnchorPoint(0.5, 0.5) return bitmap end   local function twoDToIso(x, y) -- FROM <a href="http://giderosmobile.com/forum/discussion/6054/isometric-endless-racing#Item_2" rel="nofollow">http://giderosmobile.com/forum/discussion/6054/isometric-endless-racing#Item_2</a> local isoX = x -y local isoY = (x + y) * 0.5 return isoX, isoY end   local function setISOPosition(actor, x, y, w) -- SET BITMAPS X, Y POSITION IN ISOMETRIC SPACE local isoX = (x + (w)) - y local isoY = (x + y) * 0.5   actor:setPosition(isoX + MIDX, isoY) end   local function initMap(group, mapData) -- CREATE GRAPHIC OBJECTS AND COLLISION RECTS FOR TILE MAP local n = 1 for r = 0, MAPHEIGHT - 1 do for c = 0, MAPWIDTH - 1 do local tile = mapData[n] -- GET NEXT TILE if tile == 1 then -- IF ITS A SOLID TILE, CREATE A COLLISION RECT AND ADD IT TO THE BUMP WORLD local rect = {isWall = true, x = c * TILESIZE, y = r * TILESIZE, w = TILESIZE, h = TILESIZE} bumpWorld:add(rect, rect.x, rect.y, rect.w, rect.h) end local bitmap = newBitmap(tile) local x, y = twoDToIso(c * TILESIZE, r * TILESIZE) -- CONVERT FROM CART TO ISO bitmap:setPosition(x + MIDX, y) -- SET ACCORDING TO ISO POSITION group:addChild(bitmap) n = n + 1 -- NEXT TILE TO FETCH end end end   local function redrawMap(group, mapData) -- REDRAW THE TILE MAP (NOT USED IN EXAMPLE) local n = 1 for r = 1, MAPHEIGHT do for c = 1, MAPWIDTH do local tile = mapData[n] local bitmap = group:getChildAt(n) setRegion(bitmap, tile) -- SET BITMAPS NEW REGION n = n + 1 end end end   local mapData = { -- MOST AWESOME TILE MAP EVER 1,1,1,1,1,1,1, 1,2,1,2,2,2,1, 1,2,2,2,1,2,1, 1,2,2,2,2,2,1, 1,1,2,3,2,2,1, 1,2,2,2,2,2,1, 1,1,1,1,1,1,1, }   local mapGroup = Sprite.new() stage:addChild(mapGroup)   initMap(mapGroup, mapData)   local actors = {}   local function createActor() local actor = newBitmap(random(4, 7)) stage:addChild(actor) local x = (TILESIZE * 3) + random(0, 16) local y = (TILESIZE * 4) + random(0, 16)   bumpWorld:add(actor, x, y, ACTORSIZE, ACTORSIZE)   local speed = random(12, 20) local angle = random(0, 360) actor.velocity = vector2(speed * cos(rad(angle - 90)), speed * sin(rad(angle - 90))) actor.position = vector2(x, y)   setISOPosition(actor, x , y, ACTORSIZE) table.insert(actors, actor) end   for i = 1, random(5, 12) do -- CREATE A RANDOM NUMBER OF ACTORS createActor() end   local currentTimer = 0 local function onEnterFrame(event) -- MAIN LOOP local timer = os.timer() local dt = timer - currentTimer currentTimer = timer   local function updateActor(actor, dt) -- UPDATES ACTOR local p, v = actor.position, actor.velocity -- GET POSITION AND VELOCITY   p.x = p.x + v.x * dt -- MOVE ACTOR TO ITS DESIRED POSITION p.y = p.y + v.y * dt   local filter = function(item, other) if other.isWall then return "bounce" end -- ONLY CHECK FOR WALLS IN EXAMPLE end   local actualX, actualY, cols, len = bumpWorld:move(actor, p.x, p.y, filter) p.x, p.y = actualX, actualY   for i=1,len do -- BOUNCE ACTOR OFF WALLS local col = cols[1] local bounciness = 1 local nx, ny = col.normal.x, col.normal.y local vx, vy = v.x, v.y if (nx < 0 and vx > 0) or (nx > 0 and vx < 0) then vx = -vx * bounciness end if (ny < 0 and vy > 0) or (ny > 0 and vy < 0) then vy = -vy * bounciness end v.x, v.y = vx, vy end setISOPosition(actor, p.x, p.y, ACTORSIZE) end   for i = #actors, 1, -1 do -- MOVE ACTORS ABOUT MAP AND BOUNCE THEM OFF WALLS updateActor(actors[i], dt) end   end   stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)

totebo

Wow! Look forward to giving this a spin after the holidays. You really ARE trying to avoid doing something else aren't you? Awesome.

antix

Sure am, but now I ran out of excuses so I'll get cracking on scene management now

totebo

Hey @antix, I've downloaded all these, really cool stuff.

I now need to do something slightly different; skewing the perspective. With your Legendary Antix Hat on, how would I even start doing something like this? See illustration.

antix

@totebo, having everything conform to a grid makes things a lot easier. Bump can of course handle any shapes you like. Does your isometric game have different sized tiles?

totebo

The game I'm building has an isometric perspective, but it's not divided into rigid tiles. The objects requiring collisions are of varying sizes, like the mockup above. I've started creating a test for this, but at the moment I feel like a blind man in a dark room.

antix

@totebo, oops didn't see your pictures (cleans glasses)

The actual collisions can still take place in the bump world and you can do some mathsy translation to determine where the objects should be drawn onscreen I think.

So I took a break and made an example. There are some actors which move about the screen and bounce off the walls and each other. They are drawn in a skewed perspective.

--[[   Skewed Perspective Collision utilizing Bump.lua Example by Cliff Earl Antix Software April 2016   Here is another wee example to show you can have many different sized rectangles colliding in a bump world and draw them in any crazy way you like. At the end of the day you just need to use some maths to translate the coordinates from bump to draw your objects on screen how you want them.   The function of note in this example is setSkewedPosition(). It transforms cartesian coordinates to the desired skewed coordinates for positioning sprites on screen.   It is really that simple I think <img class="emoji" src="https://forum.gideros.rocks/resources/emoji/smile.png" title=":)" alt=":)" height="20" />   --]]   --require("mobdebug").start() -- ONLY REQUIRED FOR ZEROBRANE STUDIO   stage:setOrientation(Stage.PORTRAIT) local random, insert, sin, cos, rad = math.random, table.insert, math.sin, math.cos, math.rad math.randomseed(os.time()) for i = 1, 4 do random() end -- INIT PRNG   local function vector2(x, y) -- CREATE A NEW 2D VECTOR return {x = x, y = y} end   local bumpWorld = require("bump").newWorld() -- CREATE BUMP COLLISION WORLD   local shapes = { {texture = Texture.new("images/big.png", false), w = 32, h = 32}, {texture = Texture.new("images/med.png", false), w = 16, h = 16}, {texture = Texture.new("images/sml.png", false), w = 8, h = 8}, }   local function setSkewedPosition(actor, x, y) -- SET BITMAPS X, Y POSITION IN SKEWED ISOMETRIC SPACE local skewedX = x + (y / 2) actor:setPosition(skewedX, y) end   local walls = { {isWall = true, x = 0, y = 0, w = 192, h = 8}, -- TOP {isWall = true, x = 0, y = 184, w = 192, h = 8}, -- BOTTOM {isWall = true, x = 0, y = 8, w = 8, h = 176}, -- LEFT {isWall = true, x = 184, y = 8, w = 8, h = 176}, -- RIGHT } for i = 1, #walls do bumpWorld:add(walls[i], walls[i].x, walls[i].y, walls[i].w, walls[i].h) -- ADD WALLS TO BUMP AS COLLISION RECTANGLES end stage:addChild(Bitmap.new(Texture.new("images/walls.png", false))) -- LETS JUST SHOW AN IMAGE INSTEAD OF DRAWING <img class="emoji" src="https://forum.gideros.rocks/resources/emoji/wink.png" title=";)" alt=";)" height="20" />   local actors = {}   local function createActor(x, y) local shape = shapes[random(#shapes)] -- GET A RANDOM SHAPE   local actor = Bitmap.new(shape.texture) stage:addChild(actor) actor:setColorTransform(random(), random(), random(), 1) -- RANDOMIZE ITS COLOR bumpWorld:add(actor, x, y, shape.w, shape.h)   local speed = random(12, 20) -- SET ACTOR IN MOTION local angle = random(0, 360) actor.velocity = vector2(speed * cos(rad(angle - 90)), speed * sin(rad(angle - 90))) actor.position = vector2(x, y) actor.isShape = true   setSkewedPosition(actor, x , y) -- MAGIC insert(actors, actor) end   createActor( 24, 24) -- CREATE 9 ACTORS OF RANDOM SIZES createActor( 80, 24) createActor( 136, 24) createActor( 24, 80) createActor( 80, 80) createActor( 136, 80) createActor( 24, 136) createActor( 80, 136) createActor( 136, 136)   local currentTimer = 0 local function onEnterFrame(event) -- MAIN LOOP local timer = os.timer() local dt = timer - currentTimer currentTimer = timer   local function updateActor(actor, dt) -- UPDATES ACTOR local p, v = actor.position, actor.velocity -- GET POSITION AND VELOCITY   p.x = p.x + v.x * dt -- MOVE ACTOR TO ITS DESIRED POSITION p.y = p.y + v.y * dt   local filter = function(item, other) if other.isWall or other.isShape then return "bounce" end -- ONLY CHECK FOR WALLS IN EXAMPLE end   local actualX, actualY, cols, len = bumpWorld:move(actor, p.x, p.y, filter) p.x, p.y = actualX, actualY   for i=1,len do -- BOUNCE ACTOR OFF WALLS local col = cols[1] local bounciness = 1 local nx, ny = col.normal.x, col.normal.y local vx, vy = v.x, v.y if (nx < 0 and vx > 0) or (nx > 0 and vx < 0) then vx = -vx * bounciness end if (ny < 0 and vy > 0) or (ny > 0 and vy < 0) then vy = -vy * bounciness end v.x, v.y = vx, vy end setSkewedPosition(actor, p.x, p.y) end   for i = #actors, 1, -1 do -- MOVE ACTORS ABOUT MAP AND BOUNCE THEM OFF WALLS updateActor(actors[i], dt) end end   stage:addEventListener(Event.ENTER_FRAME, onEnterFrame)

The sprites in the example are predrawn skewed as I think I read in one of your other threads that skewing with matrix is bugged right now (like my beloved RenderTarget:clear()

totebo

Amazing! Worked something similar up myself, but this is great for reference. The magic for me was the x=x+y. Thanks a lot @antix, you're too easy to distract!

antix

@totebo, I had programmers block on my current experiment so it was useful to take some time off and make some examples yesterday to help other users with their coding problems. Taking a wee rest has me back on track now though ~:>