Accelemeter

Games
#1

I am creating a game and I have found a lot of tutorials on how to make a object move using accelemter. Now how would I be able to make it collide and recieve points [import]uid: 39840 topic_id: 10618 reply_id: 310618[/import]

#2

Could you decribe what you’re wanting to achieve in more detail? I am not sure if I quite understand. If you are trying to make a game where the player collides with objects to increase their score than you should take a look at the “Simple Pool” example app here:
http://developer.anscamobile.com/content/simple-pool
[import]uid: 27965 topic_id: 10618 reply_id: 38603[/import]

#3

What are are wanting to know is called “Collision Detection”. There are several different ways and if you search the forums for “Collision Detection” you should get a lot of hits that will guide you.

There are two, well three basic models.

  1. Using Physics. If you use Corona SDK’s built-in physics you get collisions as events and you just have to set up an event handler to process the events. There are a ton of examples of this.

  2. Ignoring Physics. My game OmniBlaster doesn’t use physics, but it uses the Accelerometer to move the player’s ship. If you don’t use physics, there are two basic ways to check for collision:

2a. Check for overlapping rectangles.

local function hasCollided(obj1, obj2)  
 if obj1 == nil then  
 return false  
 end  
 if obj2 == nil then  
 return false  
 end  
 local left = obj1.contentBounds.xMin \<= obj2.contentBounds.xMin and obj1.contentBounds.xMax \>= obj2.contentBounds.xMin  
 local right = obj1.contentBounds.xMin \>= obj2.contentBounds.xMin and obj1.contentBounds.xMin \<= obj2.contentBounds.xMax  
 local up = obj1.contentBounds.yMin \<= obj2.contentBounds.yMin and obj1.contentBounds.yMax \>= obj2.contentBounds.yMin  
 local down = obj1.contentBounds.yMin \>= obj2.contentBounds.yMin and obj1.contentBounds.yMin \<= obj2.contentBounds.yMax  
 return (left or right) and (up or down)  
end

But if you’re using images that are more round in shape, that rectangle based check will cause false hits. Since many of my objects in my game are I use a 2nd collision detection method that is based on circular objects:

local function hasCollidedCircle(obj1, obj2)  
 if obj1 == nil then  
 return false  
 end  
 if obj2 == nil then  
 return false  
 end  
 local sqrt = math.sqrt  
   
 local dx = (obj1.x) - (obj2.x + 32);  
 local dy = (obj1.y) - (obj2.y + 32);  
   
 local distance = sqrt(dx\*dx + dy\*dy);  
 local objectSize = (obj2.contentWidth/2) + (obj1.contentWidth/2)  
 if distance \< objectSize then  
 return true  
 end  
 return false  
end

Most of the core code above was pulled from forum posts here! Credit to their original poster.

Rob [import]uid: 19626 topic_id: 10618 reply_id: 38612[/import]