How to tell when collision is finished

Questions
#1

I have another Lua question.

I am using kinetic collisions in my top-down grid based game, and I’m not really sure on the best way to tell when a collision has finished.

Each of the solid blocks in my game has four collision shapes, each in a different group. The groups are called up, down, left, and right. If player is colliding with left, it means it is to the left of a wall, and therefore cannot move right.

At the moment I have this:

function on_message(self, message_id, message, sender)
  if message_id == hash("contact_point_response") and if message.group == hash("left") then
touchingleft = true

and in my movement code:

elseif direction == "r" and not touchingleft then 
pos.x = pos.x + speed
go.set_position(pos)

But the obvious problem is that touchingleft is never set to false again. Any help? (when I change the type to “trigger”, I don’t get any contact_point_response messages, so that’s not worked for me)

#2

It should be ok to reset touchingleft at the end of every update() call. This is the same as how the ground contact variable is handled in the getting started tutorial.

#3

Britzl saves the day again. Although, I just realised that the reason that I can use triggers if i use “collision_response” instead of “contact_point_response” which is another easy way… I’ll try both. Thanks!

#4

Well, neither of these seem to work for me. I’m still investigating Britzl’s suggestion, but the triggers seemed to be a no starter. Is this code correct? I can’t

function on_message(self, message_id, message, sender)
if message_id == hash("collision_response") and message.group == hash("up") and message.enter then 
touchingup = true
print(message.enter)
elseif message_id == hash("collision_response") and message.group == hash("up") and not message.enter then 
touchingup = false
print(message.enter)
end

Because for me message.enter always returns nil.

#5

Okay, the correct code is with trigger_response rather than collision_response

function on_message(self, message_id, message, sender)
if message_id == hash("trigger_response") and message.group == hash("up") and message.enter then 
touchingup = true
print(message.enter)
elseif message_id == hash("trigger_response") and message.group == hash("up") and not message.enter then 
touchingup = false
print(message.enter)
end

Thanks, self!

1 Like
#6

… AAAAAAAaaaaand I’m stuck again.

I currently have collisions triggers that change four variables (touchingup, touchingdown… etc) to true or false depending on whether the collision is currently happening. They are working fine if I print those variables. However, the following code doesn’t work as I would expect.

The idea is that if "touchingdown"is true, the player is touching the lower part of a wall, and therefore can’t move up. But player should still be able to move down, left, or, right.

The problem that I have is that if “touchingdown” (or any of the other other touching variables) are true, none of the movement works at all.

code:

if direction == "u" and touchingdown == false then 
pos.y = pos.y + speed
go.set_position(pos)
elseif direction == "d" and touchingup == false then 
pos.y = pos.y - speed
go.set_position(pos)
elseif direction == "l" and touchingright == false then 
pos.x = pos.x - speed
go.set_position(pos)
elseif direction == "r" and touchingleft == false then 
pos.x = pos.x + speed
go.set_position(pos)
end
end

any ideas?

#7

It’s impossible to give advice with that snippet of code. It would be easier to help if we could see how touchingleft/right/up//down are changed.

What conclusions can you draw when your print the different values?