PMO collision with background objects

[DavidN]

I can't remember who has the source for the PMO just now, but in going back to one of my earlier games, I've found that in the Flash version, the PMO doesn't work correctly with background objects that aren't rectangular - the character collides with the entire bounding box of the object.

You can see its behaviour on the ramps here:

http://www.clickteam.info/davidn/games/flashtesting/pmoramps.html

http://www.clickteam.info/davidn/games/flashtesting/pmoramps.mfa

[netninja]

Yeah that's definitely not working the same.

[AndyH]

Hi David

I have been using PMO and didn't see this behaviour so it was a strange one.

However I found the cause is that the player DOES NOT have fine collision detection enabled. In the MMF runtime this causes a box collision of the player with a fine pixel perfect collision with the background object. In the Flash runtime it looks like if the active object is in box collsion mode then it tests for a box collision on the background object too, which is what we see.

Putting fine collision detection on the player and it all works.

I'm sure I read something about this a while back, but I do no recall if it was a bug to be fixed or a limitation of the flash version.

One thing is for sure, if you have box collision on your active object it will test for box collisions against background objects. I've just tested this with the 8-way movement and the collision detection is the same, so it's not to do with the PMO but the way MMF Flash deals with collisions.

The solution is to use fine collision on all obects, but would be interested to know if the collision issue is a known bug or limitation and if it is something that can be fixed?

[DavidN]

Ah...! You know, now that you mention that, I remember a thread about fine detection against actives and backdrops as well. I had actually checked the objects in the game that this example came from and thought that fine detection was turned off on my collider object, but later on I found that what I thought was the collider was in fact an object that just followed the player sprite around, and the player sprite was just the collider as well. I'm still not sure why I might have done that, but it was five years ago so I might just have been slightly stupider at the time.

Thanks for pointing that out - I didn't put the two things together. I'd already made changes to the game to avoid the problem coming up, but it's good to know for anyone else who sees this!