Why do some carpet tiles change when items are dropped on it while others do not?

Question

I am not sure if this is a bug or not, but why is it that some of the carpet tiles in game (carpets that are already on the floor as seen in pictures below) will vanish when items are dropped on them while others do not?

Below are two tiles that I found immediately that disappear when items are dropped. On the right side of the screen, you can see that I used the browse field function to show the items dropped on the tile in question.

Below I am adding additional pictures of other carpet tiles that did not disappear when the same amount of items were dropped.

Answer 1

TL;DR: There are two different versions of the red carpet, they have different properties which will make one disappear, but not the other. The places where you can hide them probably use the wrong version by mistake, but that's hard to prove. 

Objects in Tibia have several parameters (flags) which control how the behave in the environment, what can and cannot be done to them, how they look, etc. The difference between these carpets has nothing to do with the fact that they are carpets, but only on the flags that were assigned to them. 

There are some flags of objects which will prevent them from disappearing on stacks. For example, a flag called "bank", which is used on objects which are used as floors and have a "speed". Another flag is "clip", which is used for objects which are on the floor but aren't floor themselves (most of those objects don't occupy the full 32x32 tile too, allowing you to see the floor underneath). Another relevant flag here is the "unmove" flag, which as you can imagine, prevents that object from being moved. 

Most floor decorations have the Clip flag, which ensures they aren't hidden on stacks. There is a version of the red carpet that doesn't have the Clip flag (and one that does). This is the version used in the places where you can hide them. 

There aren't many objects which cannot be moved, don't have the clip flag and are used on places where you can throw items at. For example, several objects with those flags are used to decorate walls, but you can't throw items on walls, so you can't see that effect. There are some others though, for example, this place in Issavi has some unmovable pillows which also don't have the clip flag, so you can hide them:

Now, this leads to the question of why is it that two different versions of the red carpet exist, and honestly, I don't know. Many objects in Tibia are "duplicated" (sometimes with slightly different flags). Usually it's not hard to tell why, but in this case I can't really see why they would create the second version. It does seem to be (initially) related to the Explorer Society, however, but visiting their offices didn't give me any insight. 

One possible reason is that version of the red carpet was initially only used in the Explorer's Society locked rooms, so they really didn't care since they were not reachable. With time, they ended up using the "wrong" version in accessible places such as the revamped Thais Boat and Adventurer's guild, leading to this possibility.

This may not really answer your question, but I hope it gives some insight into it. 

Comments

Lee Kun, that actually makes sense. Thank you for the insight. I just found it odd that certain areas allowed this to happen while others did not. I am just surprised that CIP left the tiles that way.