Cats crossed the wall

[Pi78 Allen]

Hi there,

I live on an island with water on all sides. To avoid my cats fall in water, I put a wall (1 prim with hollow) around the parcel. Unfortunately, it's not enough: every week, I find one of my 5 cats in the water, this means they can pass through the wall! I tried to increase the thickness of the wall but no success. Of course, texture change, wood or steel, is not a solution! So, WHAT CAN I DO?

Thanks for any trick and/or explanation

[Tad Carlucci]

Cats have done this since Day One.

This is the same problem as cats falling through floors.

The only solution is to home your cats in the center and set their range so that they cannot TOUCH the wall. (If they DO touch the wall, they can go through it and move OUTSIDE the wall AND the set range.)

Any cats which do get outside the range and wall will, of course, jump home when they go to sleep.

---

Years ago, as a test, I set up the walls so that the cat was forced to move diagonally across an entire sim (over 300 meters away from its home), even though the range was only 10 meters. KittyCatS Resident and I spend several hours working the problem and determined there is really nothing to be done about it without completely redesigning how KittyCatS move and interact with the world.

You can try multiple walls, say 1 meter thick, overlapping with the centers spaced 0.1 meters apart. Those cats which make it through the first wall surface will hit the second; but some till also wiggle through the second. Each layer added reduces the chances of making it through all walls; but there will always remain a chance, no matter how many wall layers you use, that a cat can make it through all of them. In practice, though, two or three walls is good enough.

[Pi78 Allen]

Thanks for your reply.
Shame if I have to set a range because my land is longer than large so it's a waste of space for the cat. I wonder WHY there is a "full parcel" option in the range if it is not reliable...

On the other hand, multiple walls is not THE solution: the cat will escape later, but he will!

If you put an avatar in a prison, he will not escape (well, he can tp or sit on something outside!), why a cat would?

In fact, I think this is a serious bug in the conception of the cat. It would be interesting to have the developer's opinion.

[Tad Carlucci]

The problem is that cats change from physical (when moving) to non-physical (when not moving). So, consider a physical cat sliding along a wall then deciding to stop and becoming non-physical. At this point all is well. But, when it decides to move again, it switches back to physical. If, at this point, the cat is ever-so-slightly past the face of the wall, it is 'inside' the wall, and the wall and cat become 'temporarily non-physical, with respect to each other' .. that is, the wall (from the cat's point-of-view) ceases to exist. This holds until the cat moves 'outside' the wall (in any direction). If the cat is now further from home than the wall, it slides along the outer side of the all .. even if that is beyond the range for the cat .. even if the range is set to Parcel, and the cat is outside the parcel. This can also force the cat off the region, but that opens up a slew of other problems.

The reasoning for switching back and forth between physical and non-physical is to reduce lag. Remember, cats were created long before mesh came along. Back then, setting the cat non-physical removed it from the physics phase (since mesh arrived, it no longer does); thus reducing lag.

Cats were not the only things having problems like this. Pathfinding was introduced as the solution; but is such an abject failure (since it is so rarely properly set up) it really is not an alternative.

So, the choices are:

- Live with the issue, doing what you can to mitigate the problem, such as reducing the range or adding wall and floor prims.

- Remove all movement from cats.

- Have cats always be physical; significantly increasing lag.

Of these, doing nothing is the best choice.

[Pi78 Allen]

Thanks Tad for this great explanation!
Of course, for the users, "doing nothing is the best choice" as you said... and we don't really have another choice
However, for the developers of the cats, there is probably something to do to make them smarter, to be able to detect a fatal collision before it be too late. Here is the solution!

[Tad Carlucci]

As a programmer, yes, I can see ways to handle the problem purely in code. But, if done in scripting, the lag would be horrendous! This is one (of many) problems with Second Life which is best handled by the simulators. Unfortunately, the attempt to do just that, pathfinding, is an abject failure.

[Pi78 Allen]

This is just an idea: if the problem is too complex to solve on the cat, what about a kind of electric fence which pushes the cat each time he is too close of the wall?