Scratch

When you say "displayable objects", does that include hidden sprites?  Does the action of Hide/Show change the position in the display list?  In other words, if object B is behind A and A then goes through a Hide/Show cycle, is B still behind A when it reappears?  I can do some experiments to try and figure this out, but if you have already done them or have information from the Scratch team, it could save a lot of time.

I think 2.5D would be a great addition to Scratch.  The current system is quite cumbersome.  At least, it's giving me pains.

Thanks!

Yes, it does get pretty messy.  That is the problem, there is no absolute order.  But now that I've got a slightly better idea of what is happening, maybe I can come up with something workable.

The project I'm working on sounds simple enough:  There is a cat in a field with a large rock.  I want the cat to be able to walk behind the rock when it is at a greater Y value than the base of the rock and in front of the rock when it is at a Y value less than that of the base of the rock.  It gets pretty messy though when you look at oblique traveling paths that intersect with the base of the rock; when traveling from below, you want the rock to stay in the background until the entire cat is over it.  When traveling from above, I want the rock to stay in the foreground until the feet of the cat travel lower than the rock (the cat needs to be able to "hide").  I have a messy algorithm that works fairly well under most conditions now but it does not scale well with additional objects in the space and I feel there should be a cleaner solution.

Last edited by Paddle2See (2008-01-07 03:34:13)

That seems very reasonable to me.  Leaving the "z" out of the description and just calling the new value "layer number" would probably clear the confusion up (z seemed to get people thinking of 3d).

Some layer list must already exist within Scratch, so it seems like the implementation wouldn't be too hard.  I haven't bothered much with this recently, but it seemed to me that what must be going on is something like:

Each new sprite adds an unseen "layer" to the project (perhaps each new sprite goes to the "most" distant layer?).  So Sprite 1 is on layer zero (front), Sprite2 is on layer 1, etc. 

Telling Sprite3 to go to the front would bump S1 and S2 back. 

Telling Sprite3 to go back one layer would put it between S1 and S2 (maybe?).  This gets really messy when a lot of sprites are involved and you want to control who is in front of who.