[Fixed] DECORATE: SpawnFloat

[Cornflake]

I pretty sure this is a bug:

In the DECORATE lump, there is a flag called SpawnFloat, which is supposed to make a decoration "spawn at a random height between the floor and ceiling".

I put the decorations in my level in a room that had a floor height of 0 and ceiling height of 384, but the decorations only seemed to spawn at most 128 units above the floor. I tried giving them an initial height but that seemed to do nothing.

The only flags I had set were NoGravity and SpawnFloatin the DECORATE lump.

Here comes the strange part:

I made the ceiling 512 instead of the 256 and the maximum height of the decorations semed to jump to about 144 units above the floor. I raised it to 4096 and it seemed to jump to 192 or so. A ceiling with a 64 unit height made the decorations sit flat on the floor.

Is there something messed up with calculating the heights of decorations using SpawnFloat? It seems as if the differences are exponential.

[Graf Zahl]

That's the calculations that are done:

Code: Select all

	else if (iz == FLOATRANDZ)
	{
		fixed_t space = actor->ceilingz - actor->height - actor->floorz;
		if (space > 48*FRACUNIT)
		{
			space -= 40*FRACUNIT;
			actor->z = ((space * rng())>>8) + actor->floorz + 40*FRACUNIT;
		}
		else
		{
			actor->z = actor->floorz;
		}
	}

They perfectly match your results and they are exactly the same in Hexen and Heretic where this flag comes from.

[Cornflake]

Well, then this page should be changed to reflect what it truely does:

http://www.zdoom.org/wiki/wiki.phtml?title=DECORATE

The part where is states: "spawn at a random height between the floor and ceiling" is misleading.

[NiGHTMARE]

Why not change it yourself? That is the whole point of a Wiki afterall

[randi]

Except you got the wiki entry wrong. The correct behavior is:

• Is the space at least 48 units tall?
  • No, then spawn it on the floor.
  • Yes, then spawn it at least 40 units above the floor.

It behaves strangely because this bit overflows when the space is more than 257 units (after subtracting 40):

Code: Select all

(space * rng())>>8

Simple to fix:

Code: Select all

MulScale8 (space, rng())

[Graf Zahl]

So this was a bug that has been in Heretic and Hexen, right?

[randi]

Yes.