Re: [Algorithms] Depth-Sorting Axis-Aligned Boxes

[metanet s. <met...@ya...>]

> > The picture you included in a subsequent post HAD the
> > boxes overlapping.
> 
> Sorry, I meant that in 3D the boxes wouldn't be
> interpenetrating, they would be separated or resting on each
> other; when projected onto the viewing plane they will
> almost definitely overlap -- hence the need to sort them
> somehow.

I just realized you must have been referring to how the blue box was within the extents of the red shape; in this case the red shape would be modeled as three boxes (top and sides are all separate AABBs of minimum thickness).





--- On Mon, 8/3/09, metanet software <met...@ya...> wrote:

> From: metanet software <met...@ya...>
> Subject: Re: [Algorithms] Depth-Sorting Axis-Aligned Boxes
> To: "Game Development Algorithms" <gda...@li...>
> Received: Monday, August 3, 2009, 3:15 PM
> 
> > The picture you included in a subsequent post HAD the
> > boxes overlapping.
> 
> Sorry, I meant that in 3D the boxes wouldn't be
> interpenetrating, they would be separated or resting on each
> other; when projected onto the viewing plane they will
> almost definitely overlap -- hence the need to sort them
> somehow.
> 
> 
> > Building a BSP tree makes sense for static geometry
> but
> > perhaps
> > less for dynamic geometry (though you could merge
> dynamic
> > objects
> > into a prebuilt static tree).
> 
> I figured that a combination of using sweep-and-prune for
> broadphase collision detection, and the fact that all of the
> polygons are parallel to world planes (xy,xz, or yz),
> building a BSP would be simplified: we'd already have all
> the faces sorted in order along each axis, as well as
> knowing which pairs overlapped along which axes. 
> 
> Possibly "kd-tree" is a better description, since all the
> planes would be axis-aligned.
> 
> So far my fall-back plan is to use a head-on perspective as
> in SNES Zelda; this avoids the cyclical
> three-mutually-overlapping-faces problem. Sadly it doesn't
> really look or work as well when you're trying to depict
> depth :(
> 
> thanks again,
> raigan
> 
> 
> 
> 
> 
> --- On Mon, 8/3/09, chr...@pl...
> <chr...@pl...>
> wrote:
> 
> > From: chr...@pl...
> <chr...@pl...>
> > Subject: Re: [Algorithms] Depth-Sorting Axis-Aligned
> Boxes
> > To: ra...@ha...,
> "Game Development Algorithms" <gda...@li...>
> > Received: Monday, August 3, 2009, 2:14 PM
> > 
> > Raigan wrote:
> > > Sadly I don't have a z-buffer, so I need to
> determine
> > a way to sort
> > > the boxes back-to-front. The boxes will all be
> > non-overlapping,
> > > although they may be touching, and will move
> smoothly
> > (i.e not by
> > > grid-sized steps as is common in some games).
> > 
> > The picture you included in a subsequent post HAD the
> > boxes
> > overlapping.
> > 
> > 
> > > Is there a simple solution to this problem? I.e
> a
> > formula which
> > > considers the extents and/or a reference point on
> each
> > box to
> > > produce a back-to-front order? Or am I stuck with
> the
> > general
> > > solution: build a BSP tree?
> > 
> > Building a BSP tree makes sense for static geometry
> but
> > perhaps
> > less for dynamic geometry (though you could merge
> dynamic
> > objects
> > into a prebuilt static tree).
> > 
> > There's also Newell-Newell-Sancha:
> > 
> > http://en.wikipedia.org/wiki/Newell%27s_algorithm
> > 
> > which, from the limited description you gave, sounds
> like
> > a
> > better option for you.
> > 
> > 
> > Christer Ericson, Director of Tools and Technology
> > Sony Computer Entertainment, Santa Monica
> > 
> > 
> >
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