Re: Sorting bounding boxes back to front

"Ron AF Greve" <ron@[EMAIL PROTECTED]
> wrote in message 
news:472a6ef0$0$233$e4fe514c@[EMAIL PROTECTED]
> Hi,
>
> I have been developing my game engine for a few years now and the last
few 
> months decided to go from a 2D engine to a 2.5D one (actually 3D but I 
> think I leave the camera at fixed points so I can mix 2D and 3D 
> together).I can currently ex****t meshes and bone animations (a single 
> vertice can be affected by different bones) as wel as pure object 
> animations (just moving the object itself) from blender and display it
in 
> my engine.
>
> Now I just render anything and let the z-buffer do the work (ok not very

> optimal yet :-)  ). However I also would like to render animations of 
> glass objects so I should be able to sort them back to front in
realtime.
>
> Now for the question:
> Assuming a bounding box that never intersects does anyone know of a good

> algorithm to sort the transparent objects back to forth?
>
> I was thinking of first calculating the projection of bounding box1 and 
> box2 to see if they overlap then if they do shoot a ray through all the
16 
> vertices to see if they hit one of the planes of the other (projected) 
> box. (One of the boxes might be smaller then the other one so I figure
you 
> need to do it for both boxes),
> If they do I could see which one further away by calculating the 
> intersection of the ray and the vertice and the ray and the plane of the

> other box. but it seems like a lot of calculations so maybe anyone knows

> of a smarter algorithm?

If you have the bounding boxes for all the objects, you simply have to
sort 
on the smallest z of each bounding box (closest forward to the camera). 
This shouldn't be a much of a problem at all and should be fairly math
easy.