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Simulation of 3D objects in original Duke Nukem 3D  "2.5D vs 3D"

User is offline   Sat42 

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#1

Hi all,

I wish to know if anyone here could give a final bit of explanation as to how the Build engine - as it was at the time of Duke Nukem 3D's release in 1996 - handled the representation of 3D objects.

I already understood most of the tricks - I found a nice break down of the problem here:
http://infosuite.duk...e=ae_tricks_b7#
so I know how the bridge in the first level of the game is done, and I know about the sloped column, etc.

However, the wall-aligned or floor-aligned 'collapsable' sprite technique has obvious limitations, namely the requirement to be square or rectangular, and the inability to be sloped.

My question arose from observing the rotating 3D lamp in the arcade room of Hollywood Holocaust: it very clearly has sloped faces, and so I figure it could not have been made using the wall-aligned or floor-aligned 'collapsable' sprite technique. I don't see how the sloped column technique would work either. In fact, when I first played the game this kind of object is what made me think that Duke Nukem 3D demonstrated the ability to incorporate 3D polygonal models in an otherwise 2.5D world (other games with 2.5D engines have certainly done this, e.g. Ultima Underworld - which allowed the latter to have bridges where one could go both on top and underneath).

But I can't find any info saying that Duke Nukem 3D used at least some 3D polygonal meshes - it's all about using sprites and slopes to simulate true 3-dimensional objects - but then how is that lamp in the arcade possible? Pretty sure I remember a similarly sloped "3D" object in the Lunar Apocalypse episode but I was unable to check recently.

Hope someone can help me understand this!
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User is online   Trooper Dan 

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#2

The thing you are referring to is not a sprite or a model, it's a rotating sector.
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User is online   necroslut 

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#3

Notice that it's convex and attached cleanly to the ceiling - that's because it is part of the ceiling.

Blue barrels are heavier than regular barrels
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User is offline   Sat42 

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#4

View PostTrooper Dan, on 25 August 2018 - 04:17 PM, said:

The thing you are referring to is not a sprite or a model, it's a rotating sector.



View Postnecroslut, on 25 August 2018 - 05:08 PM, said:

Notice that it's convex and attached cleanly to the ceiling - that's because it is part of the ceiling.



Thank you both for your replies! I am quite impressed by the ingenuity of the technique - as far as the engine is concerned, nothing is proper 3D, but with this and the other tricks mentioned above, what's rendered is effectively 3D and that (together with all the interactivity of course) certainly helped me get immersed in this game to a higher degree than in DOOM.

Cheers!
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