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Old 20 March 2020, 07:34   #1
dreamkatcha
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Nebulus' 'precise hidden surface removal'

In the manual for the various versions of Nebulus it proudly exclaims the implementation of "Rotational 3D scrolling with precise hidden-surface removal running at 25 frames per second, and multi-layer parallax scrolling on underwater levels at 50 frames per second."

Hidden-surface removal?
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Old 20 March 2020, 08:31   #2
Coagulus
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Im assuming it's when the steps go around the side?
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Old 20 March 2020, 21:34   #3
dreamkatcha
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I dunno. If you remove a hidden surface (even if it's done precisely), how would anyone know anything had changed? It sounds like a running gag from Catch-22 to me. :|
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Old 25 March 2020, 04:54   #4
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It removes the surfaces that won't be seen so they don't have to be drawn, speeding up the process by only drawing (or rendering in the case where there is actually something 3d happening here) what the player can see.
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Old 25 March 2020, 10:26   #5
dreamkatcha
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Ah, now I get it, thanks. So a technically impressive trick used to deliver the rotating tower effect, although something that goes on in the background that wouldn't even occur to the player unless they knew about coding. That's where I was lost - I was expecting to be able to actually see some change or other on screen.
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Old 25 March 2020, 10:40   #6
DanScott
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seems to me it can just be done with a couple of compares.. nothing technically impressive really
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Old 25 March 2020, 15:16   #7
commodorejohn
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They're taking the piss. No way is it actually doing 3D math of any kind, when you can far more easily just draw a 2D representation of brick lines scrolling across a rectangular area and cycle it with the player position.
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Old 25 March 2020, 16:11   #8
roondar
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I always thought it was just a cleverly designed animation. Note that they also have the same game running on much less powerful hardware and it still runs great, which makes me suspect it's animation all the more.

Does anyone know for sure?
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Old 26 March 2020, 03:22   #9
saimon69
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More than animation is z-stacking with double buffering imo
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Old 28 March 2020, 12:21   #10
gimbal
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I ran into this coding secrets video about Mickey Mania which actually has a rotating tower inspired by Nebulus in it. The video shows some of the tricks to get the tower to work, quite interesting.

[ Show youtube player ]
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Old 28 March 2020, 18:50   #11
commodorejohn
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Hah, nice breakdown.
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Old 28 March 2020, 20:52   #12
saimon69
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The mickey mania tower has the addition of angled steps compared to the static blocks of nebulus, though; i suspect the c64 one is even smaller in footprint
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