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Buck Rogers - Planet of Zoom - z-index/layering has been broken for a while
#395133 - 11/11/22 03:52 AM
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I'm comparing Sega arcade games to their PC ports on YouTube, and am soon going to get to Buck Rogers - Planet of Zoom.
However, I've noticed that the z-index (or layering, or whatever it would have been referred to in 1982!) is a bit broken. I can't see any bugs in MAME Testers against turbo.cpp relating to this, and there are no MAME alerts of inaccurate graphics before the game begins.
These are the issues I noticed:
1. End of each stage: your ship disappears behind the growing blue warp effect.
2. Round 1 Sector 7 - enemy ships are drawn behind the distant mountains.
3. Round 1 Sector 8 - your ship appears ahead of the mothership, instead of behind it, making targeting it difficult!
There aren't many references of the real arcade out there, but I have found one where the blue warp effect clearly shows the ship in front of the blue area.
Compare this footage of the arcade (all 3 issues above are visible): https://www.youtube.com/watch?v=T-SrMyjljSM
to this of the real cabinet (only the blue warp is visible in this clip, but I suspect the same layering issue affects the mothership fight too): https://www.youtube.com/watch?v=6coJ4_xFvxY
I was wondering if this is a new bug, or whether it's always been like this in MAME, before I capture footage of the arcade version. UPDATE: see below, older versions have correct layering (though other bugs most likely!).
Edited by VirtuaIceMan (11/11/22 02:27 PM)
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Re: Buck Rogers - Planet of Zoom - more findings
[Re: VirtuaIceMan]
#395135 - 11/11/22 02:21 PM
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I've found some videos of earlier MAME versions where the layering appears correct.
This one, using "MAME58" they claim: https://www.youtube.com/watch?v=uur-fwiZJXE
And this one, using WolfMAME 0.106: https://www.youtube.com/watch?v=Jh7zi87YxXk
Plus the arcade version shown here (not sure what MAME version): https://www.youtube.com/watch?v=BrdgchPC83k
Looking at Info of the game and assuming baseline MAME 0.106 was fine, there were changes like these, that seem to relate to the graphics side, perhaps:
0.108u2: Added proms ($0, 20, 100, 300 - Char layer X shift, sprite state machine, sprite Y scaling and video timing). Changed palettesize to 1024 colors.
0.120u1: Couriersud fixed broken starfield in Buck Rogers.
0.129u3: Couriersud and Guru added calculation for capacitors >= 100pf to Buck Rogers LS626 frequency calculation. Formula was derived from figure 6 of LS624/628/629 & 625/626/627 datasheet. The "BUCK ROGERS" title screen is now centered and the big ship appears centered over Buck Rogers ship.
0.130: Aaron Giles fixed graphics corruption on Buck Rogers title screen / ingame (using -autoframeskip).
Edited by VirtuaIceMan (11/11/22 02:27 PM)
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Re: Buck Rogers - Planet of Zoom - the bug has been present since 0.109!
[Re: VirtuaIceMan]
#395144 - 11/13/22 07:43 PM
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Nailed it down to this update breaking the layering:
0.108u2: Added proms ($0, 20, 100, 300 - Char layer X shift, sprite state machine, sprite Y scaling and video timing). Changed palettesize to 1024 colors.
0.109 and newer, your ship now goes behind the blue warp at the end of each sector.
Also, at some point in MAME development, it looks like the colours were changed on sprites. The barriers across the trench in sector 5 have heavy amounts of magenta in them, which the earlier versions of MAME shown above do not. I'm not sure which is correct, as I don't have footage of either running on an arcade cabinet, but the strong magenta looks a bit out-of-place compared to light blue that earlier versions of MAME had.
Edited by VirtuaIceMan (11/13/22 07:45 PM)
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| kmg |
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Your Humble Servant
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Re: Buck Rogers - Planet of Zoom - the bug has been present since 0.109!
[Re: VirtuaIceMan]
#395147 - 11/14/22 10:36 AM
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Thanks for digging into it more. I posted the sprite priority bug issue to mametesters.org a couple days ago. I suspected 0.108u2 would be the breakage as there was a significant overhaul of the video code then and that was the last major change (your notes helped narrow it down quick), but I couldn't test that far back. Can't say about the color differences. Anyway, there's a bug report and a link to the breaking commit on MT.
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Re: Buck Rogers - Planet of Zoom - the bug has been present since 0.109!
[Re: kmg]
#395148 - 11/14/22 01:30 PM
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And thanks for adding it, I was thinking of signing up for MAME Testers otherwise 
Not sure how to validate the colours though; the barriers being light blue and now magenta is a big shift, but they're late in the game, and that only live footage doesn't show much of the game.
The stages with asteroids I think the asteroids look a little more garish in later versions, but again, it's hard to tell without taking lots of comparison screenshots.
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Re: Buck Rogers - Planet of Zoom - the bug has been present since 0.109!
[Re: VirtuaIceMan]
#395255 - 12/03/22 04:47 AM
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I guess it's now a waiting game, to see if anyone picks this bug up.
It's listed as minor graphical issue, but it's quite hard to shoot the mothership, when your jet is drawn in front of it, instead of behind!
I'll have to go back to MAME 0.108 when I make a YouTube video about the game, I guess.
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| kmg |
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Your Humble Servant
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Reged: 04/12/21
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Posts: 19
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Re: Buck Rogers - Planet of Zoom - the bug has been present since 0.109!
[Re: VirtuaIceMan]
#395256 - 12/03/22 08:23 AM
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I bumped it up to major graphical issue. Yeah, the mothership battle is more than just a cosmetic annoyance.
The good news is that priorities worked in the old version and there are even schematics for this board in the couple hundred page operator's manual. The rewrite in 0.108u2 looks to be based on the schematic, and maybe the older version was based on debugging and guesswork? Unfortunately it will take a patient person comparing the two versions and/or checking against the schematics, so it may be a long wait.
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Re: Buck Rogers - Planet of Zoom - z-index/layering has been broken for a while
[Re: VirtuaIceMan]
#395262 - 12/03/22 03:11 PM
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> Compare this footage of the arcade (all 3 issues above are visible):
> https://www.youtube.com/watch?v=T-SrMyjljSM
>
> to this of the real cabinet (only the blue warp is visible in this clip, but I
> suspect the same layering issue affects the mothership fight too):
> https://www.youtube.com/watch?v=6coJ4_xFvxY
In case anybody else is looking into this issue, and doesn't want to have to sift through over half an hour of shaky-cam footage with a bunch of people spending over half the video not actually talking about the game the video is titled after, the warp effect appears for about 2 seconds between 4:19 and 4:21 in the second video.
It appears between 1:55 and 1:57 in the first video.
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sound
[Re: MooglyGuy]
#395297 - 12/14/22 01:22 AM
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I think that real cabinet also shows the sample-based audio up, as the engine noise rises and falls as you accelerate and brake, where in MAME it's a constant tone. Not sure if the regular high-pitched beeps are a correct feature of the arcade, or not, but they're quite annoying!
Also: in MAME the gameplay slows down whilst you're firing. Not sure if this is just because the primitive hardware was overwhelmed or not, or an emulation issue (can't tell from that real cabinet, as he keeps on shooting!).
Edited by VirtuaIceMan (12/22/22 02:23 PM)
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Re: Buck Rogers - Planet of Zoom - the bug has been present since 0.109!
[Re: kmg]
#395331 - 12/19/22 01:08 AM
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Looks like on MAMEtesters that hap submitted a fix. If I can get hold of a compiled version I'm happy to test it (but don't have the skills to compile MAME myself).
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Re: Buck Rogers - Planet of Zoom - the bug has been present since 0.109!
[Re: VirtuaIceMan]
#395332 - 12/19/22 09:53 AM
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> Looks like on MAMEtesters that hap submitted a fix. If I can get hold of a compiled
> version I'm happy to test it (but don't have the skills to compile MAME myself).
GitHub Actions is a thing.
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new bugs on new build
[Re: kmg]
#395365 - 12/25/22 02:50 AM
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Just been testing this; the priorities are fine, but if you compare the logo (with green/blue bars behind) on attract mode, it's now a bit narrower than before. Also the blue warps at the end of each level don't entirely cover the screen (transparent strip on the left-hand side of about 2 pixels).
Also, as graphics unload (title screen, when enemies are destroyed, etc) sometimes corrupt images are shown for a frame).
I'm going to use it anyway for my video, but just reporting what I notice!
Edited by VirtuaIceMan (12/25/22 10:43 AM)
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