33 fps

Got a programming project in mind? Tell everyone about it!
User avatar
Rich Talbot-Watkins
Posts: 1089
Joined: Thu Jan 13, 2005 5:20 pm
Location: Palma, Mallorca

33 fps

Postby Rich Talbot-Watkins » Mon Jun 12, 2017 11:27 am

So, sometimes on the Beeb, particularly in horizontal scrolling games, 50 fps is just too fast, while 25 fps is too slow (and suffers that horrible double image effect). So I was wondering what it looks like if you do alternate 50/25 frames, just to get the speed right - has anyone ever tried it? Chuckie Egg actually runs at this frame rate, but without any attempt to match vsync (hence all the flickering!).

While tidying up my hard drive, I found an old, old project of mine: basically Blurp using line-by-line vertical scrolling, which I started on my old BBC Master (RIP) years ago, and which sorvad kindly rescued from an old 5.25" floppy and made me an ADFS disc image. I didn't pursue it much because 50fps didn't give me a lot of time to update all the enemies required, but also because it just went too quickly. 25fps looks horrible, so I just tried the middle option (as proposed above), and under emulation it works surprisingly well.

Have a look for yourself (there are three disc images in the attached zip). How does the 33fps version look on real hardware? Is the variable frame rate jarring, or does it work OK - and does it look better or worse than the constant 25fps version? Have you ever tried anything like this, tricky?
Attachments
BlurpSmooth.zip
(82.82 KiB) Downloaded 36 times

User avatar
tricky
Posts: 1816
Joined: Tue Jun 21, 2011 8:25 am
Contact:

Re: 33 fps

Postby tricky » Mon Jun 12, 2017 12:59 pm

Not intentionally ;), but I did have this in one game (can't remember which) where I wanted to do a chunk of processing, but waited until the next frame if it was after a certain time. It had scrolling landscape, and didn't look vary good as you were watching what was scrolling on.

I think for Blurp!, it could be OK, as you are looking at the main character and not what is scrolling towards them. 33fps certainly feels like a good speed for the game. I'll give it a try on real hardware at home tonight.

If it means that you will finish the game, I'm sure we would all agree that it is perfect! :lol:

PS I might give it a try on my Rally-X game as I think I am alternating between drawing both sides and drawing one and ANDing the other (which is a little quicker) and slowing it down wouldn't hurt. It may not work as you will again be scrolling the whole time and probably watching what is scrolling on.

User avatar
Rich Talbot-Watkins
Posts: 1089
Joined: Thu Jan 13, 2005 5:20 pm
Location: Palma, Mallorca

Re: 33 fps

Postby Rich Talbot-Watkins » Mon Jun 12, 2017 8:40 pm

I doubt this tech could develop into anything like the software scrolled Blurp, as, however you look at it, there's just not really enough time to plot up to 16 monsters, plus bullets and all the dots in a single frame (and less so in MODE 2 as opposed to MODE 5!).

But I was just pondering whether this works as a way of artifically slowing down a game which can be updated in a frame, or whether it looks horrible. Under an emulator, on my 60Hz monitor, I can't really tell. It was one of the things which stopped me from developing it any further at the time: the fact that 50fps just scrolls too fast horizontally, while 25fps just looks sluggish. Maybe 25fps, in the right game, would still look nice. Exile has moments which continuously scroll at 25fps as you walk sideways, and it looks fine.

User avatar
tricky
Posts: 1816
Joined: Tue Jun 21, 2011 8:25 am
Contact:

Re: 33 fps

Postby tricky » Tue Jun 13, 2017 6:21 am

Unfortunately, I only have LCDs available as all my CRTs are packed away at the moment (sorry, I forgot) so my test may not be valid, but all smoothing is off. It looks OK, a little better than 25, but not as smooth as 50.

I wonder if we are at a point where a modern LED can actually smooth the motion and make 25fps OK for those of us who are more sensitive to it?

I'd forgotten that Blurp! was software scrolled, I would love to see one of your games finished on the beeb/master (I would also love to see me finish Jeltron or even Phoenix :oops: )

I always thought that Rally-X looked quite fast at 2 mode 1 pixels and 50fps, but looking at it from this perspective, I guess it is just that you are being chased and that the arcade version is actually 2@60 (=4@30), so much closer to your 4@33.

PS jsbeeb performance in FireFox (53.0.3 32bit) for Rally-X seems to have tanked (fine in Chrome and I'm not sure why 32bit) http://bbc.godbolt.org/?autoboot&disc=https://dl.dropboxusercontent.com/s/a4ft2b398smj54p/RallyXDemoWipCRTCorBem.ssd
Attachments
RallyXDemoWipCRTCorBem.zip
****** Requires jsbeeb, B-em or a CRT to work properly ******
(5.21 KiB) Downloaded 16 times


Return to “projects”

Who is online

Users browsing this forum: No registered users and 3 guests