BBC Micro and Acorn Electron demo effects

[SimonSideburns]

Strange.

I can see the one mimicking ZX Spectrum loading bars, but the rest come up as:

The video does not exist.

I'm in the UK too.

[oss003]

Strange.

I can see the one mimicking ZX Spectrum loading bars, but the rest come up as:

The video does not exist.

I'm in the UK too.

I knew it .... I'm not the only one living in China ......

Greetings
Kees

[0xC0DE]

I'm sorry guys. I really don't know how this happens or if there is anything I can do to fix it. The videos are definitely Public. It seems that most people can watch my YouTube videos but some can't. Does anyone know how to fix this?

[oss003]

Hmmm .... looks like a Google Chrome problem.
The video's are working in Firefox.

Simon, are you also using Google Chrome?

Greetings
Kees

[Multiwizard]

Hi,

I'm still using WinXP Professional SP3

Here all the video's are working on Firefox and Chrome...


Greetings, Wim...

[roland]

Real time ZX Spectrum-like loading (and saving) screen for the Acorn Electron anyone?
Watch my Speccy loader while loading and saving a program on my actual Electron

Funny, we're working hard on our Atoms to get rid of the screen noise and you introduce it on the Electron

Your demo's look great. Is there any chance that you visit our techsat in June?

[0xC0DE]

Your demo's look great. Is there any chance that you visit our techsat in June?

Thanks Roland. I'm sorry but I won't be able to make it to Dutch Techsat in June.

[richardtoohey]

Tried a few of the links (I'm in NZ) and working here on Firefox/Chrome (well, Chromium).

I'm not logged into Google/YouTube (if that makes any difference?)

[SimonSideburns]

I am indeed using Chrome, but I can try from my smart TV which has a Youtube app built in, and will let you know the outcome.

[0xC0DE]

Another classic demo effect: smooth text scrolling.
This one took a while to get just right and uses every available cycle on an Electron.

MODE 1. 50 fps at all times. Optional color cycling. Super smooth text scrolling at 1 pixel per frame.
Works best (and 100% smooth) on a real Electron. Second best is ElectrEm.

Watch the video here: https://www.youtube.com/watch?v=K31qdXX6F0Y

Or even better: try it on your own Acorn Electron.
Be patient when loading, especially from tape. The screen will be black during loading.

Tape image:

scroller.uef

(14.44 KiB) Downloaded 102 times

Disk image:

scroller.ssd

(200 KiB) Downloaded 126 times

Let me know what you think of it. Enjoy!

[0xC0DE]

Can you confirm they are working on MAME? I haven't tested yet.

I wasn't expecting them to look great in MAME but they're not far off. The worst is the plasma with the static acorn, it jumps around a little.

I have just tested the "static acorn" one on MAME (standard Electron) and it looks okay!? I have tested the UEF version by the way. I'm having trouble getting MAME to accept my SSD images (maybe because they are not padded to exactly 200K?). What am I doing differently than you that you get the acorn jumping around?

[Pernod]

I have just tested the "static acorn" one on MAME (standard Electron) and it looks okay!? I have tested the UEF version by the way. I'm having trouble getting MAME to accept my SSD images (maybe because they are not padded to exactly 200K?). What am I doing differently than you that you get the acorn jumping around?

MAME has to analyse the SSD contents to determine the image type, file extensions are irrelevant. One of the checks it performs is that it has a valid number of tracks so the sector count must be divisible by 10. Change bytes at offset &106/107 to &33/20 to make it think it's an 80 track SSD.
I use 'electron -exp plus1 -cart1 peg400' to run SSD's.

The plasma.ssd demo looks great, it's the plasma-no-color-cycling.ssd where the acorn is flickery and moves left/right, likely timing related. It's a MAME issue so hope you don't think you have to fix the demo.

[tricky]

Nice scroll, does it use pre shifted copies of the text, or actually pixel scroll that area? Is it fully unrolled?

[0xC0DE]

Nice scroll, does it use pre shifted copies of the text, or actually pixel scroll that area? Is it fully unrolled?

It's a mix of fast byte (4 pixels) scrolling in partially unrolled loops, palette switching and screen start address switching (to show one of four hidden copies of the bar). And pixel perfect sprite plotting to get the righthand side of the scrolling area updated. The main loop is synchronized to the RTC interrupt. I wanted to get 50 fps in mode 1, so it took some experimenting with getting the right size of the scrolling area. Which is 128 by 24 pixels at the moment.

[billcarr2005]

How simple / difficult would it be to tweak the code to get these demos running OK on the BBC?

[0xC0DE]

How simple / difficult would it be to tweak the code to get these demos running OK on the BBC?

Fairly simple (famous last words!). As you may have noticed I'm a bit of an Electron fanboy though and I love the challenge of getting these demo effects to work on such a humble machine. But you may just have initiated my next little project: getting them to work on a BBC as well. Ideally, one version that works on both.

As I don't have a Beeb myself, what is considered the best, cycle accurate, BBC emulator on Windows?

[tricky]

Excluding b2 because i havent used it much.
B-em is probably most accurate (its only of by a cycyle or two from HW.
Beebem is off by one scan line from vsync and only reads the palette once per line iirc.
Jsbeeb is very good and can be run in a browser from windows

[0xC0DE]

How simple / difficult would it be to tweak the code to get these demos running OK on the BBC?

Fairly simple (famous last words!).

Famous last words indeed. That took more effort than expected. I started with converting the most difficult demo effect: the text scroller.
I have now created a unified demo that works on a BBC Micro and on the Electron.

Here is the disk image (works on Beeb and Elk):

textscroller.ssd

(200 KiB) Downloaded 93 times

And the tape image (works on Beeb and Elk -- be patient while loading):

textscroller.uef

(16.84 KiB) Downloaded 68 times

I don't have a Beeb myself. Can someone please confirm the demo works as expected on a real Beeb? Showing a smooth 50fps scrolling text, without flickering and such. It should look like this:

On the Electron it should look like this:

textscroller - Acorn Electron.png (8.11 KiB) Viewed 7569 times

[tricky]

On the beeb we can cheat when it comes to horizontal pixel scrolling a cut down mode 1

[0xC0DE]

Plasma Eggs demo effect revisited.
Unified demo now runs on BBC and Electron.

plasmeggs.png (23.3 KiB) Viewed 7517 times

Keys:
1 - 50fps
2 - 25fps
3 - 16fps
4 - 12fps
5 - 10fps
SPACE - 'Fire' colour palette
RETURN - 'Ice' colour palette
ESCAPE - quit


Disk image:

plasmeggs.ssd

(200 KiB) Downloaded 95 times

Tape image (be patient while loading):

plasmeggs.uef

(24.6 KiB) Downloaded 80 times

[paradroid90]

Great Stuff, its great to see the Elk getting some love I am also a bit of an Electron fanboy

[0xC0DE]

Thank you very much

[tricky]

I love the effect, but it looks like there is a pixel missing every 32 pixels, as if the pattern was 33 pixels wide but only showing 32 - no gap.
Watch the bits with red lines around them as it animates.

[0xC0DE]

Thanks tricky, and yes, you may be right about that.
I got the idea and the graphics straight from this webpage: http://norecess.cpcscene.net/the-elders-scrollers.html
I will see if I can improve it further.

[tricky]

Its great, but 15 years in the games industry has trained my eye to spot these things - its a pain mostly now

[0xC0DE]

I appreciate your attention to detail. So I have fixed a lot of pixels in the plasma image. And I think it looks better now

plasmeggs.ssd

(200 KiB) Downloaded 112 times

[billcarr2005]

I appreciate your attention to detail. So I have fixed a lot of pixels in the plasma image. And I think it looks better now

[tricky]

That looks great and I love that you are making demos "cross-platform".

[0xC0DE]

Thanks. Also an interesting experience for me as I don't know the Beeb as well as I do the Electron.

[0xC0DE]

0xC0DE presents... Electron/BBC STARFIELD demo - parallax star field with 3 layers

Cross-platform demo that works on Acorn Electron, BBC Micro or any emulator.

Controls:
< - change direction counter-clockwise
> - change direction clockwise
UP - increase number of stars to maximum of 240
DOWN - decrease number of stars to minimum of 24
RETURN - toggle speed
ESCAPE - pause
SPACE - reset to default

Technical information: 100% 6502 machine code, no MOS, one binary with multiple host support, screen MODE 4, 3 layers of stars with parallax effect, minimum of 24 and maximum of 240 stars in 3 different sizes, different every time, double screen buffer.

YouTube: https://youtu.be/dwPumos6LPo

Disk image:

starfield.ssd

(200 KiB) Downloaded 110 times

Tape image:

starfield.uef

(7.99 KiB) Downloaded 74 times

Enjoy, and please leave a comment.