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Two of my game projects for the Thomson machines
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Auteur:  Prehisto [ 16 Juin 2018, 15:53 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Amazing! My guess is that you don't move the whole screen but only the displayed elements already shifted in memory (try-to-know-how-i-have-done-that time :))...

Auteur:  W_oo_d [ 16 Juin 2018, 16:19 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Prehisto a écrit:
Amazing! My guess is that you don't move the whole screen but only the displayed elements already shifted in memory (try-to-know-how-i-have-done-that time :))...


Yes the trick is pre-shifting :)

I have another way of doing scroll but it can only go at one speed while the above can have any speed we want.

BTW Prehisto thank you so much for all the invaluable info on the hardware and 6809 you gave me years ago when I first found out about these interesting machines. :)

Auteur:  Samuel Devulder [ 16 Juin 2018, 18:21 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Pre-shifting is one thing, but there is still the clipping to do for elements near the edges of the playfield. That also costs CPU. Or did you also have pre-clipped elements as well ?

Auteur:  Prehisto [ 16 Juin 2018, 19:01 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

I think he has. The screen resolution is bitmap16, so all the shifted combinations don't take too much place in memory, because two shifted positions each (remember a bitmap16 point is 4 bits long) are enough to display everything.

Auteur:  W_oo_d [ 16 Juin 2018, 20:45 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

I am preparing another version of the scroll engine, I will post here a video when it is done and then you will confirm or not if you are correct :)

Auteur:  W_oo_d [ 24 Juin 2018, 11:12 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

I am a bit delayed with the other version because of real life intrusion so I will tell you how I did the scroll.

The scroll area is 28 bytes x 128 lines = 3584 bytes, in a ram bank we have 16384 bytes so we can fit a map of roughly 4 screens * 3584 bytes = 14336, the map can have three configurations:

- 1234

-
12
34 (as in the demo)

-
1
2
3
4


As you can see we can still make the scrolling area a lbit bigger as we have 2048 bytes free in a bank, which gives 512 bytes to use to increase the scroll area to 146 lines but then I can't guarantee if the copying routine will be able to handle it in one frame as I haven't tested it.

Then I pre-shift the bank three times into 3 other banks, so the total is 4 * 16k = 64k. Why four times? because we have 4 pixels in a byte as I am using a non standard screen mode, the 160x200x4, at the moment this only works on MESS and the real machine :)

Then I use a double buffer and with the stack I copy from each ram bank to the hidden screen as the scroll offset requires.

My other version will use the mode 160x200x16 two layers where I will use the technique above for the scrolling background (4 colours) and then I will use the other layer for sprites I can use 4 other colours if the sprites don't overlap the background or the same 4 colours of the background if they do overlap the background. The game will be at 25hz as I need the second frame to draw sprites but it won't be too costly as I don't need to restore the background I just need to delete the sprites which is a bit faster.

Another thing that we can do is to pre-shift the screen into 7 banks, and we can scroll the screen per byte in hires 2 colours at 50hz. This would be cool to show a picture, if I have time I will try to do this demo too.

PS: I have also studied another option to do scroll where it can scroll huge maps but at a fixed speed of 1 pixel per byte and no more whereas the method above allows for several speeds and perhaps we can find a way to increase the size of the maps?!

Auteur:  Prehisto [ 07 Juil 2018, 10:05 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

It's like you took us by surprise, don't you, W_oo_d ? :lol:
Of course, a 160x200x4 screen... So a screen has only 8k data? It's indeed faster to fill up.

Auteur:  W_oo_d [ 07 Juil 2018, 19:04 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Prehisto a écrit:
It's like you took us by surprise, don't you, W_oo_d ? :lol:
Of course, a 160x200x4 screen... So a screen has only 8k data? It's indeed faster to fill up.

:cool: :lol:

Auteur:  W_oo_d [ 11 Avr 2019, 15:40 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Amazing how time passes by...

Finally I have had some time and I am working on a game for the Thomson TO8, with vertical scroll. It is running at 25 fps and it goes much smoother on the real machine than on this video but you can have an idea of how it is looking.
phpBB [video]

Auteur:  Samuel Devulder [ 11 Avr 2019, 15:45 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Damn, that's look promissing! I hope you could finish the game and let us enjoy it :bien: :jap:

Auteur:  Prehisto [ 11 Avr 2019, 15:56 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

:eek: :good:
With sound?

Auteur:  W_oo_d [ 11 Avr 2019, 16:05 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Thank you Sam and Prehisto.

I have not thought of sound and music yet, and I am dreading it because I am null at it specially regarding a computer with just a DAC. I will need help.

I am focused on finishing this.

Auteur:  W_oo_d [ 11 Avr 2019, 21:31 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

I have updated the youtube video as the previous one had very little quality.

Auteur:  Fool-DupleX [ 15 Avr 2019, 13:25 ]
Sujet du message:  Re: Two of my game projects for the Thomson machines

Wow, mindboggling !!! :tourne:

With Mission Lift Off and now that, it shows that the machine actually missed its career by a big chunk ... Imagine if we had that back in the days ...

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