Author Topic: Twist Scroller - old Amiga effect  (Read 3067 times)

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Offline xen

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Twist Scroller - old Amiga effect
« on: September 13, 2011 »
Remember the classic Amiga demo Hardwired by Crionics+Silents? Remember that awesome looking twist scroller?

I've always wondered how they did it. Was it some vector font deformed as i.e. rubber vectors?
Was it a form of classic vertical twister bar with font bitmap used as some sort of masking?

Any ideas of how that effect was achieved?


Offline Hotshot

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Re: Twist Scroller - old Amiga effect
« Reply #1 on: September 13, 2011 »
Welcome to the forum :)

I dont know what your programming language do you used but it would be interesting to know :)

Twist Scroller? I have seen some...

I am sure there will be DBF Peoples answer your questions :)

Offline jace_stknights

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Re: Twist Scroller - old Amiga effect
« Reply #2 on: September 14, 2011 »
This effect is quite simple: for each font you got an animation -> a simple x-axis rotation.
All font are stored in memory like this:
font 1, angle 0
font 1, angle 1
...
font1, angle 180 (this effect is just making a 180 turn)
font2, angle 0
font2, angle 1
...
and so on for all the fonts.

Then you have a sine wave for the whole scrolltext x axxis. And depending the value, you take the line of the font rotated associated to the scrolltext line position.  (the value give the x-axis, and the angle)

This effet can be done even on Atari ST with pure 68k! Precalculating is good for you!!!

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Offline xen

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Re: Twist Scroller - old Amiga effect
« Reply #3 on: September 14, 2011 »
@Hotshot:
Thanx!  :)
I've used 6510 and 680x0 ASM many years ago. Then switched to C/C++, and lately doing some AS3 (flash), mainly for the purposes of recreating old C64 intros (like this one). But I guess language is not as important as is the logic behind it. :)

@jace_stknights:
Thank you for your answer. Yes, that was one of the ideas I had, but figured it would be a bit complicated and tiresome rendering precalc font 180x for each char and would end up eating too much space anyway, but that certainly is one of the ways of doing it. Some time ago I tried scanning through RAM while running Hardwired to see any gfx data resembling rotated chars (that would suggest precaclulating this), but found only 2d font and some parts of the twist effect without chars applied to them. This is how I figured it must be some other trick they must have used. But never tried looking for and disassembling the actual code as I suck at MC68k ML.

Anyways, thanx for your answer.

Offline jace_stknights

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Re: Twist Scroller - old Amiga effect
« Reply #4 on: September 14, 2011 »
The fonts are color filled on-the-fly with a copper list (on Atari ST it would be rasters) for the light source effect. So the fonts sould be 2 bitplanes!
But I gave you the technique I would have used first ;D
Perhaps they used generated code (I would have done it if this taked too much cpu to copy from memory the precalc font). That's mean instead of storing fonts datas, you have to store routs including the data inside the move.l. That's mean a lot of routs at the end, but more faster!
That why you have to make a routine that generate the code in memory for each case of line, of font, of angle! :o
And perhaps also why you don't find anything in memory with a ripper!  :P
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Offline maracuja

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Re: Twist Scroller - old Amiga effect
« Reply #5 on: September 15, 2011 »
Thanks you Jace !!  :stirrer: :|| :carrot:  :clap:

Offline jace_stknights

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Re: Twist Scroller - old Amiga effect
« Reply #6 on: September 16, 2011 »
Heyyyyy ZE scouic, what about dis remake???  :bfuck2:
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Offline dimmat

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Re: Twist Scroller - old Amiga effect
« Reply #7 on: July 27, 2017 »
Twist Scroller is one of my favourite effects from Hardwired demo. I've made something similar using Scratch:

https://scratch.mit.edu/projects/173280022

« Last Edit: September 06, 2017 by dimmat »