Shadow Of The Beast Parallax Demo STOS

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Shadow Of The Beast Parallax Demo STOS

Postby EstTeeEfEm » Thu Mar 10, 2016 12:57 am

Ok, so I was wondering whether decent parallax scrolling could be achieved using STOS.

Found myself with some clouds from shadow of the beast and the whole thing seemed to take off from there ;)

Included in the MSA disk is the "full" source, there are no corresponding files though because all my datafiles collectively use about 10mb.

Its not particularly fast, nor are the PALSPLIT commands very well implemented. If i chose to do the whole thing in just 16 colours it would be a lot less colourful but more stable. It would also require a complete overhaul of the graphics and rebuilding of the BANK files. There is scope built into it for sprites and more such stuff but mainly this is a technical demonstration of the power of the WORLD command.

It requires 2Mb of mem and even then probably requires a clean boot.
No idea whether it works on a TT or a falcon, but my guess is Aabron (The main sprite) would run too fast for it...

Enjoy, and as a further note... runs far smoother than the original game did, although im lacking the game logic that would also slow things down. If anyone is interested in the whole package of datafiles, test files and source just let me know.

This runs on an STFM too.. as you can see from the source, no wierd ASM calls trickery and no playing with bitplanes.

SOTBSTOS.MSA
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Re: Shadow Of The Beast Parallax Demo STOS

Postby exxos » Thu Mar 10, 2016 10:33 am

EstTeeEfEm wrote:Ok, so I was wondering whether decent parallax scrolling could be achieved using STOS.



Pretty awesome :cheers:
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Re: Shadow Of The Beast Parallax Demo STOS

Postby Ragstaff » Thu Mar 10, 2016 12:05 pm

Nice work. Let this add to the furious debates about whether the ST conversion of SOTB was lame or not ;-)


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Re: Shadow Of The Beast Parallax Demo STOS

Postby EstTeeEfEm » Thu Mar 10, 2016 12:42 pm

lol, a debate about whether or not the ST version was lame ... it was, in my opinion, built for a 512k ST .. If we look at it from that point of view then its certainly not a terrible game. Could it be done faster? or with better quality? i think so but not for a 512k machine. I understand the technical aspects of getting it into 512 and mine would look just as poor as the original game, if not WORSE! if I had tried to squeeze it into 512k. Sure there are demo's out there that show the scrolling can be done in 512 but not the sprites and everything else. It was a trade-off.. less quality for a 512 game. Looking BACK its pretty naff, but in 1989 i dont think a 512k ST could compete with an A500. To do the same scrolling quality on an ST requires much more memory (this STOS one take about 1.8mb but the code is merely 3k). It could be done NOW because we're not constrained by game design politics or business vs pleasure. Someone SHOULD do a better version, and certainly not in STOS lol ;)

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Re: Shadow Of The Beast Parallax Demo STOS

Postby joefish » Thu Mar 10, 2016 10:47 pm

The biggest mistake with SotB and SotB II was to attempt to re-use the Amiga graphics exactly as they were. If they'd been redrawn in a simpler palette the layers could have been scrolled on separate bitplanes just like the Amiga version. Do the foreground in 3 colours + transparent, and the background in just 3 colours (not 4), set the combined overlapping colours to prioritise the foreground, and that still leaves you with 4 colours unused that you can allocate to sprites on the fly.

You could even do this in STOS - make it think it's in medium res, but poke the system to put it back in low res, and STOS can then copy alternating slices of the screen which appear as if you're only copying 2 bitplanes at a time.

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Re: Shadow Of The Beast Parallax Demo STOS

Postby EstTeeEfEm » Fri Mar 11, 2016 5:41 am

STOS can then copy alternating slices of the screen which appear as if you're only copying 2 bitplanes at a time.


You can actually copy 1 2 3 or 4 bitplanes in STOS without messing about with the res. I chose NOT to use this technique because it severely hampers the palette (one of the original sotb issues). There is no transparency on this demo whatsoever, no masking just the shifting required to move by 1 pixel. All of the 16 X n (N = y lines, not all 16 are used) blocks used DO actually overlap and its the way the mapping system works in the missing link.
You'd have to rewrite the extension to allow for transparency in this case. Or use an assembly routine which i've never been a big fan of tbh.

lol, you think the logical screen in the screen Flip is being cleared? :P ;) tricks of the trade :)

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Re: Shadow Of The Beast Parallax Demo STOS

Postby AtariZoll » Fri Mar 11, 2016 7:58 am

joefish wrote:The biggest mistake with SotB and SotB II was to attempt to re-use the Amiga graphics exactly as they were. If they'd been redrawn in a simpler palette the layers could have been scrolled on separate bitplanes just like the Amiga version. Do the foreground in 3 colours + transparent, and the background in just 3 colours (not 4), set the combined overlapping colours to prioritise the foreground, and that still leaves you with 4 colours unused that you can allocate to sprites on the fly.

You could even do this in STOS - make it think it's in medium res, but poke the system to put it back in low res, and STOS can then copy alternating slices of the screen which appear as if you're only copying 2 bitplanes at a time.


With 3 colors for background it would look just awful. Allocating colors for the sprites on the fly ? Only if sprites are in different vertical positions, but when they are in same hor. line - that would eat huge part of CPU time, and actually is not possible when sprites are very close.
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Re: Shadow Of The Beast Parallax Demo STOS

Postby joefish » Fri Mar 11, 2016 9:14 am

How many colours does it need to draw some rocks? Or clouds? You can switch the colours used for the background between rows. The original SotB uses 3-colour sprites and palette splits all over. It worked so well on the Amiga as the graphics were drawn in 8 colours to display on separate layers of 3 bitplanes each. The equivalent on the ST is to use two bitplanes for each layer. If you want the speed you have to sacrifice something.

As for STOS, you can do whatever you want if you bung in the right extension! I was using the original language. I started writing 68000 assembly based around copying graphics around between STOS screen banks. Although I confess I never got round to trying things like Missing Link. There'll always be a limit to what you can do at a reasonable frame rate though.

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Re: Shadow Of The Beast Parallax Demo STOS

Postby exxos » Fri Mar 11, 2016 10:03 am

Looks pretty good to me..

SOTBSTOS_001.jpg
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Re: Shadow Of The Beast Parallax Demo STOS

Postby calimero » Fri Mar 11, 2016 1:01 pm

joefish wrote:How many colours does it need to draw some rocks? Or clouds? You can switch the colours used for the background between rows. The original SotB uses 3-colour sprites and palette splits all over. It worked so well on the Amiga as the graphics were drawn in 8 colours to display on separate layers of 3 bitplanes each. The equivalent on the ST is to use two bitplanes for each layer. If you want the speed you have to sacrifice something.

but Amiga have Copper processor for palette switching and on ST you would need sync coding for changing palette on fly!?

beside planes on ST are interleave so I do not see how you can speed up graphics using only e.g. 2 instead of 4 bitplanes?
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Re: Shadow Of The Beast Parallax Demo STOS

Postby exxos » Fri Mar 11, 2016 1:15 pm

IIRC STOS 3D could only use 4 colours out of 16, that used reduced bitplanes to gain some speed.

MISTY has some results on it ..

Code: Select all

COMMAND         TEST            BASIC (VBL)     COMPILED (VBL)
---------------------------------------------------------------
FASTCOPY        50 times        48              46
SCREEN COPY                     54              54
---------------------------------------------------------------
SKOPY 4    100 (160x99 block)   31              27
SCREEN COPY                     41              37
---------------------------------------------------------------
SKOPY 1         "               21              16
SKOPY 2         "               25              21
SKOPY 3         "               39              34
---------------------------------------------------------------




Where SKOPY X is the number of bitplanes.

The ST screen display is made up of four 'BITPLANES' this is rather like having four translucent pieces of plastic in front of each other. The sixteen colours are made by varying combinations of pixels set in each bit-plane for example:-

colour 1 is made by a pixel set in the 1st bitplane
colour 2 by one in the 2nd
colour 3 is made by a combination of 1 & 2
colour 4 is one in the 3rd
colour 5 is one in the 3rd & 1st
colour 6 is one in the 3rd & 2nd
colour 7 is one in the 3rd , 2nd & 1st
colour 8 is one in the 4th

Colours 9 - 15 are the same as 1 - 8 but with plane 4 set.
Obviously colour 0 is the background and has nothing set
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Re: Shadow Of The Beast Parallax Demo STOS

Postby calimero » Fri Mar 11, 2016 1:34 pm

but bitplanes are interleaved so if you want to shift one entire bitplane for one pixel left, you need to modify 32KB of data.
in case of Amiga you would need to modify only 8KB of data since one bitplane is in continues space.

how do you gain speed on ST by using fewer bitplanes? I do not understand this...
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Re: Shadow Of The Beast Parallax Demo STOS

Postby exxos » Fri Mar 11, 2016 1:41 pm

You have to look at it not as a single screen , but 4 layered screens which "on top" of each other. So if you only copy 2 of those screens (2 bitplanes not 4) then your only working with half the screen information so speed in copying goes up. Each bitplane is in effect 32/4 = 8kb. Its why a lot of games like vroom, or similar, only have trees and zooming stuff normally in very few colours, not because there isn't the colours there, but its quicker to copy about. Someone else probably can explain it better than me...

EDIT1:

It's been talked about before in fact http://www.atari-forum.com/viewtopic.php?t=28828#p286456
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Re: Shadow Of The Beast Parallax Demo STOS

Postby joefish » Fri Mar 11, 2016 3:15 pm

calimero wrote:but Amiga have Copper processor for palette switching and on ST you would need sync coding for changing palette on fly!?

Depends what you want to do, though I think we understand different things by 'on the fly'.

First off, the ST has a raster-based interrupt that can be programmed to occur after a variable number of lines of the screen, and can be used to change palette settings. It's obviously not as versatile as a Copper list, and the main processor has to wait while the interrupt routine runs, but you can do semi-clever stuff like changing the background colour every 8 pixel rows for a pretty sky, then check one of the unused bits in the colour you've just copied, and if it's set, do a more significant palette swap on that particular row. That way it's sort of programmable. At least, that's from assembly. Not sure what STOS extensions there are to implement it.

What I really meant by 'on the fly' is if there are four colours that aren't going to appear on the background or foreground (or arise from a background colour in one bitplane merging with a foreground colour on another bitplane) then you're free to set them to whatever you need for sprites, and if you reserve a few just for enemy sprites, then you can re-allocate them depending on which enemy is about to appear. Leander does this a lot, and just occasionally glitches as you see an enemy change colour just as it leaves the screen and a different object scrolls into view. I didn't necessarily mean change them for different rows of the screen.

The ST has one advantage over the Amiga though - you can end up with any colour as your background - it doesn't have to be 0. So you don't have to mess around trying to stop your colour bars extending into the border like a lot of Copper lists have to.

calimero wrote:beside planes on ST are interleave so I do not see how you can speed up graphics using only e.g. 2 instead of 4 bitplanes?

The bitplanes are still held in separate 16-bit words, though the words are then interleaved. Let's say you have a background and a foreground screen to copy from, each with two bitplanes. You copy two words from the foregrround source, then two words from the background source, then two more from the foreground, and two more from the background. Put together, they give you one 4-bitplane screen sourced from two 2-bitplane screens.

You simply change the address you start to copy from to shift either layer left or right by 16 pixels. If you're clever, you have a bit of self-modifying code in your line-copy routine to make it wrap-around at just the right moment. And for a finer scroll, you need to store the layers pre-shifted in 1,2, 4 or 8 pixel steps.

That's if you're using a buffered scroll. If you're re-drawing the entire screen from tiles then you need a different approach. But you can still just write to every fourth word to address one bitplane.

If you don't use bitplanes, then you have to mask off and merge everything that might pass in front of anything else. You end up treating the whole foreground scenic layer as one huge software sprite, which has to be AND-ed and then OR-ed into the four bitplanes. That slows your game down. But at least you can use all 16 colours.

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Re: Shadow Of The Beast Parallax Demo STOS

Postby EstTeeEfEm » Fri Mar 11, 2016 3:28 pm

Not to start another debate on this but..

As for STOS, you can do whatever you want if you bung in the right extension!


I'll agree with this to a certain extent. Yes, you can do whatever you want, but not specifically at the speed you want. Every extension has been built with the generic requirements making the extension more flexible but less powerful. plus, when compiling, it ALSO uses generic expressions rather than specific expressions to the tasks code.
STOS and indeed any other BASIC derivative will invariably use generic components in its compilation of programs... these are the sacrifices made.

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Re: Shadow Of The Beast Parallax Demo STOS

Postby AtariZoll » Fri Mar 11, 2016 3:51 pm

Yes, you can gain speed by using only 2 bitplanes - as it is in ST version of Uridium. Scroll in game is actually not scroll - it just redraws background from scratch, to say so. Uridium uses 8-bit blits to screen buffer, what self is bad idea because lower speed, so with 4 bit planes it would be too slow. Better code would use more RAM for preshifts and 16/32-bit transfers.
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Re: Shadow Of The Beast Parallax Demo STOS

Postby EstTeeEfEm » Fri Mar 11, 2016 3:57 pm

Better code would use more RAM for preshifts and 16/32-bit transfers.


This is the route I took, although the preshifts are not built in ram but rather as graphics that are loaded, same memory requirements, just leads to bigger files .. no differences other than waiting for ST to preshift in memory.

as it is in ST version of Uridium

I kid you not, this game is sooo slow i almost started to write my own updated version. if the tiles weren't 8x8 it would be a lot easier :P

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Re: Shadow Of The Beast Parallax Demo STOS

Postby exxos » Fri Mar 11, 2016 4:23 pm

EstTeeEfEm wrote:This is the route I took, although the preshifts are not built in ram but rather as graphics that are loaded, same memory requirements, just leads to bigger files .. no differences other than waiting for ST to preshift in memory.


pre-shifting graphics (larger files) is a lot faster than doing them "on the fly" (if thats what you meant ?). I actually requested a pixel perfect screen copy for the extra extension years ago, takes a huge amount of time to shift a image a few pixels. Its one reason why the sprite routines are pretty dreadful because of all the calcs involved. Bobs are better as you can pre-shift the images, so no calculations required while running the game. Its pretty much just copying blocks of data about. Of course takes a lot more RAM as you have to hold up to 16 pre-shifted versions of each sprite. Though generally every 2pixels is fine anyway.
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Re: Shadow Of The Beast Parallax Demo STOS

Postby calimero » Sun Mar 13, 2016 7:14 am

joefish wrote:What I really meant by 'on the fly' is if there are four colours that aren't going to appear on the background or foreground (or arise from a background colour in one bitplane merging with a foreground colour on another bitplane) then you're free to set them to whatever you need for sprites, and if you reserve a few just for enemy sprites, then you can re-allocate them depending on which enemy is about to appear. Leander does this a lot


where do you find all this games? :) I never saw this before!
so Leander use 4 colors for 'sprites' (objects)? But than background use another 4 colors? and main character looks like he have another unique 4 colors? (I do not have time to analyse still image from game, I conclude this from watching youtube video: https://www.youtube.com/watch?v=y3HfkYT7zFI)

joefish wrote:The bitplanes are still held in separate 16-bit words, though the words are then interleaved. Let's say you have a background and a foreground screen to copy from, each with two bitplanes.

Than you for clarifying this! I though that bitplanes (bits) are interleave inside of word! Now I see how it is faster if you use less bitplanes :)
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Re: Shadow Of The Beast Parallax Demo STOS

Postby AtariZoll » Sun Mar 13, 2016 8:01 am

EstTeeEfEm wrote:
Better code would use more RAM for preshifts and 16/32-bit transfers.


This is the route I took, although the preshifts are not built in ram but rather as graphics that are loaded, same memory requirements, just leads to bigger files .. no differences other than waiting for ST to preshift in memory.

as it is in ST version of Uridium

I kid you not, this game is sooo slow i almost started to write my own updated version. if the tiles weren't 8x8 it would be a lot easier :P


I disassembled it completely and done already some updates. The things are that it's not the scrolling what is so slow, but ship control, mostly turning 180 degrees is what makes it almost unplayable. So, need to correct that part of too. Otherwise I'm in process to do blitter based 1px wise scroll, where complete level bitmap is built in RAM before start it - same as did with Giana and Hard 'n' Heavy (considering scroll self - they do level bitmap already). Will need probably still only 512KB RAM . That would work well with 4-bit planes too, but I will leave it as is :D
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Re: Shadow Of The Beast Parallax Demo STOS

Postby EvilFranky » Sun Mar 13, 2016 12:24 pm

Nice demo EstTeeEfEm!

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Re: Shadow Of The Beast Parallax Demo STOS

Postby EstTeeEfEm » Sun Mar 13, 2016 8:06 pm

Nice demo EstTeeEfEm!


Thanks !

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Re: Shadow Of The Beast Parallax Demo STOS

Postby punkrulesok » Tue Mar 15, 2016 9:07 pm

is there meant to be rasters in the sky? As on Hatari there appears to be scanlines flickering at set points due to sync issues?

nice job by the way, i think this will turn in to a bigger project for you :)

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Re: Shadow Of The Beast Parallax Demo STOS

Postby joefish » Tue Mar 15, 2016 9:49 pm

calimero wrote:where do you find all this games? :) I never saw this before!
so Leander use 4 colors for 'sprites' (objects)? But than background use another 4 colors? and main character looks like he have another unique 4 colors? (I do not have time to analyse still image from game, I conclude this from watching youtube video: https://www.youtube.com/watch?v=y3HfkYT7zFI)

Leander isn't doing any parallax, but it is using some palette-based optimisations. I think the background only uses 8 colours so only three bitplanes need to be scrolled. Some of the colours for the player sprite change based on health. And two more colours are changed depending on what bad guy is about to appear. My guess is having the bad guys in 2 colours mean they take less data to store them pre-shifted, and they're quicker to draw.

There's a brief glitch in this system on climbing some stairs, jumping over some red flames, where the edge of a large cart appears also in red. Just as you clear the last flame, it disappears and the wagon turns purple.

But plenty of Amiga games change sprite or palette colours depending on what sprites are about to appear. Agony is another one with obvious 3-colour enemies.

What I find really odd about ST SotB is that the player is drawn in 3 colours all of its own, yet those three are set to very similar muddy shades indistinct from the foreground trees. Bit of a waste.

I've written my own parallax that uses bitplanes - two whole screens, two bitplanes each, with rasters and spare colours for sprites at 25fps. There's also a narrow static horizon detail and moon. No clouds though! One plane does 4 pixel scrolling and the other 1. Note that again on ST SotB it's 8 and 4 pixels, which is the wrong ratio compared to the Amiga version.

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Re: Shadow Of The Beast Parallax Demo STOS

Postby EvilFranky » Wed Mar 16, 2016 11:22 am

That sounds good! Do you have a demo to show us?


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