AuthorTopic: Commercial Critique: The Chaos Engine  (Read 33044 times)

Offline Mr.Modem

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Re: Commercial Critique: The Chaos Engine

Reply #20 on: May 02, 2006, 06:45:10 am
The biggest screenshot archive for Commodore Amiga is Hall of Light: http://hol.abime.net/ You should be able to find all Bitmap Brother games there.
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Offline saimo

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Re: Commercial Critique: The Chaos Engine

Reply #21 on: November 18, 2006, 01:02:38 am
It's definetely late to resurrect this discussion, but maybe the most tech-minded of you will appreciate this ;-)

No you are correct. But he does have a point in that if shadows overlapped with a lot of detail it would look strange. The shadows aren't of course, semi-transparent because you had to do a lot of wizardry to get tints and active transparencies in the Amiga, and it either took AGA chipset or master coder, or both.
Actually in TCE adding real transparencies would have been extremely easy. As some of you have noted, the in-game area (entirely separated from the status bar) has only 16 colors, which means that the BB only used 4 bitplanes. On OCS/ECS 5 planes were perfectly possible, so it would have been just a matter of adding one more plane, setting the palette so that the colors 16-31 were the darker versions of colors 0-15 and blitting the shadow masks on the 5th bitplane. Indeed, almost the same could have been possible even if the game used 5 planes, as OCS/ECS handled also 6 bitplanes: the only restriction, in that case, is that the colors 32-63 were forced to reflect the colors 0-31 with halved brightness (hence, the EHB = Extra Half Brite mode). So, now you'd be probably and rightfully wondering why the BB did not do go for such a simple solution: well, I guess that the problem was that just activating the 5th bitplane would steal more DMA time, making everything (occasionally) slower.

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Look at Lionheart.
Uhm... are you thinking of the water in the first levels? If so, in that case the trick is much different: at a certain Y of the screen the Copper (a very simple 3-instruction coprocessor that had access to the chipset) was instructed to change the palette on the fly - that's basically the same mechanism that allowed to have so many hues for the sky (despite the background had only 8 colors) and the line-by-line parallax. This means that the same effect could not have been used to achieve shadows.


Besides this, somewhere in the thread somebody wonders about full whites/grays... well, I've always been coding for AGA so I don't really know, but, anyway, the AGA chipset for compatibility automatically copies what gets written in the upper 12 bits of color registers to the lower 12 bits, so I'd say that 0xFFF on OCS/ECS equals 0xFFFFFF on AGA (and not 0xF0F0F0).

One final thing: I don't think that the flat tiles were used for performance reasons, because that would have made the tile engine much more complicated for a very little gain; moreover, the gain would not have been constant as it would have depended on the graphics shown, meaning that in certain occasions the engine would have performed faster than in others, which certainly is not as desireable as a steady refresh rate (which, from what I've seen, is what TCE has). I agree with those that say that the flat colors and dithering were chosen to give a better idea of the different levels.

Congratulations to everybody for the nice analysis carried out here!

saimo

Offline Ai

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Re: Commercial Critique: The Chaos Engine

Reply #22 on: November 18, 2006, 02:17:35 am
the shadow masks on the 5th bitplane. Indeed, almost the same could have been possible even if the game used 5 planes, as OCS/ECS handled also 6 bitplanes: the only restriction, in that case, is that the colors 32-63 were forced to reflect the colors 0-31 with halved brightness (hence, the EHB = Extra Half Brite mode). So, now you'd be probably and rightfully wondering why the BB did not do go for such a simple solution: well, I guess that the problem was that just activating the 5th bitplane would steal more DMA time, making everything (occasionally) slower.
Uhm... are you thinking of the water in the first levels? If so, in that case the trick is much different: at a certain Y of the screen the Copper (a very simple 3-instruction coprocessor that had access to the chipset) was instructed to change the palette on the fly - that's basically the same mechanism that allowed to have so many hues for the sky (despite the background had only 8 colors) and the line-by-line parallax. This means that the same effect could not have been used to achieve shadows.
.. And if there was a duplicate color that could appear the same as another color or darker, depending on what raster effect was active where? That would allow you to define 'where the shadow would fall if it was dark enough' and make it visible on a particular range of scanlines. It would mean the scrolling would need to be vertical to do a proper transition, but it's certainly possible.


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Besides this, somewhere in the thread somebody wonders about full whites/grays... well, I've always been coding for AGA so I don't really know, but, anyway, the AGA chipset for compatibility automatically copies what gets written in the upper 12 bits of color registers to the lower 12 bits, so I'd say that 0xFFF on OCS/ECS equals 0xFFFFFF on AGA (and not 0xF0F0F0).
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The question was how it was displayed, though -- which could easily be different from how it was emulated. Probably whatever was simple and good enough looking was done in both the case of AGA-emulation and non-AGA.
Obviously minimalism isn't everything -- but regarding learning art, yeah, it is pretty much everything.

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Offline saimo

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Re: Commercial Critique: The Chaos Engine

Reply #23 on: November 18, 2006, 03:18:13 am
.. And if there was a duplicate color that could appear the same as another color or darker, depending on what raster effect was active where? That would allow you to define 'where the shadow would fall if it was dark enough' and make it visible on a particular range of scanlines. It would mean the scrolling would need to be vertical to do a proper transition, but it's certainly possible.
Uhm... could you elaborate, please? I'm not sure I get what you mean.
The "duplicate colors" idea implies the existence of the extra bitplane mentioned above, but I can't follow you when you talk about "raster effect": if it's not about blitting the shadows (simplest method), but it's about Copper, how could it be done pixel-perfect horizontally-wise given the limitations of horizontal timings (not to mention that it would be much more complicated and time consuming than blitting a 1-plane shadow mask)?

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The question was how it was displayed, though -- which could easily be different from how it was emulated. Probably whatever was simple and good enough looking was done in both the case of AGA-emulation and non-AGA.
True, what should be checked is the actual output of the HW. Though I don't have the equipment to do it (not even an OCS/ESC machine, indeed) nor any specific technical documentation, so the best I can come up with is assuming that AGA compatibility was as close to the original output as possible.

saimo

Offline Ai

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Re: Commercial Critique: The Chaos Engine

Reply #24 on: November 21, 2006, 11:02:54 pm
Uhm... could you elaborate, please? I'm not sure I get what you mean.
you have two identical colors in the palette. one is used to draw a shadow, so you can toggle having a shadow on that tile row via raster effects (changing that palette entry)


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The "duplicate colors" idea implies the existence of the extra bitplane mentioned above, but I can't follow you when you talk about "raster effect": if it's not about blitting the shadows (simplest method), but it's about Copper, how could it be done pixel-perfect horizontally-wise given the limitations of horizontal timings (not to mention that it would be much more complicated and time consuming than blitting a 1-plane shadow mask)?
Well, I find that difficult to believe. The only thing tricky about a raster effect is getting it to run fast enough and timed right.Perhaps the raster timing is lees flexible on Amiga; I remember  games (Switchblade, Stryker and the crypts of Trogan) on the amstrad CPC, a mere 8bit machine running at 4mhz, that changed the entire palette once per scanliine.
Obviously minimalism isn't everything -- but regarding learning art, yeah, it is pretty much everything.

Confidence is an attitude, not a feeling. Directed failure is the engine of confidence.

Offline saimo

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Re: Commercial Critique: The Chaos Engine

Reply #25 on: November 22, 2006, 01:37:55 am
you have two identical colors in the palette. one is used to draw a shadow, so you can toggle having a shadow on that tile row via raster effects (changing that palette entry)
OK. So, I had got it right.

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Well, I find that difficult to believe. The only thing tricky about a raster effect is getting it to run fast enough and timed right.Perhaps the raster timing is lees flexible on Amiga;
Indeed, there are timings issues.
For example, with a LORES screen (that is, ~15 kHz horizontal and 50 Hz vertical), while the Copper writes a value to a color register, the beam roughly draws four pixels, meaning that the Copper cannot be pixel-perfect, horizontally-wise. Moreover, the kind of trick you have in mind requires the CPU intervention which, as fast as the CPU can be, still is deadly affected by the slow CHIP RAM access bottleneck (this also means that even if the effect was applied directly by the CPU - i.e., without Copper at all - still the timings would be just as tight). In a nutshell: simply impossible, if what one is after is creating perfect shadows at any arbitrary horizontal position. And, anyway, asking the Blitter to blit just a single plane (without even having to read any data: just a pure write) not only gives perfect results, but also requires much much simpler code.

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I remember  games (Switchblade, Stryker and the crypts of Trogan) on the amstrad CPC, a mere 8bit machine running at 4mhz, that changed the entire palette once per scanliine.
Indeed, on the Amiga, whether the Copper manages to change the whole palette depends on its size (more colors = more writes), its type (f.ex. a 24-bit palette requires more than the double of writes with respect to a 12-bit one) and the graphical needs (f.ex., if colors are freely used, the Copper should do the operation only during the horizontal blanking... which is definitely very short for this kind of operations).

saimo

Offline Ai

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Re: Commercial Critique: The Chaos Engine

Reply #26 on: November 22, 2006, 05:24:49 am
And, anyway, asking the Blitter to blit just a single plane (without even having to read any data: just a pure write) not only gives perfect results, but also requires much much simpler code.
.. It's a different effect. If at all possible, in such a situation I would want to make use of as many of the 16 extra colors as i can, rather than using them for a fixed-color transparency effect.
Obviously minimalism isn't everything -- but regarding learning art, yeah, it is pretty much everything.

Confidence is an attitude, not a feeling. Directed failure is the engine of confidence.

Offline saimo

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Re: Commercial Critique: The Chaos Engine

Reply #27 on: November 22, 2006, 02:17:45 pm
.. It's a different effect.
Technically, yes. As for the results... at this point, I wonder (again) if whether we're talking about the same thing ???

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If at all possible, in such a situation I would want to make use of as many of the 16 extra colors as i can, rather than using them for a fixed-color transparency effect.
Well, yes, of course that's a matter of choices... solid (like the BB did in TCE) or dithered shadows and more colors to play with, or "proper" shadows and half the colors. IMHO when the pixeller is a master, colors can be sacrificed for the added beauty of the effects that can be achieved - well, better shadows are definitely not a major gain, but double playfields/parallaxes/etc. can be ;)

saimo

Offline EyeCraft

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Re: Commercial Critique: The Chaos Engine

Reply #28 on: November 24, 2006, 07:38:37 am
Far out, you guys are giving me a headache  ;), but its extremely interesting. All hail necro posting  :D

Offline Blick

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Re: Commercial Critique: The Chaos Engine

Reply #29 on: November 24, 2006, 10:55:08 am
Holy crap, it's like having two Neota/AIs and I'm comprehending only half their discussion! It's pretty interesting to see that a game would have to do so many tricks, just to squeeze in transparencies (I think that's what they were talking about).

I feel sorry for the poor bastards that had to brainstorm the process by which they'd create a game with such constraints. It was after the time when games were relatively simple and before the time games were relatively simple to make.