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Man, Blast Processing is not what I thought it was. . . .


Kirk_Johnston

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"The fact is that Blast Processing is such a hardcore, low-level application of the Mega Drive hardware that, astonishingly, it was never used in any shipping games and only in recent years has the technique been successfully mastered. And even then, its actual application in games is severely limited, with some interesting, but not exactly game-changing results ... But secondly, and perhaps more pressingly, Blast Processing essentially uses the entirety of the 68000's CPU time. You can run Blast Processing on a Mega Drive game, but you'd be unable to run anything with it ... So it's useless for standard cartridge games [other than for static high-colour images] ... Throughout the machine's lifetime, clever coding produced an almost generational leap in the effects seen in Mega Drive titles - but Blast Processing, unfortunately, wasn't one of them." - Eurogamer

 

Here's a video of what real Blast Processing is: https://www.youtube.com/watch?v=rvvL6S5Buiw

 

I feel like I learn something new about these old consoles every day.

Edited by Kirk_Johnston
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I remember reading something about that before, didn't know there was a video.  I mean it makes sense, if you go low enough level into a core like that you can 'blast process' something to such extremes it uses up every cycle basically moving the system to a halt for a result until the blasting is loosened up and other processes can resume/begin again.  So in the end, it was a fuzzy half truth but in reality a big ass marketing lie to get attention, which Sega was all about in the day because they suffered the equivalent of tiny wang big sportscar over-compensation type mentality back then.

 

I'm sure there are some good examples out there in some visual formats of what this could result in as it says there, high color images, and maybe that's the peak best result.  One would wonder just how high color, I don't have time for the video if that's all covered, but would it still have rivaled the modes the SNES or maybe even the TG16 and NeoGeo could do to spit out an insane level of colors also on a static display?

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14 minutes ago, Tanooki said:

I remember reading something about that before, didn't know there was a video.  I mean it makes sense, if you go low enough level into a core like that you can 'blast process' something to such extremes it uses up every cycle basically moving the system to a halt for a result until the blasting is loosened up and other processes can resume/begin again.  So in the end, it was a fuzzy half truth but in reality a big ass marketing lie to get attention, which Sega was all about in the day because they suffered the equivalent of tiny wang big sportscar over-compensation type mentality back then.

 

I'm sure there are some good examples out there in some visual formats of what this could result in as it says there, high color images, and maybe that's the peak best result.  One would wonder just how high color, I don't have time for the video if that's all covered, but would it still have rivaled the modes the SNES or maybe even the TG16 and NeoGeo could do to spit out an insane level of colors also on a static display?

Interestingly, I've not really found many/any great examples of SNES static images going above the default 256 colours, even though it's totally capable of this just by using the likes of colour math and/or direct colour alone (and without any special hacky tricks whatsoever, not even simple raster interrupts). And, also just as strangely, I've yet to actually see a clear example of a good Genesis Blast Processing image too. They're surely out there, but they are apparently very elusive for both consoles.

 

It's somewhat more easy to find good looking 256-colour SNES images though, and I even posted a handful of them myself previously:

 

https://inceptionalnews.wordpress.com/2022/10/23/snes-mode-3-images-can-look-gorgeous/

 

I'd kinda love to see a handful examples of really good static images from each console where they go well above their typical colour limits, just to see what that looks like in actual practice on each console respectively.

 

There is a link in the Digital Foundry video for a Blast Processing Genesis demo, but I downloaded it and it didn't work for me. All I saw was a bunch of difference coloured vertical lines on the screen.

 

Maybe one day someone will post a good set of such images for each system that we can all easily access via a quick Google search and the like.

Edited by Kirk_Johnston
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Dude just go run Titan Overdrive 2 on your PAL Mega Drive. I think that has Blast Processing in it. It also has what appears to be transparency but is probably just shadow/highlight, although I have no idea how this was accomplished, so don't ask.

 

20221215_165714.png.afb5aebb450fcc36d9179322ac51fe25.png

 

You do have a PAL Mega Drive, right? I don't, so I am going to hell because of that, but it also means I have to use regular Titan Overdrive on my Japanese Mega Drives instead, but that does have it for sure, and this is what it looks like with a glitchy out-of-place sprite on my fake "real" Japanese Mega Drive that you probably better know as the Analogue Pocket.

 

20221215_170839.png.855841b393146e2fe571100febeb7712.png

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6 hours ago, Steven Pendleton said:

Dude just go run Titan Overdrive 2 on your PAL Mega Drive. I think that has Blast Processing in it. It also has what appears to be transparency but is probably just shadow/highlight, although I have no idea how this was accomplished, so don't ask.

 

20221215_165714.png.afb5aebb450fcc36d9179322ac51fe25.png

 

You do have a PAL Mega Drive, right? I don't, so I am going to hell because of that, but it also means I have to use regular Titan Overdrive on my Japanese Mega Drives instead, but that does have it for sure, and this is what it looks like with a glitchy out-of-place sprite on my fake "real" Japanese Mega Drive that you probably better know as the Analogue Pocket.

 

20221215_170839.png.855841b393146e2fe571100febeb7712.png

Unfortunately, I don't actually have either a real Genesis or SNES these days. Best I have access to is emulators.

 

No idea how the first effect is achieved, but it looks cool.

 

That bottom image always looked a bit strange to me with the kind of dithered look across the whole thing, but it's cool to see the extra colours in use. Would have expected there to be a lot more examples of actual images to check out by now though, like real paintings and photos and stuff like that but running with Blast Processing so they represent the best the Genesis can make them look and display what it's capable of.

 

It's strange though, because the SNES can manage this with 256 colours, and I'm hoping to see some similar 512-colour Blast Processing results on Genesis:

 

1.png.13c49565e90809791c704c032ac8c651.png

2.png.62edd237a6587eca251a5d415532b754.png

3.png.4ade1b5e7ae4a32cf6c6a58c25099f4b.png

4.png.e976840eb1872e3e1f68e58abb2492cd.png

5.png.1f3d545429db58ab86db2ea428f9cc35.png

 

Just to check, is the Blast Processing limited to the specific 512 colours of the Genesis' master palette?

 

PS. That Titan Overdrive 2 demo is definitely one of the best on the scene, and, imo, better than any similar demos for the SNES thus far.

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8 hours ago, Steven Pendleton said:

Dude just go run Titan Overdrive 2 on your PAL Mega Drive. I think that has Blast Processing in it. have no idea how this was accomplished, so don't ask.

20221215_165714.png.afb5aebb450fcc36d9179322ac51fe25.png

Actually, I think that is indeed a version of the shadow/highlight mode at work. I think there is the main pattern in the background, with the words/logo having some opaque gray parts and some cut-out parts that show the pattern through them. And the cut-out parts have the highlight effect applied, so it looks like the colours there are slightly less dull than normal, which makes it seem like the words/logo is semi-transparent in those areas. It's a neat visual effect that's executed well here within the Genesis' limitations.

 

At least that's how I think it's done anyway.

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2 hours ago, Kirk_Johnston said:

Best I have access to is emulators.

That's why the Blast Processing demo doesn't work; most of the software emulators out there will break when you try to run the stuff that you need super-accuracy for. Overdrive 2 is completely insane, and there are very few emulators that I know of that will run it. BlastEm is one (and the most accurate software emulator for the system unless something changed since I last checked), and the Mega Sg is another. Should probably work on MiSTer. It works on the Pocket but has graphical glitching in one scene using one of the two cores for the system, but I have not tested it on the other core yet, which may have been ported over from MiSTer, in which case it should work. Hell, Overdrive 2 apparently even breaks on some real PAL Mega Drives. Force it to run on a Genesis or Japanese MD against its own will (and its region lock) and it will desync itself and crash shortly after it starts.

 

Here is the DF Blast Processing stuff on the Pocket.

 

20221215_165154.png.db8f74a699a07e82800b62f3aae7886d.png

 

20221215_165205.png.dd76ca1501a0b8f2417eb27dfe51cf78.png

 

20221215_165239.png.1119bc41caff8533f72db0cd46b4d179.png

 

2 hours ago, Kirk_Johnston said:

Just to check, is the Blast Processing limited to the specific 512 colours of the Genesis' master palette?

Unknown, but I believe so. @Chilly Willy is probably the one to ask. It is strange that it does look pixelated, however; the timings for this are apparently quite difficult, which may be why there are basically no examples of Blast Processing and why those that do exist look the way they do, but I don't know the specifics.

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3 minutes ago, Steven Pendleton said:

That's why the Blast Processing demo doesn't work; most of the software emulators out there will break when you try to run the stuff that you need super-accuracy for. Overdrive 2 is completely insane, and there are very few emulators that I know of that will run it. BlastEm is one (and the most accurate software emulator for the system unless something changed since I last checked), and the Mega Sg is another. Should probably work on MiSTer. It works on the Pocket but has graphical glitching in one scene using one of the two cores for the system, but I have not tested it on the other core yet, which may have been ported over from MiSTer, in which case it should work. Hell, Overdrive 2 apparently even breaks on some real PAL Mega Drives. Force it to run on a Genesis or Japanese MD against its own will (and its region lock) and it will desync itself and crash shortly after it starts.

 

Here is the DF Blast Processing stuff on the Pocket.

 

20221215_165154.png.db8f74a699a07e82800b62f3aae7886d.png

 

20221215_165205.png.dd76ca1501a0b8f2417eb27dfe51cf78.png

 

20221215_165239.png.1119bc41caff8533f72db0cd46b4d179.png

 

Unknown, but I believe so. @Chilly Willy is probably the one to ask. It is strange that it does look pixelated, however; the timings for this are apparently quite difficult, which may be why there are basically no examples of Blast Processing and why those that do exist look the way they do, but I don't know the specifics.

Thanks for posting those example images. :D

 

Do you know what those large bars of solid colour are at the bottom of the images?

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8 minutes ago, Kirk_Johnston said:

Do you know what those large bars of solid colour are at the bottom of the images?

Unknown, but that is how it renders on my real Mega Drives as well, so it is intentional for whatever reason.

 

These also probably look better over composite than RGB, but I don't really feel like finding my composite cables to find out, as I have no idea where they are.

Edited by Steven Pendleton
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22 minutes ago, Steven Pendleton said:

Unknown, but that is how it renders on my real Mega Drives as well, so it is intentional for whatever reason.

 

These also probably look better over composite than RGB, but I don't really feel like finding my composite cables to find out, as I have no idea where they are.

Could be they were deliberately leaving gaps to have some text at the bottom or something like that, maybe as you might have in a typical cutscene or similar.

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The MD uses BGR444 where the lsb of each color is ignored, for 3 bits per color, or 512 total colors. This mode of display I tend to call Direct Color DMA for obvious reasons: the pixels are direct color mode (BGR444 in big-endian format with the lsb of each color ignored), and are DMA'd to the background color register of the VDP. Filling the whole screen requires a bitmap that is 198*224 (for NTSC, PAL could be taller), where 160 of the 198 pixels is visible. That 198 pixels is the entire display line, including the horizontal blanking period. Yes, the whole overscan region is visible. Shifting the 160 wide image left and right can put part of it in one side of the overscan or the other. You COULD make your software use the overscan region if you want, but why would you? In narrow mode, the dimensions of the bitmap is 161*224, where 128 pixels are the normal visible line.

 

You don't have to fill the entire display side to side, but the bitmap is still 198 or 161 words wide, and all will be DMAd to the VDP. You don't have to use all 224 lines, either. Stopping the DMA early leaves more time for the CPU. In fact, set the DMA for something like 198*180 words, and when the cpu starts as the DMA ends, set the VDP to show a normal graphics HUD under the DCD region.

 

In any case, yes, DCD pixels are two normal pixels wide. It can be any of the possible 512 colors the VDP can show. This limits what this mode is good for. Anything that needs fine detail is not going to get it, so that is right out. That would be better done with the normal 320 wide graphics.

 

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