Trixter: Blast Processing wasn't just fluff after all

[Neb6]

The Genesis probably doesn't have a blitter at all. Reportedly the SNES doesn't and some cartridges have implemented a basic blitter as an assist chip.[/QUOTE]

Well, according to this Genesis emulator programming change-list, it looks like the Genesis does have a blitter:

http://www.aep-emu.de/PNphpBB2-file-...c-t-19870.html

Performing shifting and masking operations on a 68000 CPU draws far too many cycles for it to be anywhere close to being efficient. That had already been proven on the earlier 6809. As for DMA, that's just direct memory access for whatever piece of hardware for the purposes of freeing up CPU cycles.

[Jorpho]

Yes, you linked to that before. Rather than speculating, you could just, y'know, ask the emulator author. If it's really a hardware feature of the Genesis, shouldn't there be references to it in a whole lot of other emulator documentation?

The first time I read about blitting was in conjunction with WinG (links to http://en.wikipedia.org/wiki/Bit_blit ), which does not inherently require hardware.

[Niku-Sama]

for some reason this isnt new to me......


i feel old now

[Neb6]

Yes, you linked to that before. Rather than speculating, you could just, y'know, ask the emulator author. If it's really a hardware feature of the Genesis, shouldn't there be references to it in a whole lot of other emulator documentation?

The first time I read about blitting was in conjunction with WinG (links to http://en.wikipedia.org/wiki/Bit_blit ), which does not inherently require hardware.

Well, there's always this:

http://www.google.ca/patents/US5880739

Search word = Sega

[Ed Oscuro]

Okay, I forgot about the VDP, too, which is probably used for blitting functions. Point about the 68000 being slow for scanline and other operations without a blitter.

@ Jorpho: "Blitting" can be done in software, sure, but a blitter would be hardware.

In the case of the Sega patent filing above, that looks like an early 3D era patent, where a blitter (or some kind of other means of getting pixel fill rate going) is absolutely necessary, unquestionably.

[Neb6]

Okay, I forgot about the VDP, too, which is probably used for blitting functions. Point about the 68000 being slow for scanline and other operations without a blitter.

@ Jorpho: "Blitting" can be done in software, sure, but a blitter would be hardware.

In the case of the Sega patent filing above, that looks like an early 3D era patent, where a blitter (or some kind of other means of getting pixel fill rate going) is absolutely necessary, unquestionably.

The SEGA patent that the Compaq Blitting patent is referencing seems to be describing something that sounds a lot like the Genesis/Mega Drive version of Sonic:
http://www.google.ca/patents/US5513307

See figures 17, 20A, and 43A.

Excerpts:

"It is possible that the character could jump while in the process of traversing the shuttle loop. Since the sloop twists like a corkscrew, the result of such a player jump could be that, rather than going upward, the character falls down off the loop. For example, if the character jumps from the left inclined or twisted side of the loop as the sprite runs to the right, the character will end up falling downward rather than jumping upward as indicated by the trajectory shown by arrow 120 in FIG. 16C. In that case, the horizontal speed of the character is maintained, as he falls downward. If, on the other hand, the character jumps while on the inclined portion on the right side of the shuttle loop as it runs to the left, then it will be seen to follow the trajectory 122 as its horizontal speed to the left is maintained and as it falls downward. Its fall will be stopped when it hits the surface 124."

"race through the playfield trying to accumulate points by surmounting obstacles, slaying enemies or gathering "magical rings", for example.

[blue lander]

I wrote a little "space invaders" style game for the Genesis about 10 years ago for fun so my memories on this are a little fuzzy, but as I recall you could do basic bit blitting with the GPU. Like, you could have it shift a bunch of data at once, or move a block of data from RAM to VRAM. It was pretty simple compared to what an Amiga could do. Useful for scrolling but not much else.

[ccovell]

I wrote a little "space invaders" style game for the Genesis about 10 years ago for fun so my memories on this are a little fuzzy, but as I recall you could do basic bit blitting with the GPU. Like, you could have it shift a bunch of data at once, or move a block of data from RAM to VRAM. It was pretty simple compared to what an Amiga could do. Useful for scrolling but not much else.

But... that's just DMA transfer. IIRC, the SNES and TG-16 can both do DMA, block transfers, high-speed VRAM-to-VRAM transfers, etc. I think the difference between block moves and "blitting" is that in blitting you can combine bitmap data from one source, logically AND or OR it with a mask, and then overlay the product on some destination bitmap. <--- the Amiga did this in hardware.

I have my doubts the Genesis could do that in hardware. If it was done in software, then "blast processing" remains bullshit as any game console can do any kind of processing in software.

[blue lander]

I think you could do bit level shifts, but I don't remember any fancier data transformation abilities. It was more like an off-the-shelf MMU. It reminded me a little of the Atari ST.

Zophars domain used to have a really good document on how the VDPs in the Genesis and SMS worked, I'm sure it's still out there somewhere.

[TonyTheTiger]

I have my doubts the Genesis could do that in hardware. If it was done in software, then "blast processing" remains bullshit as any game console can do any kind of processing in software.

Depends on how you define "bullshit." Something can be technically true even if it isn't all that special or downright insignificant. Given that this era in particular was notorious for relatively meaningless buzzwords in general (the entire bit wars come to mind) "blast processing" doesn't seem any worse than all the rest of the marketing shenanigans that went on.

[Jorpho]

Zophars domain used to have a really good document on how the VDPs in the Genesis and SMS worked, I'm sure it's still out there somewhere.

Probably http://www.romhacking.net/documents/231/ ? See also the other Genesis docs.