chunky pixel mode

[lassie]

Hi i have been thinking about 3D on Amiga and read about something called chunky pixel mode, if they had used that in an Amiga 1200 and CD32 would it have made the Amiga better at 3D games? or should there more to it, maybe more ram etc?

I have an Super Nintendo and Sega Cd and they are quite good at making (fake) 3D games but they also have something called mode 7. But Sega CD only have 128 kb ram but it sure can make some decent 3D games, i know it is not real 3D but it looks great. so i have been thinking what Amiga could have done to keep up with the newer games from the 3D era. But i have seen some demos on a stock Amiga 1200 and they were quite cool 3D demos

[NovaCoder]

Hi i have been thinking about 3D on Amiga and read about something called chunky pixel mode, if they had used that in an Amiga 1200 and CD32 would it have made the Amiga better at 3D games? or should there more to it, maybe more ram etc?

A chunky mode would have helped in the early days but you need more than a chunky mode to do decent 3D.

[Hattig]

A chunky pixel mode would have helped with the early-style 3D games which used software rendering, especially ray-casters like Doom.

But other things would have been better - fast RAM as default on the CD32, a SIMM slot in the A1200 for easy Fast RAM addition. Hardware changes include a faster, 32-bit-wide blitter and explicit polygon rendering acceleration hardware.

[bloodline]

Chunky pixel mode, put very simply mean that the CPU only needs a single write to the memory per pixel. On the Amiga, due to the planar pixel mode, the CPU has to make 8 separate writes to the memory per pixel (for 256 colours), this can be optimised a bit... But it's still quite an overhead when compared to chunky pixel mode.

[Digiman]

Put simply if Amiga had chunky pixel mode Doom would run faster on Amiga than it does. Or possibly even a simple 256 colour game in super hi-res interlace mode (which is pretty much only good as a static screen due to speed on AGA)

And the reason we had the insane architecture of 8 bitplanes not byte per pixel in 256 colour displays was...........

[bloodline]

Put simply if Amiga had chunky pixel mode Doom would run faster on Amiga than it does. Or possibly even a simple 256 colour game in super hi-res interlace mode (which is pretty much only good as a static screen due to speed on AGA)

And the reason we had the insane architecture of 8 bitplanes not byte per pixel in 256 colour displays was...........

... Because AGA was little more than a bug fix to ECS, and back in the mid 80's bitplanes made sense as you could very carefully control the amount of memory used in your gfx... Once ram became cheap in the 90's bitplanes were a nasty bit of legacy

[Hattig]

And the reason we had the insane architecture of 8 bitplanes not byte per pixel in 256 colour displays was...........

Commodore cheaping out.

It probably wouldn't even have been much logic to implement (compared to the rest of the logic). Instead of reading up to 8 words from bitplanes at different addresses, just read 8 words sequentially, and interpret the data differently.

I'm guessing the data from each bitplane was read (32 bits at a time) into shift-registers (one per plane) on the chip, and that the data was shifted out (at the pixel clock rate) as a number that was fed into the colour palette (CLUT) to get the RGB display value for that pixel.

So to implement a byteplane you would just need to feed those 8 shift-registers differently, or have an chunky shift-register that shifted 8 bits at a time.

[Mrs Beanbag]

... Because AGA was little more than a bug fix to ECS, and back in the mid 80's bitplanes made sense as you could very carefully control the amount of memory used in your gfx... Once ram became cheap in the 90's bitplanes were a nasty bit of legacy

It also allowed you to do cool stuff like hardware parallax scrolling, easy masking of bobs (in fact it generally makes much more sense with the blitter), really there are a lot of ways in which bitplanes are better for the 2D, sprite-based games you got in the '80s and early '90s, it was only when Doom came out, and then Quake, and everyone got excited about 3D texture mapping that chunky mode became... a game changer.  Suddenly a fast CPU was the most crucial factor, and all the Amiga's clever custom-chip hardware was all for naught.

[Crumb]

Hi i have been thinking about 3D on Amiga and read about something called chunky pixel mode, if they had used that in an Amiga 1200 and CD32 would it have made the Amiga better at 3D games? or should there more to it, maybe more ram etc?

I have an Super Nintendo and Sega Cd and they are quite good at making (fake) 3D games but they also have something called mode 7. But Sega CD only have 128 kb ram but it sure can make some decent 3D games, i know it is not real 3D but it looks great. so i have been thinking what Amiga could have done to keep up with the newer games from the 3D era. But i have seen some demos on a stock Amiga 1200 and they were quite cool 3D demos

For SNES-like*mode-7 style effects check out "Brian The Lion", it was coded by sceners and they programmed blitter to make it rotate and zoom bitmaps with higher accuracy than SNES
and quite fast (the intro screen rotozoom runs at 25fps on a stock amiga with no fastmem)
http://www.youtube.com/watch?v=m-IDcTW8JQ4

Chek out minute 9:24, 9:30 to see the big platforms rotated using Amiga Blitter.
http://www.youtube.com/watch?v=m-IDcTW8JQ4&feature=player_detailpage#t=564s

IMHO*the problem with AGA was
1. Not enough sprites
2. That caused that people used blitter to draw the remaining gfx but it was more or less as fast as the OCS/ECS ones
3. Since blitter was slow some coders of modern games draw the stuff in fastmem and copy to chipmem and that's when you realize chipmem's top speed of 7MB/s with a good accelerator (faster than most ISA cards) is not enough
4.*Chunky modes would have been useful at the beggining with slow cpus but from 040 upwards you can perform c2p as fast as you perform a copy from fast to chip. Even if you had a chunky mode if your game gfx are moderately complex you probably won't like to draw byte by byte to chipmem, you'll prefer to do that in fastmem and copy the result to chipmem at the end. So with 040+ cpus chunky modes are not a problem. In fact first IDSoftware games ran in planar 16-colour EGA mode on peecees and ray^tscc showed some years ago wolf3d was possible on a 8Mhz Atari

More sprites would have made a real difference. Check out Neo Geo games. These are 2D only but impressive anyway. CBM*should have added more sprites or a 32bit blitter and that would have made a lot of difference in the quality of Amiga games. Chunky games usually looked like sh*t anyway.

Although challenges are always fun (doing chunky games on Amiga) I think more effort should have been done in taking advantage of AGA+fastram and doing some great neo-geo like games.

[Hattig]

More sprites would have made a real difference. Check out Neo Geo games. These are 2D only but impressive anyway. CBM*should have added more sprites or a 32bit blitter and that would have made a lot of difference in the quality of Amiga games. Chunky games usually looked like sh*t anyway.

Although challenges are always fun (doing chunky games on Amiga) I think more effort should have been done in taking advantage of AGA+fastram and doing some great neo-geo like games.

Adding more sprites would have been difficult due to the nature of Amiga sprites - a scanline of each sprite is loaded into the chip during HBLANK, and there's only so much bandwidth available, which coincides with the AGA sprite size and count. Sprites were an after-thought on the Amiga. To do them like the NeoGeo/etc there would have had to be a separate sprite memory, scanline buffer and memory bus so that accesses to sprite data could be done at any time.

The best option would have been a 32-bit blitter and a faster chipram bus. The latter would have helped the sprite count too.

[runequester]

Chunky mode would have helped, but processing power was more of a bottleneck in my opinion. 030's vs 486's isn't really any reasonable comparison for a CPU intensive game.

[Hattig]

Chunky mode would have helped, but processing power was more of a bottleneck in my opinion. 030's vs 486's isn't really any reasonable comparison for a CPU intensive game.

But the 486s were in £1000+ systems, and the A1200 was a £400 (then £300) system.

Which brings us onto the other failing: No £600 A1230 with 40MHz '030 and 4MB RAM at release. Upselling - Commodore hadn't heard of it, apart from that hard drive included SKU.

At Release:
A1200 2MB '020 14MHz: £399
A1200 4MB '020 14MHz: £479
A1200 4MB '030 25MHz: £549
A1200 4MB '030 40MHz: £599
A2200 4MB '030 40MHz: £799 (A1200 in desktop case w/ separate keyboard)

People would have easily been persuaded to get a higher level A1200 in shops because the price increments aren't too shocking.

[runequester]

But the 486s were in £1000+ systems, and the A1200 was a £400 (then £300) system.

Which brings us onto the other failing: No £600 A1230 with 40MHz '030 and 4MB RAM at release. Upselling - Commodore hadn't heard of it, apart from that hard drive included SKU.

At Release:
A1200 2MB '020 14MHz: £399
A1200 4MB '020 14MHz: £479
A1200 4MB '030 25MHz: £549
A1200 4MB '030 40MHz: £599
A2200 4MB '030 40MHz: £799 (A1200 in desktop case w/ separate keyboard)

People would have easily been persuaded to get a higher level A1200 in shops because the price increments aren't too shocking.

Oh, I agree completely. When people have brought this up in the past, the response is usually some sort of resigned "well, PC's were faster anyways, so nobody would have bought it", but the stock 1200's sold extremely well. A 1200 with even a bit of FAST RAM and either a faster 020 or a decent 030 would have sold just as well.

[Mrs Beanbag]

Chunky mode would have helped, but processing power was more of a bottleneck in my opinion. 030's vs 486's isn't really any reasonable comparison for a CPU intensive game.

This is true, an A1200 with native 68060 would have been truly awesome.  A1600?

[Pentad]

... Because AGA was little more than a bug fix to ECS...(

I could not agree more.  The Amiga was wonderful in 1985 but Commodore never did anything to the hardware after.  Oh, there were minor upgrades but the Amiga's amazing designs of the 80's became a liability in the 90's.  

I could be wrong about this in 1988 didn't R&D show some amazing chip designs that would have be the next gen for the Amiga?  I thought I recalled that they said -looking back- it would have been like the Voodoo I from 3DFX for the PC years later.  

Sad, really....

-P