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TG16/PCE sprite capability's question
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Tomaitheous
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PostPosted: Tue Feb 17, 2009 5:17 am    Post subject: Reply with quote

GHS wrote:
So the SGX doubled the sprites to 128 on screen. More sprites so you could have 352 ress instead of 256 action games. I just figured out something, in 256 ress you could make a full 3rd background layer, I think.
O the possibility's if they incorporated it in to the CD, one could dream.


Yes, you could make a 3rd BG layer with the sprites in 256 mode, but to be honest I'd rather use those sprites for something else - with a few exceptions Wink

Quote:
But, I read that the CPU couldn't keep up withe the VDCs, so its meaningless.


Meh - just a myth/urban legend. The fact that the other VDC has its own 64k of vram, means there's even less updating to do. And the fact that the CPU can write to either VDC's VRAM during active display, makes it really convenient. It's not like the CPU's driving the display. I never had any problems or extra resource taking care of the second VDC.

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How dose the PCE compare (in sprites) to the MD and SNES (advantages, disadvantages)?


Best to worse
Number of palettes: PCE ( 16 ) ,SNES( 8 ) ,MD( 4 )

Sprite vram location: PCE(free range) and MD(free range), SNES (limited between two smaller banks - no cross over).

Sprite size(versatility): MD, PCE, SNES. MD has nice 8x8 cell increments between min and max size, PCE coming in second but with less efficient 16x16 cell size but larger max size, SNES in last because you can only have 2 different sprite sizes onscreen at the same time.

Sprite scanline limit: SNES (272 pixels to its 256pixel screen width), MD, PCE. I give the edge to Megadrive because the sprite pixel limit ration is even with the 320 pixel mode. But for 256 pixel mode, they have the same ratio.

Cells per scanline: SNES (32 8x8 cells), MD (16 for 256 or 20 for 320 mode), PCE (16 for all resolution).

The SNES sprite configurations are a bit strange. It has the largest cells per scanline and the best ratio for the screen width, but limited from only having two different sizes onscreen at once. The VRAM bank thing can be limiting and/or adds complexity to the design. The sprites size have a convoluted interleaved sprite layout. They also have a dedicated 8 palettes just for sprites.

The MD sprites, while hindered to the same 4 palettes that the background uses, has a nice range sprite sizes in steps of 8x8 cells in both directions. Although the max sprite size is 32x32, it's worth the trade off in my opinion. With 8x8 cell steps, you can really optimize to remove or reduce flicker. The number of cells and pixels per scanline linearly scales with the screen width, which is really nice.

The PCE sprites have a dedicated 16 palettes just for sprites. The cell size is not as optimal as the SNES or MD, but cell configuration is large than MD and less convoluted of SNES. The sprites are not stored in the same format as tiles, like with the SNES and MD. A bit of interesting info: If a PCE game optimizes sprite graphics around 16x16 segments and is ported to the Megadrive, the MD advantages of 8x8 cell size won't really be taken advantage of. You can see this in the Lords of Thunder port to the SegaCD as the kept the res the same as the original. Of course, most PCE games don't even optimize for its native cell size Rolling Eyes

Not really a sprite, but the PCE can draw pseudo sprites like long horizontal lasers by stalling the VCE without effecting the sprite pixel per scanline limit. It comes at a tiny cost of ~400 cycles per scanline instance . In perspective, there are 120,000 cycles per 1/60 frame . (This works in both NTSC and RGB output.)
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GHS
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PostPosted: Fri Feb 20, 2009 12:32 am    Post subject: Reply with quote

What is the max sprites on screen for the SNES & MD and whats the SNES max sprite size. I read that the MD had 2 color pallets for sprites and 2 for background. Theres allot of misinformation out there on the counsels, where do you get your info?
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Tomaitheous
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PostPosted: Fri Feb 20, 2009 2:33 am    Post subject: Reply with quote

GHS wrote:
What is the max sprites on screen for the SNES & MD and whats the SNES max sprite size. I read that the MD had 2 color pallets for sprites and 2 for background.


I read that as well from one doc, but it's not true. There are a total of 4 palettes on the Genesis in which the BG and the sprites have access to. In realistic terms, it's probably safe to assume most games divide the palettes in half to management reasons. You can see this when open up the debugger and look at the palette info and changing it manually to see what it effects. Since you can't access colors of two palettes in a single tile or sprite, four 15 color palettes it really limiting. Really limiting.

The maximum number of sprites onscreen for SNES is 128 and 64 for 256x224 mode & 80 for 320x224 mode of the Genesis. The max sprite size for Genesis is 32x32, 64x64 for SNES, and 32x64 for PCE.

But with the SNES, you're stuck with only two sizes for whole frame. If you choose 64x64 for the second size, then you'd probably want to choose 16x16 for the first size, else you're really eat up that 128 entry table with 8x8 sprites and the overhead of doing the group/matrix in software.

Quote:

Theres allot of misinformation out there on the counsels, where do you get your info?


Official docs, test docs, and dev forums. For SNES, Anomie's doc is even better than the official 'SFX' dev docs form Nintendo (IMO) because of how many damn registers and special cases there are (it's incredibly overly complex in design and function). For Genesis, the official dev docs provided everything you need to know.
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GHS
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PostPosted: Sat Feb 21, 2009 3:24 pm    Post subject: Reply with quote

I was going to save this for a future topic (resolutions & colors) but since this is about sprites I think its best here.
All sprites have 15 colors (not counting the 16th transparency) for PCE, MD and SNES. Is there a way to increase the color limit, and if there is how many ways are there?
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Tomaitheous
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PostPosted: Sat Feb 21, 2009 9:33 pm    Post subject: Reply with quote

GHS wrote:
I was going to save this for a future topic (resolutions & colors) but since this is about sprites I think its best here.
All sprites have 15 colors (not counting the 16th transparency) for PCE, MD and SNES. Is there a way to increase the color limit, and if there is how many ways are there?


Only by overlapping one sprite onto another for up to 30 colors. Of course thing increase the chance for sprite drop out per scanline. The other thing to note about is that the 15 color limit applies to the whole sprite, not each individual sprite cell (be it 8x8 or 16x16). So if you have a 32x32 sprite, the whole thing is using 1 palette and 15 indexed colors. You'd have to divide the sprite into 32x16 upper and 32x16 lower if you needed different colors in the lower half. 15 colors per sprite is not so bad. Lots of arcade systems have the same limitation (Neo Geo and Capcom CPS-1), of course they can overlap when needed without much worry about sprite drop compared to the home consoles.
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GHS
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PostPosted: Sun Feb 22, 2009 2:20 pm    Post subject: Reply with quote

I read something about MD's "shadow & highlight". How dose that work?
Can the sprite or tile have both S&H on it dose it Shade or brighten the whole sprite or tile, or can it only have one of each? Can the SNES and PCE or SGX do that?
This would add more color or value, I think.
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