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Genesis VPD vs Saturn VDP

maiki - Jul 3, 2005

		maiki		Jul 3, 2005
			First of all, I am not a coder or anything like that. I just own a Mega Drive and would like to investigate some things here about its VDP compared to Saturn. All I know is that Mega Drive VDP is unfortunately limited to sprites. I do mind it, because many great games like Gunstar Heroes have problems in 2-player modes. On the other hand, Mega Drive VDP is really powerfull - it is extraordinarily complex as for the priorities and collisions of background and sprites. A real arcade adventure here. My question is: I know there are many gurus on this forum, and I would like to ask them if the Saturn VDP is similar to that in the Mega Drive as for the complexity and capability to handle backgrounds and sprites - I mean NOT display them but actually calculate their collisions in particular and (priorities as well, but I guess priorities is not that a problem). so, who is the real winner? Mega Drive with a complex 2D VDp but limited sprites (sadly) or Saturn???

		fonzievoltonov		Jul 3, 2005
			Yo, "All I know is that Mega Drive VDP is unfortunately limited to sprites." I don't understand what you mean by "limited to sprites"... You speak about sprite limit (80total, 20perline/320px per line)? "but actually calculate their collisions" There is no colision calculation with genesis vdp... The vdp just indicates that two (or more) sprites collided during the drawing (it doesnt output a collide table)...

		Borisz		Jul 3, 2005
			He probably means that the Saturn VDP (the VDP2 actually) can handle pictures in a whole.

maiki

Jul 8, 2005

	
	
		
		
			Originally posted by Borisz@Mon, 2005-07-04 @ 07:34 AM



He probably means that the Saturn VDP (the VDP2 actually) can handle pictures in a whole.



[post=136264]Quoted post[/post]

What does that mean? There is no sprite field on Saturn???

As for the Mega Drive - it is a pity they did not elaborated a more powerfull sprite capabilities, at least as Neo Geo, it would be cool to handle around 1000 sprites at once...

		fonzievoltonov		Jul 9, 2005
			Certainely cause the genesis vdp can't handle more than 20+2 redraw per pixel on screen without loosing timings... (if you put 20 sprites on the same area, this makes one draw per sprite plus layer A and B...). Someone here can confirm? Maybe the neo geo has some additional VDP thing that can optimise drawings...

ExCyber

Jul 9, 2005

	
	
		
		
			Originally posted by maiki@Sat, 2005-07-09 @ 05:06 AM



What does that mean? There is no sprite field on Saturn???



As for the Mega Drive - it is a pity they did not elaborated a more powerfull sprite capabilities, at least as Neo Geo, it would be cool to handle around 1000 sprites at once...



[post=136506]Quoted post[/post]

I think Borisz may have meant that Genesis is limited to tiles, i.e. Saturn's VDP2 can handle a direct bitmapped display (although I don't think VDP2 itself has any blitter capabilities, and AFAIK VDP1 renders only into its own buffer so you're bound by the CPU unless you could maybe rig up something with the "DMA through SCU DSP" widget), while the Genesis VDP can only display tilemaps. I think the main reason that the bitmap capability exists on Saturn is for ease of displaying FMV and title (and similar e.g. game over, level completed et. al.) screens, for which tilemapping is basically a hindrance as it saves no memory/bandwidth on these types of scenes and serves only to complicate the task.

As for Neo-Geo, I'm not 100% sure but I think its rendering engine is actually three rather fast sprite engines running in parallel, and their performance almost certainly depends on having a dedicated sprite pattern bus with a large RAM/ROM hooked up to it (Neo carts basically have a dedicated ROM bank and bus for every major component, which is why they have two large circuit boards and are/were inordinately expensive).

		mrkotfw		Jul 10, 2005
			using tile does indeed save some memory. what if it's a patterned background? you can probably display that background in 2-3 tiles min. as for the map data, it can probably be easily compressed. it does complicate things a lot. the programmer should also have no problem doing any of this anyways! there are many many reasons for using tile rather than bitmap, one of them is being able to use multiple layers. as for the 1,000 sprites, i don't think that would be possible because where would you store all the tiles? you can't possibly use the space that is used for the backgrounds! there are tricks to allow more than the allowed sprites, using a horizontal blank effect. i don't know how it works exactly, but i know some people need it to display a lot of sprites.

Mask of Destiny

Jul 10, 2005

	
	
		
		
			Originally posted by Piratero+Mon, 2005-07-11 @ 08:22 AM-->QUOTE(Piratero @ Mon, 2005-07-11 @ 08:22 AM)there are many many reasons for using tile rather than bitmap, one of them is being able to use multiple layers.[/b]

There is no reason you couldn't implement multiple layers with a bitmapped display. The reason for using tiles is strictly for saving space and saving memory bus bandwidth. Even with DMA, there isn't enough bandwidth on the main memory bus to draw to every pixel on the screen; however, it takes relatively little bandwidth to rewrite the name table to say which tiles are used where.