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Saturn transparencies

it290 - Jan 6, 2005

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ExCyber

Jan 16, 2005

	
	
		
		
			I suppose the Saturn doesn't store textures in the VDP1 ram

I'm pretty sure it does. Where else would it get them from?

edit: never mind, I guess you meant the VDP1 framebuffers.

M3d10n

Jan 17, 2005

	
	
		
		
			Originally posted by ExCyber@Sun, 2005-01-16 @ 04:45 AM



I'm pretty sure it does. Where else would it get them from?



edit: never mind, I guess you meant the VDP1 framebuffers.



[post=127845]Quoted post[/post]

Yeah, I meant storing textures and the framebuffers on the same RAM. Even if it does that, would the VDP1 allow drawing outside the backbuffer area?

I lean towards the software renderer theory for Burning Rangers because it would make more sense on the Saturn if getting the VDP1 to draw to an off-screen buffer and transfer the result to the VDP2 bitmap RAM proved unfeasible.

Skilled programmers with Saturn experience (Sonic Team) would have no trouble getting the slave processor to handle drawing directly into a format the VDP2 can deal with. AMOK's voxel engine was an impressive demonstration on how well a dual processor system like the Saturn can deal with software rendering.

		Quakester2000		Jan 22, 2005
			From the Saturn FAQ By John JHokansonJr ------ 5.1 Can the Saturn perform transparency and light sourcing effects? ------------------------------------------------------------------- The answer depends on the context in which this question is asked. The Saturn is at least capable of generating transparent layers for use in 2D spirte-based images. Furthermore, pseudo 3D transparencies (like the water in Panzer Dragoon) are also possible. These effects can be done directly by the VDP2. If anybody doubts this (and there have been a few), you can check out games such as Astal, Darius Gaiden, and Radiant Silvergun. These are but a few examples. You can also simply powerup your Saturn and check out the system settings. The menu screens themselves provide a glimpse at the Saturn's layered transparency effects. Effects such as these are nothing really new, as they were seen earlier on Nintendo's Super Famicom, and perhaps on other platforms that preceded the Saturn. Where the Saturn does have trouble, is in the generation of these effects in a 3D environment. Along with lightsourcing, three dimensional transparency must be generated through software code. This is not a problem if the developer is familiar with writing Saturn software or was provided with the necessary programming libraries. For instance, Sega's "Sonic-R" features 3D transparency throughout the "Radiant Emerald" course, and lightsourcing can clearly be seen along the corridors of Lobotomy's "Powerslave" ("Exhumed" in the UK). Brian Osserman writes: "The situation with transparencies on the Saturn is exceedingly odd. The most common kind is via the background processor, which can more or less put two properly texture-mapped translucent perspective correct planes. This is what Panzer Zwei and Panzer Saga use for water, for instance. Beyond this, I don't remember the details, but Sonic R and Burning Rangers seem to use two different hacks to get non-dithered transparencies. I can't remember whether there are any other examples, though. I think these were cases of exceedingly clever programming, though, and it's no coincidence they were both late in the Saturn's lifetime." ----------------------------------------- The Saturn is equipped with dual custom VDP chips for graphics processing. The VDP 1 chip is primarily responsible for sprite generation. Polygon generation is accomplished through manipulation of the sprite engine. Texture mapping and goruard shading is also handled by the VDP 1. The VDP1 relies on a dual frame buffer that handles rotation and stores textures in special 512K cache. The VDP 2 serves as the Saturn's background processor. Certain special effects such as texture transparency and playfield rotation and scrolling (up to five fields at any given time) are handled here. Both VDP chips have direct access to the both SH2s, as well as direct memory access (DMA) to both the main and video RAM.

		antime		Jan 22, 2005
			The biggest inaccuracies in that text is the claim that 3D transparencies and lightsourcing would be software-only effects. As we know, VDP1 can do its own kind of transparencies and while the lightsourcing parameters must be calculated in software the actual effect can be accomplished using the hardware Gouraud shading capabilities (for flat shading you have more options). Also, the more or less legendary Sonic-R transparent course is just another example of VDP2 blending.

		Drenholm		Jan 22, 2005
			This is an interesting topic - I knew the Saturn was somewhat infamous for its lack of transparencies and cross hatching, but it's interesting to see so many different points and opinions on the topic. So basically, proper transparency can be accomplished using a combination of hardware and software methods? (goes to play Radiant Emerald )

		M3d10n		Jan 22, 2005
			Software-based transparency isn't feasible on the Saturn (or most of the systems), unless you're drawing everything using your own, super-optimized software renderer (anyone remember the Zyrinx 32X demo tape? Gouraud shading, additive blending and fog, all using custom renderers). It's just a matter of clever coding so the game makes use of the avaliable hardware transparency features while trying to avoid the limitations. Burning Rangers was the only game I know that went with major hacks to abuse the system features.

		Drenholm		Jan 22, 2005
			Thanks for the information, and congratulations on your Collapse and Braniac champion-dom!

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