One TMU every two pipes and writing to texture on PS2?

[MrWibble]

Of course if you really want two front buffers, you can do that too, as the PS2 has a dual-circuit display system...

Interesting...does that mean you can set up a dual display dealie, given the proper cabling?


Also, the complaint about GS not having any native clipping seems kinda silly to me, seeing as how clipping works on 3D-space geometry before it's converted to a 2D raster on the GS. Isn't this typically done on the CPU by the developer for video hardware that doesn't have T&L?

I believe the GS would be capable of two display outputs, but the rest of the hardware isn't geared up for it, and so the only thing you can do is combine the two display outputs into a single display.

And if I had to clip on the CPU I probably wouldn't complain - the pain comes from it having to be done on VU1 at the end-stage of the transform pipe... it's just annoying having to have either clipped and non-clipped versions of all your code, or having to come up with some kind of generalised (and possibly slower) system to use a standard clipper for all your code-paths. Either way it'd make life a whole lot easier to have the clip done at the GS end...

 

[darkblu]

Also, the complaint about GS not having any native clipping seems kinda silly to me, seeing as how clipping works on 3D-space geometry before it's converted to a 2D raster on the GS. Isn't this typically done on the CPU by the developer for video hardware that doesn't have T&L?

you've got it right. when vertices reach the rasteriser they are supposed to have all components screen-space correct (and that holds for all rasteriser hardware i've come across). the reason for this is not that a 3d rasteriser could not perform planar clipping on geometry - it could if it wanted to, but in screen space it's kinda hard to devise a sound criterion for 'depth goodness'. latter comes from the fact that a rasteriser is subject to homogeneous space sigularities coming from homogeneous space, due to the W (aka RHW) component of the geometric data used in "perspective-correction" division operations. that's why before reaching the rasterisation stage, vertex data is made sure to be clipped in some near-to-far depth bounds, satisfying along other things, a division-safe RHW component. still, a 3d rasteriser often does scissoring, or guardband clipping.

 

[JesusClownFox]

And if I had to clip on the CPU I probably wouldn't complain - the pain comes from it having to be done on VU1 at the end-stage of the transform pipe... it's just annoying having to have either clipped and non-clipped versions of all your code, or having to come up with some kind of generalised (and possibly slower) system to use a standard clipper for all your code-paths. Either way it'd make life a whole lot easier to have the clip done at the GS end...

I thought clipping and culling was always the end-stage of the transform pipe. It seems that you're looking at this issue from a multiplatform point of view, if that's what you mean by separate "clipped" and "non-clipped" versions.

 

[Crazyace]

With PS2 the vector unit is the Transform/Clipping/Lighting part of the pipeline - but you have to write the code yourself ( or use the samples ) and if you know that your meshes are onscreen you can save time by not implementing clipping at all.
Effectively you have the same geometry data, but 2 programs to process it which are selected each frame.

 

[JesusClownFox]

So MrWibble was referring to the tediousness of alternating between clipped or non-clipped algorithms for different situations in-game? I guess that's what you mean by two programs, yes?

 

[MrWibble]

So MrWibble was referring to the tediousness of alternating between clipped or non-clipped algorithms for different situations in-game? I guess that's what you mean by two programs, yes?

Switching between paths isn't too tedious - having to *write* two paths for everything can be. Especially when you're doing anything complicated and you're running out of space in that 16k...

It's not like it's a show-stopper or anything, it's just one of those annoying things you get used to...