forums.ps2dev.org

[Tinnus]

Does anyone know how the vf2in/vi2f functions work? Do they just convert a bunch of float values to int's/int's to float's, in the sense that after vf2in the VFPU regs now contain numbers coded like 32-bit signed int's instead of floats and I could then just store them back to memory and use as int's? Or in the case of vi2f I can just load int's into a VFPU register and that will convert them to floats?

If yes, that's SOOOOOOO great!!! :)
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Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[Raphael]

Yes.
There are also other vf2i versions for different rounding methods. Dunno exactly from the top of my head though.
_________________
<Don't push the river, it flows.>
http://wordpress.fx-world.org - my devblog
http://wiki.fx-world.org - VFPU documentation wiki
Alexander Berl

[Tinnus]

Thanks! :)

Now taking the opportunity, how do vmul/vdot/vdiv work? Do vmul and vdiv just multiply each part of the 2 vectors and put them at the respective place for the destination one? As for vdot, where does it put the result (since the dest reg is a vector)?

Also can the VFPU do Outer Products? If so, how?

Thanks in advance again :)
_________________
Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[Raphael]

[Tinnus]

Yes I mean the cross product. And thanks for clarifying the dot product destination register and all the rest :)
_________________
Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[Tinnus]

OK. Last question :)

I just found out you can put a scale value in vf2i and vi2f, but can't you use a negative scale? ie: like you were doing a shift to the right.

I tried but the assembler complained about "improper scale: some-big-number". I think he expects an unsigned value and got a big number since -12 in unsigned codification would turn out big.

Being able to scale down would be great for fixed-point...
_________________
Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[Raphael]

[Tinnus]

Because I'm working on emulating something that stores stuff internally as fixed-point.

Namely, one of the SNES coprocessors.

But that's not that big of a problem, I'll just do the >>'s in C after converting.
_________________
Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[Tinnus]

Just one more :)

Are there any instructions to move data to/from the general and VFPU registers? Or must I move data to memory first? (ugh)
_________________
Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[Raphael]

mtv $rs, $rd // move to vector, $rs -> $rd, $rs = mips register, $rd = single vfpu register
mfv $rd, $rs // move from vector, $rs -> $rd, $rd =mips register, $rs = single vfpu register
_________________
<Don't push the river, it flows.>
http://wordpress.fx-world.org - my devblog
http://wiki.fx-world.org - VFPU documentation wiki
Alexander Berl

[Tinnus]

Thanks again! :)

Now, do you know of any place I can get a *full* list of the VFPU ops? For example, none of the ones that I've seen until now have mfv/mtv/vcrsp/vim...
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Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[adrahil]

You could dig them out from here: http://svn.ps2dev.org/filedetails.php?repname=psp&path=%2Ftrunk%2Fbinutils-psp%2Fopcodes%2Fmips-opc.c&rev=0&sc=0

Look under the "/* Sony Allegrex VFPU instructions. */" section.

[Raphael]

[Tinnus]

Hmm, but how do I know what they do and what params they take?

Also any information on vcmp? I guess it does a comparison, but where is the result stored?
_________________
Let's see what the PSP reserves... well, I'd say anything is better than Palm OS.

[Raphael]

Some educated guessing plus try&error. I already thought about writing up all my findings so far to document the VFPU ops. Might be a good idea, but time-consuming.

vcmp stores the result of the compare in the cc (conditional register), which in turn can be checked on and branched with bc*f? (branch conditional* on false = if (!cc)) or bc*t? (branch conditional* on true = if (cc)) [I'm not sure what the possible l at the ? might mean]. There are versions for * = 0-3 (ie there are 4 conditional registers) but I'm yet to find out when exactly which one is used (I had luck with c1 in my current project).
The arguments of vcmp.* are CMP, rs, rd where CMP can be something like EQ (equals), LT/GT (lower/greater then), LE/GE (lower/greater or equal). rs and rd are single or vector registers, depending on * being .s or something else.
_________________
<Don't push the river, it flows.>
http://wordpress.fx-world.org - my devblog
http://wiki.fx-world.org - VFPU documentation wiki
Alexander Berl

[hlide]

[adrahil]

[hlide]

[Raphael]

[hlide]

Thanx Raphael !

Should I need to convert a 3D vector of fix point (1, 27, 4) to a 3D vector of float for some calculations, do :

[Raphael]

If you insist to store your vertices as ints (or are forced to), then you'd need to convert them yes, but I wouldn't recommend it. Better store everything as floats and work with them. Also note, that short/char vectors need an extra conversion step with vi2(u)s, vi2(u)c and reverse. Again, avoid those at any cost, it's ugly to work with them (but those conversions could come handy if you convert your internal models to non-float GU vertices for faster rendering).
_________________
<Don't push the river, it flows.>
http://wordpress.fx-world.org - my devblog
http://wiki.fx-world.org - VFPU documentation wiki
Alexander Berl

[hlide]

you're right, but as far as I know GTE (coprocessor 2 in PSX) use those kind of storage, so I was planning to use VFPU to emulate GTE.

[Raphael]