On Tuesday 01 February 2005 14:37, Timothy Miller wrote:
Daniel Phillips wrote:
On Tuesday 01 February 2005 13:55, Timothy Miller wrote:
Correct me if I'm wrong, but "normalized device coordinates" have been projected but not scaled, right?
Rotated and projected so that all view planes are orthogonal, and scaled to [-1, +1] in all dimensions I think.
I wasn't sure if negative Z's were allowed or not.
They're not, I slipped there, it's been a couple years.
No problem. :)
My guess is that in a perfect world we should round down, but saving a few gates is enough excuse for rounding up. Fortunately it's a FPGA, so there's hardly any penalty for guessing wrong the first time.
Your GUESS? Is there anything which states it definitively?
I'm waiting for an OpenGL lawyer out there to speak up. I know they're lurking ;-)
What we need is someone who's a core Mesa member.
That would be Brian Paul, but he's a pretty busy guy, maintaining Mesa almost single handedly as he does, so I would recommend studying the terminology a little more from public sources before bringing such questions up on the mesa lists.
It's understandable. More important than terminology is just getting the math right. :)
There are certain big-wigs who seem to be keeping their distance.
I wouldn't read anything into that. It's mostly a matter of information dissemination. The thing is, it's a lot easier to disseminate information after everybody is on the same page than before. Certain big-wigs have already been contacted, and for your information, nobody has said it's all a really stupid idea, quite the contrary in fact. Prototype hardware is wanted.
I understand, and thank you.
Notice that RMS and ESR are silent.
As should anybody who doesn't know anything about 3D graphics.
Oh, I don't mean on the subject of 3D graphics but on the connection with Free Software.
If this project succeeds, it'll open up a lot more interest in other companies to support free software.
Keith Packard hasn't said anything either, to my knowledge. Linus stayed out of the conversation on LKML.
No big deal and no need to worry about it. I suspect Linus will get on board when you send him a card to play with that works in some fashion.
Yes, as I mentioned in the interview, many people aren't all that interested until they have hardware in their hands. It's hard to stay excited for long periods about an abstract idea. (Well, I do, but I'm weird. :)
Alan Cox, I think, was very receptive to it, and there are other kernel contributors who want to help. (But who don't have time to be on another mailing list.)
After all, it's more fun than messing with memory management all the time, and Andrew Morton does that these days anyway. DRI guys will probably get on board when they get cards that don't even work very well. Other hardware guys will get interested as soon as the DMA specs are nailed down (because they want to review them).
Yeah. I'm concerned that I'll do something half-right or completely wrong but not find out until it's too late.
That is for sure the right thing to do. Y should be fixed point too, IMHO.
Y is integer. The software is responsible for adjusting all other parameters to be correct. See the model source for how that is done.
I meant, before being converted to pixel coordinates.
Right. That's done in the host, so I assume it'll always be in float. To the hardware Y is ALWAYS an integer.
In the future, when we have a geometry engine, things will change.
BTW, how do you do "0.5 rounds down" in software? Quick and dirty rounding function is floor(x+0.5) which rounds UP for 0.5. Is there a simple way to do it in software? ceil(x-0.5) ???
Of course. High level programming guys don't care a wit that there's an extra test involved.
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