Sabrina Kilian escreveu:
> nemesis wrote:
>> In any cases, you get it wrong:  the amazing speed up is not due to
>> native GPU triangle handling, but faster ray intersection calculations
>> thanks to the GPU sheer parallel vector processing.  You can see that in
>> smallptGPU where you get perfect math spheres much faster, no meshes in
>> sight.
>>
> 
> Spheres are the other special, easy, case. Any ray that comes within
> -radius- of -center point- must intersect the sphere, with a surface
> normal that is pretty easy to compute. From that, the diffuse,
> reflection, and so on. The math, as obvious by the very short
> intersection code in smallpt, is easy and compact.
> 
> Now, for any given cone, with arbitrary rotation and ratio of base to
> height, provide a fast general case for the ray intersection test, that
> will give you the same information. Single test, just to be clear, not
> separate cases for the disc bottom and cone top.
> 
> Then cube, then spline lathe, SOR, blobs . . .

It's an example that the speedup is independent of the native GPU 
triangle handling, nothing more.

I'm not math competent at all to give an answer to that.

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a game sig: http://tinyurl.com/d3rxz9

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>>> 3) Large memory sets (other than textures)
>> My GPU has access to just under 1GB of RAM. How much do you want?
>>
> 
> They lack virtual ram in a simple sense, last I looked, but you can
> manage that by having your CPU thread move things around as needed.
> Messy and annoying, when the CPU gives you just under 4 gigs in a simple
> 32-bit OS as long as the system has the virtual ram space available. And
> even more than that in 64-bit, if you ask the OS nicely. On the CPU,
> when you need different parts of that 4 gigs of stuff, the OS handles
> it. I suspect that, should the GPU need new data fed into memory, it
> would require more than just stalling the threads while the data is
> moved from ram or paged memory over to the graphics card.

You people must render something utterly different to what I render! I 
think the most demanding scene I ever ran wanted 10MB of RAM or something...

>>> 4) Independent shaders running on distinct units.
>> What exactly do you mean by that?
> 
> I am guessing that he meant the ability to run multiple threads on the
> GPU, instead of running 100 instances of the same thread with slightly
> different starting conditions. I know that my card supports 4 different
> work groups, split over 8 'processors' each.

The information I got is that the GPU runs "bunches" of threads on its 
several-hundred cores, and all the threads in a "bunch" must be 
identical [just operating on different data], but different bunches can 
run utterly different code...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Orchid XP v8 wrote:
> You people must render something utterly different to what I render! I
> think the most demanding scene I ever ran wanted 10MB of RAM or
> something...
> 

I was wrapping an object in wire using a sphere sweep. While it was just
a minor background detail, I had several billion spheres. In my defense,
I was also doing this just to find the point at which I ran out of memory.

>>>> 4) Independent shaders running on distinct units.
>>> What exactly do you mean by that?
>>
>> I am guessing that he meant the ability to run multiple threads on the
>> GPU, instead of running 100 instances of the same thread with slightly
>> different starting conditions. I know that my card supports 4 different
>> work groups, split over 8 'processors' each.
> 
> The information I got is that the GPU runs "bunches" of threads on its
> several-hundred cores, and all the threads in a "bunch" must be
> identical [just operating on different data], but different bunches can
> run utterly different code...
> 

In general, though, what is the smallest maximum number of "bunches"
that you can run? I know my card lists 4 work groups, I do not know if
any other cards currently being sold only allow 2, or possibly only 1,
bunch to be run at once.

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Orchid XP v8 escreveu:
> You people must render something utterly different to what I render! I 
> think the most demanding scene I ever ran wanted 10MB of RAM or 
> something...

I'm sure even a game like Crysis needs more memory than your pov RSOCPs.

-- 
a game sig: http://tinyurl.com/d3rxz9

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>> The information I got is that the GPU runs "bunches" of threads on its
>> several-hundred cores, and all the threads in a "bunch" must be
>> identical [just operating on different data], but different bunches can
>> run utterly different code...
>>
> 
> In general, though, what is the smallest maximum number of "bunches"
> that you can run? I know my card lists 4 work groups, I do not know if
> any other cards currently being sold only allow 2, or possibly only 1,
> bunch to be run at once.

I'll check the CUDA manual. Obviously this stuff varies by GPU, but I 
was under the impression my card handles something like 16 bunches at 
once or so.

Certainly you can't currently run thousands of seperate tasks at once. 
But then, my card (for example) has something like 300 hardware units. 
That's a hell of a lot more than 4 CPU cores...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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>> You people must render something utterly different to what I render! I 
>> think the most demanding scene I ever ran wanted 10MB of RAM or 
>> something...
> 
> I'm sure even a game like Crysis needs more memory than your pov RSOCPs.

Crysis represents complex shapes by just blindly throwing hundreds of 
billions of triangles at the problem.

Also, Crysis has to represent an entire world, not just the image 
currently on screen.

Finally, Crysis was made by people who actually possess talent. :-(

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Sabrina Kilian wrote:
> Messy and annoying, when the CPU gives you just under 4 gigs in a simple
> 32-bit OS as long as the system has the virtual ram space available. And
> even more than that in 64-bit, if you ask the OS nicely. 

More than that in 32 bits too, if you ask the OS nicely. :-) You just have 
to manage the virtual -> real mapping yourself.  (I.e., the mapping of your 
virtual addresses onto disk space, not the mapping of your virtual addresses 
into RAM space.)

People nowadays don't remember what it was like when *every* program didn't 
have enough address space, when a simple sub-notepad-sophistication keyboard 
driven text editor didn't have enough address space to hold a document...

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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Darren New <dne### [at] sanrrcom> wrote:
> People nowadays don't remember what it was like when *every* program didn't 
> have enough address space, when a simple sub-notepad-sophistication keyboard 
> driven text editor didn't have enough address space to hold a document...

  Good thing that technology marches forward, isn't it?-)

-- 
                                                          - Warp

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Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> People nowadays don't remember what it was like when *every* program didn't 
>> have enough address space, when a simple sub-notepad-sophistication keyboard 
>> driven text editor didn't have enough address space to hold a document...
> 
>   Good thing that technology marches forward, isn't it?-)

Indeed. It's nice to be able to tell the customer it's now *his* fault when 
his files are too big. ;-)

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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Orchid XP v8 escreveu:
>>> You people must render something utterly different to what I render! 
>>> I think the most demanding scene I ever ran wanted 10MB of RAM or 
>>> something...
>>
>> I'm sure even a game like Crysis needs more memory than your pov RSOCPs.
> 
> Crysis represents complex shapes by just blindly throwing hundreds of 
> billions of triangles at the problem.

yes, which is why it needs so much memory.

-- 
a game sig: http://tinyurl.com/d3rxz9

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