On 20-1-2010 21:03, Nicolas Alvarez wrote:
> Warp wrote:
>> scott <sco### [at] scottcom> wrote:
>>>> Thank you.  I appreciate your open-mindedness.  I can perfectly accept
>>>> lack of human resources as a fine excuse, the others are just BS.

Nemesis: again, you are not qualified to judge that.

>>> I haven't really seen any valid *technical* reason why something like POV
>>> couldn't be ported to CUDA or OpenCL and run fine on the latest 3D cards.

Nemesis: no, you have not seen a reason that convinces you. That is not 
the same, given that you are not qualified to judge the technical merit.

>>> Most of the technical arguments against it are only valid for older cards
>>> (eg lack of double support, limits of number of instructions and
>>> branching etc).
>>   I repeat: If it's seemingly so easy, please go ahead and just do it.
>> All the material is there, ready to be put together. What are you waiting
>> for?
> 
> He didn't say it was easy, he said there is no reason why it would be 
> currently *impossible*.
> 
Nor did he say that it would be faster using a GPU. Only that all 
partial implementations are faster than POV.

It may be true that all requirements have been met individually (though 
I seriously doubt that, but that might take weeks to figure out given 
the large amount of research activity) and that there for there is no 
reason why the combination should be impossible in principle. To reach 
the goals shortcuts have been made and I am not in a position to judge 
if they are compatible. Experience tells me that the change that all 
optimizations are orthogonal is extremely small.
Just to find out if it is possible in principle would take another few 
weeks of dedicated study. After finding out that they can in principle 
be combined, figuring out if there is a way to do that that is still 
faster than a CPU is most probably months. And then it has to be 
implemented. When you reach the conclusion that it cannot be done within 
a week someone will come up with a new idea and you have to start all 
over again.
Given that most people here have only about a day per week max to devote 
to such a project, we are talking about several years of work with a 
high chance of failure. With a high change of starting all over before 
the project is finished because of new developments.
If you do this outside an academic environment or a lab of a big 
industry you don't stand a change.

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Warp escreveu:
>   However, the core renderer doesn't currently work that way. It doesn't
> "buffer" intersection tests to be calculated in a bunch and then processed
> all at the same time afterwards. It fully calculates one ray and all the
> new rays that it spawns before going to the next ray, and so on.

Curiously enough, it's the same basic process as a path tracer (like the 
one I linked to), except a path tracer spawns several times more rays 
for each ray than povray.

>   Even if you were able to totally change the design of the core renderer
> to do that, it would still probably help only in a limited amount of
> situations. Obviously it would only work with meshes (and perhaps some
> simple primitives such as spheres and planes), but ray-surface intersections
> are often *not* the heaviest part of the raytracing process. Texturing,
> lighting, media, photon mapping and radiosity often take a big chunk
> of the total time.

They take far less than a path tracer.

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

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andrel wrote:
> On 20-1-2010 21:03, Nicolas Alvarez wrote:
>> Warp wrote:
>>> scott <sco### [at] scottcom> wrote:
>>>> I haven't really seen any valid *technical* reason why something 
>>>> like POV
>>>> couldn't be ported to CUDA or OpenCL and run fine on the latest 3D 
>>>> cards.
> 
> Nemesis: no, you have not seen a reason that convinces you. That is not 
> the same, given that you are not qualified to judge the technical merit.

That's not me.

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>  I repeat: If it's seemingly so easy,

Where did I say it was easy?

> please go ahead and just do it.
> All the material is there, ready to be put together. What are you waiting
> for?

More time and programming skill.  Sorry but I don't have enough of it to 
give away for free.  I like tinkering on small apps but am not the sort of 
person who ever finishes things, so volunteering to do a huge project like 
this just seems ridiculous.

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On 21-1-2010 1:32, nemesis wrote:
> andrel wrote:
>> On 20-1-2010 21:03, Nicolas Alvarez wrote:
>>> Warp wrote:
>>>> scott <sco### [at] scottcom> wrote:
>>>>> I haven't really seen any valid *technical* reason why something 
>>>>> like POV
>>>>> couldn't be ported to CUDA or OpenCL and run fine on the latest 3D 
>>>>> cards.
>>
>> Nemesis: no, you have not seen a reason that convinces you. That is 
>> not the same, given that you are not qualified to judge the technical 
>> merit.
> 
> That's not me.

Sorry, misread the number of '>' I think you said something similar 
before, so I wrongfully assume it was you again.

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