[gameprogrammer] Re: Fixed point vs floating point in modern computers

  • From: Alan Wolfe <alan.wolfe@xxxxxxxxx>
  • To: gameprogrammer@xxxxxxxxxxxxx
  • Date: Fri, 24 Feb 2012 11:46:08 -0800

I don't really want to make my code have the requirement of needing shaders
at this point.

As it currently stands, i can run it on any device / machine that can
compile C++ and has a way for me to copy pixels to the display and find
that really attractive since i have a lot of lateral mobility (while
maintaining a single code base)

Not quite sure all of what I want to do with it yet and that lateral
mobility is really nice for me, and makes it easy to showcase the
techniques i came up with.

If i could use something like perhaps OpenCL and i could abstract it well
enough such that the same code worked on CPU and GPU, i'd be interested in
something like that, but i dont want to fork it or muddy the waters or
limit my options just yet.
2012/2/24 Stéphane Marchesin <stephane.marchesin@xxxxxxxxx>

> On Fri, Feb 24, 2012 at 11:29, Alan Wolfe <alan.wolfe@xxxxxxxxx> wrote:
> > "The trouble is that floating point implementations are a mess."
> >
> > That's what i'm hitting and it makes me sad hehe
> >
> > "1) be very careful about the stability of the numerical methods you use.
> > That is the best way to avoid problems cause by variations in precision."
> >
> > Agreed... I've investigated a little into this but so far no luck on
> finding
> > the problem.  I'm also making sure and be as "smart" as possible about
> the
> > math.  For instance as the ray walks through my world grid, I don't
> check if
> > the ray is between the beginning and end time (the time period of the ray
> > being inside the cell), i check that it's less than the end time since if
> > you are close enough to the edge of a cell, and use perhaps slightly
> > different equations for the start and end, you could have different
> values
> > and get into problems that way where an intersection fell between cells
> :P
> >
> > "So, maybe you should look at how to do all this in the GPU, rather that
> in
> > the CPU."
> >
> > That would be really awesome.  I would love to do that, but for the
> google
> > "Native Client" at least, they don't expose a way to do that which is
> kind
> > of sad.  I think you are right though, it might be really awesome to
> make it
> > able to run on the GPU with OpenCL or something just to see how much
> faster
> > it is (hopefully WAY fast)
> Why can't you use GLES2 for that? It's definitely possible to do
> raytracing in GLES2 with shaders, compute APIs are not required for
> that (you don't need the thread synchronization stuff for raytracing).
> Stéphane
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