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Re: passing static 2D array to function - not fully working like I hoped for...

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Jens Thoms Toerring於 2011年12月30日星期五UTC+8上午3時38分38秒寫道：
> someone <news...@gmail.com> wrote:
> > On Dec 29, 6:34 pm, j....@toerring.de (Jens Thoms Toerring) wrote:
> > > someone <news...@gmail.com> wrote:
> > >
> > > Please note that your code is C++ while this is a C newsgroup.
> 
> > Maybe 1% C++ and 99% C, ok.
> 
> Well, there are sume subtle differences between C and C++
> and when you write C++ (i.e. use a C++ compiler, your program
> won't compile with a C compiler) then it's typically better
> to ask in the correct group - it may safe you a lot of time
> and grieve. And sometimes there are also more elegant so-
> lutions to a problem in C++.
> 
> > > Note that the casts to 'GLfloat' are rather likely unnecessary
> > > - why did you put them in? I would recomend to use casts only
> 
> > Actually I cast double -> float, so I make the intermediate
> > calculations using double precision, but when it comes to actually
> > storing the data, I save it as a float (less precision). Normally I
> > would be doing everything with double precision...
> 
> All calculations are done in double anyway (even if you
> use floats - and on quite a number of architectures even
> with an even wider representation than double, i.e. on
> x86 you often have 64 bit doubles but computation are all
> done with 80 bit) and if you assign to a float the value
> will be converted to a float without any cast.
> 

A float can fit in 32 bits. The lifting of two floats into  doubles of 64 or 
 80 bits either does not increase the  precisions of the two sources at all 
in any math operations but can save the result better than a float.




 


> > Of some reason, floats seem to be widely used with opengl...
> 
> Probably because the results don't need a high precision (does
> it matter if a pixel is shown at position 231.122387267423 or
> 231.122387267424?) and floats often take only half as much
> space as doubles to store.
>                              Regards, Jens
> -- 
>   \   Jens Thoms Toerring  ___      j...@toerring.de
>    \__________________________      http://toerring.de

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passing static 2D array to function - not fully working like I hoped for... someone <newsboost@gmail.com> - 2011-12-29 09:11 -0800
  Re: passing static 2D array to function - not fully working like I hoped for... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-29 17:27 +0000
    Re: passing static 2D array to function - not fully working like I hoped for... someone <newsboost@gmail.com> - 2011-12-29 10:55 -0800
  Re: passing static 2D array to function - not fully working like I hoped for... jt@toerring.de (Jens Thoms Toerring) - 2011-12-29 17:34 +0000
    Re: passing static 2D array to function - not fully working like I hoped for... someone <newsboost@gmail.com> - 2011-12-29 11:03 -0800
      Re: passing static 2D array to function - not fully working like I hoped for... jt@toerring.de (Jens Thoms Toerring) - 2011-12-29 19:38 +0000
        Re: passing static 2D array to function - not fully working like I hoped for... "BartC" <bc@freeuk.com> - 2011-12-29 23:19 +0000
          Re: passing static 2D array to function - not fully working like I hoped for... "BartC" <bc@freeuk.com> - 2011-12-31 11:29 +0000
        Re: passing static 2D array to function - not fully working like I hoped for... 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 17:26 -0800
      Re: passing static 2D array to function - not fully working like I hoped for... Keith Thompson <kst-u@mib.org> - 2011-12-29 11:58 -0800
        Re: passing static 2D array to function - not fully working like I hoped for... Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 17:45 -0800
          Re: passing static 2D array to function - not fully working like I hoped for... Kaz Kylheku <kaz@kylheku.com> - 2012-01-26 02:08 +0000
      Re: passing static 2D array to function - not fully working like I hoped for... James Kuyper <jameskuyper@verizon.net> - 2011-12-29 15:35 -0500
        Re: passing static 2D array to function - not fully working like I hoped for... Keith Thompson <kst-u@mib.org> - 2011-12-29 13:25 -0800
          Re: passing static 2D array to function - not fully working like I hoped for... "io_x" <a@b.c.invalid> - 2011-12-31 16:32 +0100
            Re: passing static 2D array to function - not fully working like I hoped for... 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-31 15:10 -0800
              Re: passing static 2D array to function - not fully working like I hoped for... "osmium" <r124c4u102@comcast.net> - 2011-12-31 18:03 -0600
      Re: passing static 2D array to function - not fully working like I hoped for... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-29 20:37 +0000
        Re: passing static 2D array to function - not fully working like I hoped for... jgk@panix.com (Joe keane) - 2012-01-03 15:48 +0000
          Re: passing static 2D array to function - not fully working like I hoped for... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-03 16:47 +0000
          Re: passing static 2D array to function - not fully working like I hoped for... Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-01-05 22:31 +0200
      Re: passing static 2D array to function - not fully working like I hoped for... Nobody <nobody@nowhere.com> - 2011-12-31 09:23 +0000
        Re: passing static 2D array to function - not fully working like I hoped for... Keith Thompson <kst-u@mib.org> - 2011-12-31 11:04 -0800
          Re: passing static 2D array to function - not fully working like I hoped for... Nobody <nobody@nowhere.com> - 2012-01-01 08:20 +0000
  Re: passing static 2D array to function - not fully working like I hoped for... Barry Schwarz <schwarzb@dqel.com> - 2011-12-29 09:49 -0800
    Re: passing static 2D array to function - not fully working like I hoped for... someone <newsboost@gmail.com> - 2011-12-29 11:13 -0800
      Re: passing static 2D array to function - not fully working like I hoped for... Seebs <usenet-nospam@seebs.net> - 2011-12-29 19:22 +0000
        Re: passing static 2D array to function - not fully working like I hoped for... someone <newsboost@gmail.com> - 2011-12-29 13:29 -0800
          Re: passing static 2D array to function - not fully working like I hoped for... Seebs <usenet-nospam@seebs.net> - 2011-12-29 21:42 +0000
            Re: passing static 2D array to function - not fully working like I hoped for... someone <newsboost@gmail.com> - 2011-12-29 15:28 -0800
          Re: passing static 2D array to function - not fully working like I hoped for... Keith Thompson <kst-u@mib.org> - 2011-12-29 14:46 -0800
        Re: passing static 2D array to function - not fully working like I hoped for... James Kuyper <jameskuyper@verizon.net> - 2011-12-29 18:29 -0500
          Re: passing static 2D array to function - not fully working like I hoped for... Seebs <usenet-nospam@seebs.net> - 2011-12-30 00:03 +0000
            Re: passing static 2D array to function - not fully working like I hoped for... James Kuyper <jameskuyper@verizon.net> - 2011-12-29 21:30 -0500
        Re: passing static 2D array to function - not fully working like I hoped for... Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 17:47 -0800
  Re: passing static 2D array to function - not fully working like I hoped for... Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-25 17:39 -0800

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