I was about to ask why we aren't just using the log2 function here, but
apparently Microsoft doesn't consider this C99-standard function to be
important (ie: it's not included in Microsoft's math.h).
Seems like cmath is indeed the best solution.
--"J"
On 01/09/2013 11:39 AM, Christian Schulte wrote:
Hi Robert,
I think the problem is linked indeed to a MS math.h problem, but in my
opinion it is not linked directly to the floor function but could affect
even other functions. I don't know what would be the consequences on the
global OSG behaviour but I agree with you that replacing the math.h
include would be the best solution.
Maybe someone could try to compile my little test code with a Microsoft
compiler to see if it is gcc linked or Windows linked.
Cheers,
Christian
Le 09/01/2013 16:50, Robert Osfield a écrit :
Hi Christian,
Does this mean there is a bug in the MS version of math.h and the
floor function it provides?
Previously we haven't used cmath as some platforms didn't support it
properly, I recall IRIX being a problem, but am not sure if it extends
further than this. IRIX support has long been deprecated so won't be
a constraint these days. So... using #include<cmath> could well be a
viable solution,
It does still concern me that the MS version of math.h is giving
different results to cmath.
Robert.
On 9 January 2013 15:27, Christian Schulte<[email protected]> wrote:
Hi all,
I have investigated a little deeper the problem... Indeed, on Windows
platform, the number of mipmaps returned by
osg::Image::computeNumberOfMipmapLevels( s, t, r ) is wrong, but it is
correct on Linux platforms for the same dds file...
Here is attached a little test program that explains why (it is more or less
a computeNumberOfMipmapLevels with s=t=1024 and r=1), and it is not linked
to OSG. Compile it on Windows 32 bits (works on Win7 and WinXP) (g++
main.cpp -o main.exe) You will see the following result :
logf(wf) = 6.93147182464599609375
log(wd) = 6.93147180559945308431
logf(2.0f) = 0.69314718246459960938
log(2.0) = 0.69314718055994528623
logf(wf)/logf(2.0f) = 10.00000000000000000000
log(wd)/log(2.0) = 10.00000000000000000000
floor(logf(wf)/logf(2.0f)) = 9.00000000000000000000 -> Here is the error, it
should be 10 too...
floor(log(wd)/log(2.0)) = 10.00000000000000000000
floor(testf) = 10.00000000000000000000
floor(testd) = 10.00000000000000000000
Replacing the include of math.h by cmath results in :
logf(wf) = 6.93147182464599609375
log(wd) = 6.93147180559945308431
logf(2.0f) = 0.69314718246459960938
log(2.0) = 0.69314718055994528623
logf(wf)/logf(2.0f) = 10.00000000000000000000
log(wd)/log(2.0) = 10.00000000000000000000
floor(logf(wf)/logf(2.0f)) = 10.00000000000000000000
floor(log(wd)/log(2.0)) = 10.00000000000000000000
floor(testf) = 10.00000000000000000000
floor(testd) = 10.00000000000000000000
Under Linux both solutions give the second results.
The problem is that osg/Math includes math.h and not cmath. I don't know
which would be the best solution :
Replace math.h by cmath in include/osg/Math
Store the logf division (float testf = logf(wf)/logf(2.0f)) of
osg::Image::computeNumberOfMipmapLevels( s, t, r ) in a float before
computing the floor.
Up to the list to give the answer...
PS : this is also the solution to the discussion "osgPlugins : dds problem
on windows platform" I launched 07/03/2011
Cheers,
Christian Schulte
Le 20/12/2012 15:15, Lukasz Izdebski a écrit :
Hi,
i probably have solution for this problem, i have found a bug in dds plugin
ReaderWriterDDS.cpp
Line 633
unsigned numMipmaps = osg::Image::computeNumberOfMipmapLevels( s, t, r );
when compute numMipmaps returns wrong number. this number is less then
number of mipmaps in dds file( ddsd.dwMipMapCount ) . This bug makes that
when dds mipmaps are loaded to opengl last mipmap (4x4) isn't loaded. and
with combination with LINEAR_MIPMAP_LINEAR make this bug.
the numMipmaps should be taken form ddsd.dwMipMapCount
in attachment i send a corrected version of file.
...
Thank you!
Cheers,
Lukasz
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=51653#51653
Attachments:
http://forum.openscenegraph.org//files/readerwriterdds_204.cpp
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