Also compute RMS error in exrdiff
Silence compiler warning
Remove unused jitterSamples member variable from RandomSampler
Create a NULL bump map when none is specified, rather than a constant texture with value zero
Fix handling of no bump map in glass material as well
Fix crashes when measured BRDF file or Included pbrt scene file aren't found.

Changed a number of usages of Severe() (which should only be used for really bad
unexpected logic errors in pbrt, not regular error cases like missing files) to
Error() and then a call to exit() so that we don't get a call to abort() on the
way out for those.
Fix bug in ImageFilm::GetSampleExtent() 

(Reported by Christian Lessig).

When the fractional component of the filter function's width is exactly
0.5, this function would end up requesting an unnecessary row and column
of samples along the edges of the image.  This is now fixed.
Add missing world to volume transformation in HomogeneousVolumeDensity::tau
Revert "Add missing world to volume transformation in HomogeneousVolumeDensity::tau"

This reverts commit 73ca02e21b58e870b3e7da3e8451e0736f3036a0.

This transformation is applied in the end by the call to
HomogeneousVolumeDensity::IntersectP.
Fix bugs in Russian roulette tests in volume integrators.

When we terminate a ray in the RR test that kicks in once opacity gets
close to one, we also need to set its transmittance to zero, so that none
of the background is visible along the ray.  (This is necessary to
counterbalance the effect of transmittance being reduced for the rays
that don't pass the RR culling.)
Fix Windows and Linux build
Merge pull request #11 from ericmj/master

Fix Windows and Linux build
Windows 7 build fixes.

If it exists, delete pbrtparse.hh before renaming pbrtparse.hpp to .hh.
Update syntax of 'ren' command to work on Windows 7.
Fix use of precompiled headers for MSVC 2010 builds.
Fix VS2008 makefile for Windows 7 "ren" command issues.
Improve reporting of error messages.

Now, we build up the entire message into a std::string and print it with a single
call to fprintf(); this way, if multiple threads are printing errors/warnings
simultaneously, the results won't be jumbled and intermingled.

(fprintf prints its output atomically, while a set of calls to fputc, which we had
before, didn't give us that..)
Return true from Quadratic() when there's a single intersection (Srinath Ravichandiran).

Previously, we returned false in this case.
Fix some Materials to not add black BxDF components.

Bug 111.
Small fixes to fix build with C++11 compilers.