0 is incorrectly considered a power of 2 in function IsPowerOf2
Fix bug in GonioPhotometricLight::Scale() method.

The SPECTRUM_ILLUMINANT enum was being passed to MIPMap::Lookup()
rather than to the Spectrum() constructor!  This in turn caused
the lookup method to do a wide trilinear filter, thus basically
completely breaking gontiophotometric lights.
Fix bug in filename handling in dipole subsurface renderer.

Previously, we were using ParamSet::FindOneString() to get the
filename from the parameters; we should have been using
FindOneFilename(); this in turn led to a case where if you rendered
pbrt-scenes/ballpile.pbrt from a different directory, the
"surfacepoints.out" file would be written to the directory that
ballpile.pbrt was in, but then it wouldn't be found by the
DipoleSubsurfaceIntegrator when it went to render the scene..
fix rare error where make clobbers needed intermediate files (Zach Devito)
Fix naming of variable to be consistent with derivation
Fix bug in AnimatedTransform::MotionBounds (Yunjian Ding)
Merge branch 'master' of github.com:mmp/pbrt-v2
Merge branch 'master' of ssh://home/Users/mmp/git/pbrt
Fix formatting in error strings for negative/infinite luminances.
add src/build to gitignore

Signed-off-by: liuhuahang <liuhuahang@xiaomi.com>
Fix accel.d dtrace script
Make a copy of a filename passed to DirectoryContaining()

According to IEEE Std 1003.1, dirname() MAY modify the received value.
http://pubs.opengroup.org/onlinepubs/009604599/functions/dirname.html
Merge pull request #18 from steelman/for-mmp

Make a copy of a filename passed to DirectoryContaining()
Merge pull request #15 from huahang/master

add src/build to gitignore
Merge pull request #12 from GraphicsMe/master

0 is incorrectly considered a power of 2 in function IsPowerOf2
Add flag to silence slew of compiler warnings on OSX 10.9
Add #error directive if g++ 4.8.2 is used (Thanks @BachiLi!)
Merge branch 'master' of github.com:mmp/pbrt-v2
Fix bug in transformation of dndu and dndv in Triangle::GetShadingGeometry.

These should be transformed by the passed-in obj2world transformation, not
by *ObjectToWorld stored in the Shape.

Reported by Yunjian Ding.
Add missing cosine term in IGI light path tracing.

Reported by bachi722@gmail.com.