Remove OpenEXR library dependency.

[syoyo]

Please consider to use tinyexr, embeddable OpenEXR image loader into PBRTv2(or maybe v3?).

https://github.com/syoyo/tinyexr

I saw many PBRT beginner struggle to build and link ILM's OpenEXR library into PBRT, before they actually start to use/hack PBRT.

tinyexr will solve such a problem and users can concentrate on doing light transport using PBRT. It seems tinyexr already has enough features to replace ILM's OpenEXR lib(writing EXR image is not yet, but you can use miniexr https://github.com/aras-p/miniexr )

[mmp]

I was already planning on trying it for v3 (with Aras's EXR writer). :-)

I definitely agree that having to build OpenEXR is a big bother for people who just want to get started using pbrt, so my basic plan is to adopt those and try to make that work.

It's probably worth trying this soon for v2, to make it easier before v3 comes out.

[syoyo]

Cool!

Let me know if you find any missing features in tinyexr. I'll try to implement it.

[mmp]

Fixed in v3 by including openexr in the cmake build; will not fix for v2 at this point.