Shaders
Many news in material shaders, plus lots of updates, fixes, improvements.
Major news:
- diffuse/reflective/plastic material transparency handled with alpha channel of textures
- scatterng and light emission in volumes: support enabled in background modes AmbientAndVolume, TextureFixed, and TextureEnvironment;
subsurface color added to material parameters - load multiple meshes from .obj with materials specified in a dictionary, and an option to select parent mesh (then transormations of parent are applied to children meshes as well)
- setup parallelogram light using center/target 3D points and scalar lengths of u/v sides
- method to select objects for manual manipulation in gui (if e.g. cannot click object invisible in the view)
- keep_on_host argument of load_displacement() and load_normal_tilt() removed (value always set to false now; it was a bug in linux).