All textures are sampled bi-linear currently with the exception of OSL there texture sampling is fixed and set to smart bi-cubic. This patch adds user control to this setting. Added: - bits to DNA / RNA in the form of an enum for supporting multiple interpolations types - changes to the image texture node drawing code ( add enum) - to ImageManager (this needs to know to allocate second texture when interpolation type is different) - to node compiler (pass on interpolation type) - to device tex_alloc this also needs to get the concept of multiple interpolation types - implementation for doing non interpolated lookup for cuda and cpu - implementation where we pass this along to osl ( this makes OSL also do linear untill I add smartcubic to the interface / DNA/ RNA) Reviewers: brecht, dingto Reviewed By: brecht CC: dingto, venomgfx Differential Revision: https://developer.blender.org/D317