Blender Git Loki

Minor sparse tile fixes.

Fixed some really obvious errors with CUDA sampling, and moved the
coordinates to index calculation back into kernel, saving a small
perecentage of time.

Updates to volume kernel tiling function.

1. OpenCL and CUDA support (mostly untested).
2. Change name of offsets to grid_info since it needs to keep track of
other info as well.
3. Several speed and memory optimizations.

Reduce sparse grid memory usage and minor fixes.

Sparse grids originally padded out an image to dimensions divisible by
TILE_SIZE, which resulted in many empty voxels in large volumes. Now,
border tiles are taken into account when calculating voxel indexes.

Aside from that, made some other minor fixes throughout the files.

Threshold sparse grid with volume mesh isovalue
and optimize tile copying during grid generation.

Remove SparseTile; support CPU tricubic interp.

Sparse grids now use their normal types instead of a specific struct.
Also added support for tricubic interpolation of sparse grids for CPU
rendering.

Added sparse grid lookup to mesh volume generator.

Also made some minor operator additions/changes.

Updates to tiling function.

1. Supports all data types (or at least the ones enumerated in
ImageDataType).

2. Will tile all volume attributes.

3. Changed method of activating tiling to a bool member of Image.

Created init functions for uchar4 and half4.

Initial working implementation of tiling for sparse grids.