Blender Git Loki

Correct UI names and tooltips.

Add a dedicated poll function for the cache operators.

Cleanups:

- automatically add an underscore to the filename before the frame
number in the filename instead.
- rename "string" -> "r_filename" argument
- removed useless NULL check

Ask user to overwrite files if they already exist.

Only checks for the frame though.

Fix for recent clip change: ensure fluid matrices are computed for the
export.

Ensure cache directory exists.

Clip some low res grids based on the high res density.

Rationale is that in some cases the high resolution density is larger
than the low resolution one, so here we ensure there's enough data for
lookup during rendering for instance.

Decrease tolerance for vector grids due to possible loss of data.

Increase tolerance value used for copying a dense array to a sparse
grid.

This doesn't affect low resolution grids much but makes a real
difference for high res grids, as it only considers values real close to
the actual smoke or fire.

Although it might be a bit high of a value, it gives some nice file
sizes going from 106.6 Mb down to 37.7 Mb (pointcache: 264.3 Mb) in a
simple simulation with a base res of 128 and a high res of 2.

Merge branch 'master' into openvdb

Cycles: first pass at using VDB ray intersectors for ray marching.

The idea behind them is to avoid unnecessary ray marching by frog
leaping empty space. The only requirement for it to work is to have a
grid whose voxels are uniform, otherwise Cycles' default ray marching is
used.

For now the code has a some issues and dark sides to it:
- it only works if there is a single object containing vdb volumes in
the scene
- for a given file, only the grid named "density" (case insensitive) is
used for intersection, it's not clear how to handle multiple grids in
this case (maybe we coiuld let the user set which one to use?)
- the ray march loop is a total duplicate of the default one, this will
be addressed later on
- some leaf nodes are missing when using large volumes, the issue might
be the early exit due to the check to see if light was totally absorbed
or not

Here's some render tests:
Dense volume: http://www.pasteall.org/pic/89090
VDB with intersection: http://www.pasteall.org/pic/89092

Use multithreading when doing an export.

Fix grid clipping resulting in empty trees.

Issue was that the grids didn't have a transform set when clipping was
happening. As the clip operator copies the transform (here an invalid
one) from the grid to the mask if their tranforms mismatch, the
operation resulted in an invalid/empty tree.

(Best explanation I can give so far.)

Also for some reason exporting the obstacles field doesn't work anymore,
so it is disabled for now, and so is clipping for it as it doesn't make
sense to clip the obstacles based on the density field.

Draw a voxel in the viewport along with the smoke domain.

This helps a bit choosing a good resolution. Might be for development/
debug only, but it wouldn't hurt leaving it to help users.

Do not show fps while scrubbing.

Do not store frame change in undo stack (causes much waiting for
animators in heavy scenes)

Merge branch 'master' into gooseberry

Fixed incorrect macro for testing build settings.

Indicator for the player (togglable with I key).

Draws a green line where the current frame is in the movie.

Collapsed images:

* Icon of collapsed images is same as a movie
* Size displayed is cummulative size of all images
* Frame range is displayed in the filename