Liquid Simulation Display Options (GSoC 2020)

All the changes made in the branch `soc-2020-fluid-tools` are included in this patch.

**Major changes:**

=== Viewport Display ===

- //Raw voxel display// or //closest (nearest-neighbor)// interpolation for displaying the underlying voxel data of the simulation grids more clearly.
- An option to display //gridlines// when the slicing method is //single//.

==== Grid Display ====

- Visualization for flags, pressure and level-set representation grids with a fixed color coding based on Manta GUI.

==== Vector Display ====

- //**M**arker **A**nd **C**ell// grid visualization options for vector grids like velocity or external forces.
- Made vector display options available for external forces.

==== Coloring options for //gridlines// ====

- Range highlighting and cell filtering options for displaying the simulation grid data more precisely.
- Color gridlines with flags.

- Also, made slicing and interpolation options available for Volume Object.

Reviewed By: JacquesLucke, sebbas

Differential Revision: https://developer.blender.org/D8705

1 files changed, 25 insertions, 0 deletions

diff --git a/source/blender/makesdna/DNA_volume_types.h b/source/blender/makesdna/DNA_volume_types.h
index 30ac67281e2..bbd23298aea 100644
--- a/source/blender/makesdna/DNA_volume_types.h
+++ b/source/blender/makesdna/DNA_volume_types.h
@@ -38,6 +38,10 @@ typedef struct VolumeDisplay {
   float density;
   int wireframe_type;
   int wireframe_detail;
+  int interpolation_method;
+  int axis_slice_method;
+  int slice_axis;
+  float slice_depth;
   int _pad[1];
 } VolumeDisplay;
 
@@ -119,5 +123,26 @@ typedef enum VolumeRenderSpace {
   VOLUME_SPACE_WORLD = 1,
 } VolumeRenderSpace;
 
+/* VolumeDisplay.interpolation_method */
+typedef enum VolumeDisplayInterpMethod {
+  VOLUME_DISPLAY_INTERP_LINEAR = 0,
+  VOLUME_DISPLAY_INTERP_CUBIC = 1,
+  VOLUME_DISPLAY_INTERP_CLOSEST = 2,
+} VolumeDisplayInterpMethod;
+
+/* VolumeDisplay.axis_slice_method */
+typedef enum AxisAlignedSlicingMethod {
+  VOLUME_AXIS_SLICE_FULL = 0,
+  VOLUME_AXIS_SLICE_SINGLE = 1,
+} AxisAlignedSlicingMethod;
+
+/* VolumeDisplay.slice_axis */
+typedef enum SliceAxis {
+  VOLUME_SLICE_AXIS_AUTO = 0,
+  VOLUME_SLICE_AXIS_X = 1,
+  VOLUME_SLICE_AXIS_Y = 2,
+  VOLUME_SLICE_AXIS_Z = 3,
+} SliceAxis;
+
 /* Only one material supported currently. */
 #define VOLUME_MATERIAL_NR 1