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

3 files changed, 87 insertions, 16 deletions

diff --git a/source/blender/makesdna/DNA_fluid_types.h b/source/blender/makesdna/DNA_fluid_types.h
index 6035c43ad57..8e7f3471e1e 100644
--- a/source/blender/makesdna/DNA_fluid_types.h
+++ b/source/blender/makesdna/DNA_fluid_types.h
@@ -66,12 +66,6 @@ enum {
   FLUID_DOMAIN_FILE_BIN_OBJECT = (1 << 4),
 };
 
-/* Slice method. */
-enum {
-  FLUID_DOMAIN_SLICE_VIEW_ALIGNED = 0,
-  FLUID_DOMAIN_SLICE_AXIS_ALIGNED = 1,
-};
-
 /* Axis aligned method. */
 enum {
   AXIS_SLICE_FULL = 0,
@@ -86,17 +80,32 @@ enum {
   SLICE_AXIS_Z = 3,
 };
 
-/* Axis aligned method. */
-enum {
-  VOLUME_INTERP_LINEAR = 0,
-  VOLUME_INTERP_CUBIC = 1,
-};
+/* Display interpolation method. */
+typedef enum FLUID_DisplayInterpolationMethod {
+  FLUID_DISPLAY_INTERP_LINEAR = 0,
+  FLUID_DISPLAY_INTERP_CUBIC = 1,
+  FLUID_DISPLAY_INTERP_CLOSEST = 2,
+} FLUID_DisplayInterpolationMethod;
 
 enum {
   VECTOR_DRAW_NEEDLE = 0,
   VECTOR_DRAW_STREAMLINE = 1,
+  VECTOR_DRAW_MAC = 2,
+};
+
+enum {
+  VECTOR_DRAW_MAC_X = (1 << 0),
+  VECTOR_DRAW_MAC_Y = (1 << 1),
+  VECTOR_DRAW_MAC_Z = (1 << 2),
 };
 
+/* Fluid domain vector fields. */
+typedef enum FLUID_DisplayVectorField {
+  FLUID_DOMAIN_VECTOR_FIELD_VELOCITY = 0,
+  FLUID_DOMAIN_VECTOR_FIELD_GUIDE_VELOCITY = 1,
+  FLUID_DOMAIN_VECTOR_FIELD_FORCE = 2,
+} FLUID_DisplayVectorField;
+
 enum {
   SNDPARTICLE_BOUNDARY_DELETE = 0,
   SNDPARTICLE_BOUNDARY_PUSHOUT = 1,
@@ -125,6 +134,28 @@ enum {
   FLUID_DOMAIN_FIELD_FORCE_X = 11,
   FLUID_DOMAIN_FIELD_FORCE_Y = 12,
   FLUID_DOMAIN_FIELD_FORCE_Z = 13,
+  FLUID_DOMAIN_FIELD_PHI = 14,
+  FLUID_DOMAIN_FIELD_PHI_IN = 15,
+  FLUID_DOMAIN_FIELD_PHI_OUT = 16,
+  FLUID_DOMAIN_FIELD_PHI_OBSTACLE = 17,
+  FLUID_DOMAIN_FIELD_FLAGS = 18,
+  FLUID_DOMAIN_FIELD_PRESSURE = 19,
+};
+
+/* Fluid gridline display color field types. */
+enum {
+  FLUID_GRIDLINE_COLOR_TYPE_FLAGS = 1,
+  FLUID_GRIDLINE_COLOR_TYPE_RANGE = 2,
+};
+
+/* Fluid cell types.  */
+enum {
+  FLUID_CELL_TYPE_NONE = 0,
+  FLUID_CELL_TYPE_FLUID = (1 << 0),
+  FLUID_CELL_TYPE_OBSTACLE = (1 << 1),
+  FLUID_CELL_TYPE_EMPTY = (1 << 2),
+  FLUID_CELL_TYPE_INFLOW = (1 << 3),
+  FLUID_CELL_TYPE_OUTFLOW = (1 << 4),
 };
 
 /* Fluid domain types. */
@@ -446,6 +477,8 @@ typedef struct FluidDomainSettings {
   struct GPUTexture *tex_velocity_x;
   struct GPUTexture *tex_velocity_y;
   struct GPUTexture *tex_velocity_z;
+  struct GPUTexture *tex_flags;
+  struct GPUTexture *tex_range_field;
   struct Object *guide_parent;
   /** Vertex velocities of simulated fluid mesh. */
   struct FluidDomainVertexVelocity *mesh_velocities;
@@ -605,29 +638,41 @@ typedef struct FluidDomainSettings {
   int timesteps_maximum;
 
   /* Display options. */
-  char slice_method, axis_slice_method;
-  char slice_axis, draw_velocity;
   float slice_per_voxel;
   float slice_depth;
   float display_thickness;
+  float grid_scale;
   struct ColorBand *coba;
   float vector_scale;
+  float gridlines_lower_bound;
+  float gridlines_upper_bound;
+  float gridlines_range_color[4];
+  char axis_slice_method;
+  char slice_axis;
+  char show_gridlines;
+  char draw_velocity;
   char vector_draw_type;
+  char vector_field; /* Simulation field used for vector display. */
+  char vector_scale_with_magnitude;
+  char vector_draw_mac_components;
   char use_coba;
   char coba_field; /* Simulation field used for the color mapping. */
   char interp_method;
+  char gridlines_color_field; /* Simulation field used to color map onto gridlines. */
+  char gridlines_cell_filter;
+  char _pad9[7];
 
   /* OpenVDB cache options. */
   int openvdb_compression;
   float clipping;
   char openvdb_data_depth;
-  char _pad9[7]; /* Unused. */
+  char _pad10[7]; /* Unused. */
 
   /* -- Deprecated / unsed options (below). -- */
 
   /* View options. */
   int viewsettings;
-  char _pad10[4]; /* Unused. */
+  char _pad11[4]; /* Unused. */
 
   /* Pointcache options. */
   /* Smoke uses only one cache from now on (index [0]), but keeping the array for now for reading
@@ -637,7 +682,7 @@ typedef struct FluidDomainSettings {
   int cache_comp;
   int cache_high_comp;
   char cache_file_format;
-  char _pad11[7]; /* Unused. */
+  char _pad12[7]; /* Unused. */
 
 } FluidDomainSettings;
 
diff --git a/source/blender/makesdna/DNA_volume_defaults.h b/source/blender/makesdna/DNA_volume_defaults.h
index 8239f263c6c..a710754659b 100644
--- a/source/blender/makesdna/DNA_volume_defaults.h
+++ b/source/blender/makesdna/DNA_volume_defaults.h
@@ -32,6 +32,7 @@
     .density = 1.0f, \
     .wireframe_type = VOLUME_WIREFRAME_BOXES, \
     .wireframe_detail = VOLUME_WIREFRAME_COARSE, \
+    .slice_depth = 0.5f, \
   }
 
 #define _DNA_DEFAULT_VolumeRender \
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