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, 4 insertions, 2 deletions

diff --git a/source/blender/draw/engines/workbench/workbench_engine.c b/source/blender/draw/engines/workbench/workbench_engine.c
index 80a8f310191..ed9cb17ae28 100644
--- a/source/blender/draw/engines/workbench/workbench_engine.c
+++ b/source/blender/draw/engines/workbench/workbench_engine.c
@@ -367,9 +367,11 @@ void workbench_cache_populate(void *ved, Object *ob)
     ModifierData *md = BKE_modifiers_findby_type(ob, eModifierType_Fluid);
     if (md && BKE_modifier_is_enabled(wpd->scene, md, eModifierMode_Realtime)) {
       FluidModifierData *fmd = (FluidModifierData *)md;
-      if (fmd->domain && fmd->domain->type == FLUID_DOMAIN_TYPE_GAS) {
+      if (fmd->domain) {
         workbench_volume_cache_populate(vedata, wpd->scene, ob, md, V3D_SHADING_SINGLE_COLOR);
-        return; /* Do not draw solid in this case. */
+        if (fmd->domain->type == FLUID_DOMAIN_TYPE_GAS) {
+          return; /* Do not draw solid in this case. */
+        }
       }
     }
   }