Fluid: Added new viscosity solver

Mainly updated the Mantaflow version. It includes the new viscosity solver plugin based on the method from 'Accurate Viscous Free Surfaces for Buckling, Coiling, and Rotating Liquids' (Batty & Bridson).

In the UI, this update adds a new 'Viscosity' section to the fluid modifier UI (liquid domains only). For now, there is a single 'strength' value to control the viscosity of liquids.

7 files changed, 89 insertions, 45 deletions

diff --git a/source/blender/blenkernel/BKE_blender_version.h b/source/blender/blenkernel/BKE_blender_version.h
index 1ed4d1183a1..06a11fc8d1d 100644
--- a/source/blender/blenkernel/BKE_blender_version.h
+++ b/source/blender/blenkernel/BKE_blender_version.h
@@ -39,7 +39,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 8
+#define BLENDER_FILE_SUBVERSION 9
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and show a warning if the file
diff --git a/source/blender/blenkernel/intern/fluid.c b/source/blender/blenkernel/intern/fluid.c
index 1bdc2a5dfd2..b93e6148b86 100644
--- a/source/blender/blenkernel/intern/fluid.c
+++ b/source/blender/blenkernel/intern/fluid.c
@@ -5011,6 +5011,9 @@ void BKE_fluid_modifier_copy(const struct FluidModifierData *fmd,
     tfds->sys_particle_maximum = fds->sys_particle_maximum;
     tfds->simulation_method = fds->simulation_method;
 
+    /* viscosity options */
+    tfds->viscosity_value = fds->viscosity_value;
+
     /* diffusion options*/
     tfds->surface_tension = fds->surface_tension;
     tfds->viscosity_base = fds->viscosity_base;
diff --git a/source/blender/blenloader/intern/versioning_290.c b/source/blender/blenloader/intern/versioning_290.c
index 8a85278a931..63ef436d8e2 100644
--- a/source/blender/blenloader/intern/versioning_290.c
+++ b/source/blender/blenloader/intern/versioning_290.c
@@ -1430,18 +1430,7 @@ void blo_do_versions_290(FileData *fd, Library *UNUSED(lib), Main *bmain)
     }
   }
 
-  /**
-   * Versioning code until next subversion bump goes here.
-   *
-   * \note Be sure to check when bumping the version:
-   * - "versioning_userdef.c", #blo_do_versions_userdef
-   * - "versioning_userdef.c", #do_versions_theme
-   *
-   * \note Keep this message at the bottom of the function.
-   */
-  {
-    /* Keep this block, even when empty. */
-
+  if (!MAIN_VERSION_ATLEAST(bmain, 292, 9)) {
     FOREACH_NODETREE_BEGIN (bmain, ntree, id) {
       if (ntree->type == NTREE_GEOMETRY) {
         LISTBASE_FOREACH (bNode *, node, &ntree->nodes) {
@@ -1474,5 +1463,32 @@ void blo_do_versions_290(FileData *fd, Library *UNUSED(lib), Main *bmain)
         }
       }
     }
+
+    /* Ensure that new viscosity strength field is initialized correctly. */
+    if (!DNA_struct_elem_find(fd->filesdna, "FluidModifierData", "float", "viscosity_value")) {
+      LISTBASE_FOREACH (Object *, ob, &bmain->objects) {
+        LISTBASE_FOREACH (ModifierData *, md, &ob->modifiers) {
+          if (md->type == eModifierType_Fluid) {
+            FluidModifierData *fmd = (FluidModifierData *)md;
+            if (fmd->domain != NULL) {
+              fmd->domain->viscosity_value = 0.05;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  /**
+   * Versioning code until next subversion bump goes here.
+   *
+   * \note Be sure to check when bumping the version:
+   * - "versioning_userdef.c", #blo_do_versions_userdef
+   * - "versioning_userdef.c", #do_versions_theme
+   *
+   * \note Keep this message at the bottom of the function.
+   */
+  {
+    /* Keep this block, even when empty. */
   }
 }
diff --git a/source/blender/blenloader/intern/versioning_userdef.c b/source/blender/blenloader/intern/versioning_userdef.c
index f1572c563bf..b9f09e0326d 100644
--- a/source/blender/blenloader/intern/versioning_userdef.c
+++ b/source/blender/blenloader/intern/versioning_userdef.c
@@ -820,6 +820,12 @@ void blo_do_versions_userdef(UserDef *userdef)
     userdef->uiflag &= ~USER_UIFLAG_UNUSED_3;
   }
 
+  if (!USER_VERSION_ATLEAST(292, 9)) {
+    if (BLI_listbase_is_empty(&userdef->asset_libraries)) {
+      BKE_preferences_asset_library_default_add(userdef);
+    }
+  }
+
   /**
    * Versioning code until next subversion bump goes here.
    *
@@ -831,9 +837,6 @@ void blo_do_versions_userdef(UserDef *userdef)
    */
   {
     /* Keep this block, even when empty. */
-    if (BLI_listbase_is_empty(&userdef->asset_libraries)) {
-      BKE_preferences_asset_library_default_add(userdef);
-    }
   }
 
   LISTBASE_FOREACH (bTheme *, btheme, &userdef->themes) {
diff --git a/source/blender/makesdna/DNA_fluid_defaults.h b/source/blender/makesdna/DNA_fluid_defaults.h
index 2ee83cf3387..9454342654c 100644
--- a/source/blender/makesdna/DNA_fluid_defaults.h
+++ b/source/blender/makesdna/DNA_fluid_defaults.h
@@ -113,6 +113,7 @@
     .flip_ratio = 0.97f, \
     .sys_particle_maximum = 0, \
     .simulation_method = FLUID_DOMAIN_METHOD_FLIP, \
+    .viscosity_value = 0.05f, \
     .surface_tension = 0.0f, \
     .viscosity_base = 1.0f, \
     .viscosity_exponent = 6.0f, \
diff --git a/source/blender/makesdna/DNA_fluid_types.h b/source/blender/makesdna/DNA_fluid_types.h
index 98007a2b0b1..2ba0d15fbb3 100644
--- a/source/blender/makesdna/DNA_fluid_types.h
+++ b/source/blender/makesdna/DNA_fluid_types.h
@@ -52,6 +52,7 @@ enum {
   FLUID_DOMAIN_DELETE_IN_OBSTACLE = (1 << 14),  /* Delete fluid inside obstacles. */
   FLUID_DOMAIN_USE_DIFFUSION = (1 << 15), /* Use diffusion (e.g. viscosity, surface tension). */
   FLUID_DOMAIN_USE_RESUMABLE_CACHE = (1 << 16), /* Determine if cache should be resumable. */
+  FLUID_DOMAIN_USE_VISCOSITY = (1 << 17),       /* Use viscosity. */
 };
 
 /**
@@ -289,7 +290,7 @@ enum {
 #define FLUID_NAME_GUIDING "fluid_guiding"
 
 /* Fluid object names.*/
-#define FLUID_NAME_FLAGS "flags"       /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_FLAGS "flags" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_VELOCITY "velocity" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_VEL "vel"
 #define FLUID_NAME_VELOCITYTMP "velocity_previous" /* == OpenVDB grid attribute name. */
@@ -300,7 +301,7 @@ enum {
 #define FLUID_NAME_PHIOBS "phi_obstacle" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_PHISIN "phiSIn"
 #define FLUID_NAME_PHIIN "phi_inflow" /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_PHIOUT "phi_out"   /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_PHIOUT "phi_out" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_FORCES "forces"
 #define FLUID_NAME_FORCE_X "x_force"
 #define FLUID_NAME_FORCE_Y "y_force"
@@ -322,37 +323,37 @@ enum {
 #define FLUID_NAME_PHIOUTIN "phi_out_inflow"
 
 /* Smoke object names. */
-#define FLUID_NAME_SHADOW "shadow"     /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_SHADOW "shadow" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_EMISSION "emission" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_EMISSIONIN "emissionIn"
-#define FLUID_NAME_DENSITY "density"          /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_DENSITY "density" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_DENSITYIN "density_inflow" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_HEAT "heat"
 #define FLUID_NAME_HEATIN "heatIn"
-#define FLUID_NAME_TEMPERATURE "temperature"          /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_TEMPERATURE "temperature" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_TEMPERATUREIN "temperature_inflow" /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_COLORR "color_r"                   /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_COLORG "color_g"                   /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_COLORB "color_b"                   /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_COLORRIN "color_r_inflow"          /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_COLORGIN "color_g_inflow"          /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_COLORBIN "color_b_inflow"          /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_FLAME "flame"                      /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_FUEL "fuel"                        /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_REACT "react"                      /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_FUELIN "fuel_inflow"               /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_REACTIN "react_inflow"             /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_COLORR "color_r" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_COLORG "color_g" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_COLORB "color_b" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_COLORRIN "color_r_inflow" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_COLORGIN "color_g_inflow" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_COLORBIN "color_b_inflow" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_FLAME "flame" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_FUEL "fuel" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_REACT "react" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_FUELIN "fuel_inflow" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_REACTIN "react_inflow" /* == OpenVDB grid attribute name. */
 
 /* Liquid object names. */
 #define FLUID_NAME_PHIPARTS "phi_particles" /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_PHI "phi"                /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_PHITMP "phi_previous"    /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_PHI "phi" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_PHITMP "phi_previous" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_VELOCITYOLD "velOld"
 #define FLUID_NAME_VELOCITYPARTS "velParts"
 #define FLUID_NAME_MAPWEIGHTS "mapWeights"
 #define FLUID_NAME_PP "pp"
 #define FLUID_NAME_PVEL "pVel"
-#define FLUID_NAME_PARTS "particles"                  /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_PARTS "particles" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_PARTSVELOCITY "particles_velocity" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_PINDEX "pindex"
 #define FLUID_NAME_GPI "gpi"
@@ -375,8 +376,8 @@ enum {
 #define FLUID_NAME_TEXTURE_U2 "textureU2"
 #define FLUID_NAME_TEXTURE_V2 "textureV2"
 #define FLUID_NAME_TEXTURE_W2 "textureW2"
-#define FLUID_NAME_UV0 "uv_grid_0"              /* == OpenVDB grid attribute name. */
-#define FLUID_NAME_UV1 "uv_grid_1"              /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_UV0 "uv_grid_0" /* == OpenVDB grid attribute name. */
+#define FLUID_NAME_UV1 "uv_grid_1" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_COLORR_NOISE "color_r_noise" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_COLORG_NOISE "color_g_noise" /* == OpenVDB grid attribute name. */
 #define FLUID_NAME_COLORB_NOISE "color_b_noise" /* == OpenVDB grid attribute name. */
@@ -596,6 +597,10 @@ typedef struct FluidDomainSettings {
   short simulation_method;
   char _pad4[6];
 
+  /* Viscosity options. */
+  float viscosity_value;
+  char _pad5[4];
+
   /* Diffusion options. */
   float surface_tension;
   float viscosity_base;
@@ -610,7 +615,7 @@ typedef struct FluidDomainSettings {
   int mesh_scale;
   int totvert;
   short mesh_generator;
-  char _pad5[6]; /* Unused. */
+  char _pad6[6]; /* Unused. */
 
   /* Secondary particle options. */
   int particle_type;
@@ -631,7 +636,7 @@ typedef struct FluidDomainSettings {
   int sndparticle_update_radius;
   char sndparticle_boundary;
   char sndparticle_combined_export;
-  char _pad6[6]; /* Unused. */
+  char _pad7[6]; /* Unused. */
 
   /* Fluid guiding options. */
   float guide_alpha;      /* Guiding weight scalar (determines strength). */
@@ -639,7 +644,7 @@ typedef struct FluidDomainSettings {
   float guide_vel_factor; /* Multiply guiding velocity by this factor. */
   int guide_res[3];       /* Res for velocity guide grids - independent from base res. */
   short guide_source;
-  char _pad7[2]; /* Unused. */
+  char _pad8[2]; /* Unused. */
 
   /* Cache options. */
   int cache_frame_start;
@@ -659,7 +664,7 @@ typedef struct FluidDomainSettings {
   char error[64]; /* Bake error description. */
   short cache_type;
   char cache_id[4]; /* Run-time only */
-  char _pad8[2];
+  char _pad9[2];    /* Unused. */
 
   /* Time options. */
   float dt;
@@ -694,19 +699,19 @@ typedef struct FluidDomainSettings {
   char interp_method;
   char gridlines_color_field; /* Simulation field used to color map onto gridlines. */
   char gridlines_cell_filter;
-  char _pad9[7];
+  char _pad10[7]; /* Unused. */
 
   /* OpenVDB cache options. */
   int openvdb_compression;
   float clipping;
   char openvdb_data_depth;
-  char _pad10[7]; /* Unused. */
+  char _pad11[7]; /* Unused. */
 
   /* -- Deprecated / unsed options (below). -- */
 
   /* View options. */
   int viewsettings;
-  char _pad11[4]; /* Unused. */
+  char _pad12[4]; /* Unused. */
 
   /* Pointcache options. */
   /* Smoke uses only one cache from now on (index [0]), but keeping the array for now for reading
@@ -716,7 +721,7 @@ typedef struct FluidDomainSettings {
   int cache_comp;
   int cache_high_comp;
   char cache_file_format;
-  char _pad12[7]; /* Unused. */
+  char _pad13[7]; /* Unused. */
 
 } FluidDomainSettings;
 
diff --git a/source/blender/makesrna/intern/rna_fluid.c b/source/blender/makesrna/intern/rna_fluid.c
index bb8280ede91..afe564dff0a 100644
--- a/source/blender/makesrna/intern/rna_fluid.c
+++ b/source/blender/makesrna/intern/rna_fluid.c
@@ -1929,6 +1929,22 @@ static void rna_def_fluid_domain_settings(BlenderRNA *brna)
       "Maximum number of fluid particles that are allowed in this simulation");
   RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_Fluid_datacache_reset");
 
+  /* viscosity options */
+
+  prop = RNA_def_property(srna, "use_viscosity", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flags", FLUID_DOMAIN_USE_VISCOSITY);
+  RNA_def_property_ui_text(prop, "Use Viscosity", "Enable fluid viscosity settings");
+  RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_Fluid_datacache_reset");
+
+  prop = RNA_def_property(srna, "viscosity_value", PROP_FLOAT, PROP_NONE);
+  RNA_def_property_range(prop, 0.0, 10.0);
+  RNA_def_property_ui_range(prop, 0.0, 5.0, 0.01, 3);
+  RNA_def_property_ui_text(prop,
+                           "Strength",
+                           "Viscosity of liquid (higher values result in more viscous fluids, a "
+                           "value of 0 will still apply some viscosity)");
+  RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_Fluid_datacache_reset");
+
   /*  diffusion options */
 
   prop = RNA_def_property(srna, "use_diffusion", PROP_BOOLEAN, PROP_NONE);