Fluid: Added offset to control frame range

Added an offset field to control when to load the simulation files. Since this is a very small but helpful addition it is in my view safe to commit at this point of the bcon cycle.

release/scripts/startup/bl_ui/properties_physics_fluid.py

@@ -1135,22 +1135,22 @@ class PHYSICS_PT_cache(PhysicButtonsPanel, Panel):
         flow = layout.grid_flow(row_major=True, columns=0, even_columns=True, even_rows=False, align=False)
 
         col = flow.column()
-        col.prop(domain, "cache_type", expand=False)
-        col.enabled = not is_baking_any
-
-        col.separator()
-
         row = col.row()
-        col = row.column(align=True)
-        col.prop(domain, "cache_frame_start", text="Frame Start")
-        col.prop(domain, "cache_frame_end", text="End")
-        row.enabled = not is_baking_any
+        row = row.column(align=True)
+        row.prop(domain, "cache_frame_start", text="Frame Start")
+        row.prop(domain, "cache_frame_end", text="End")
+        row = col.row()
+        row.enabled = domain.cache_type in {'MODULAR', 'ALL'}
+        row.prop(domain, "cache_frame_offset", text="Offset")
 
         col.separator()
 
         col = flow.column()
-        col.enabled = not is_baking_any and not has_baked_data
-        col.prop(domain, "cache_resumable", text="Is Resumable")
+        col.prop(domain, "cache_type", expand=False)
+
+        row = col.row()
+        row.enabled = not is_baking_any and not has_baked_data
+        row.prop(domain, "cache_resumable", text="Is Resumable")
 
         row = col.row()
         row.enabled = not is_baking_any and not has_baked_data

source/blender/blenkernel/intern/fluid.c

@@ -3724,10 +3724,31 @@ static void BKE_fluid_modifier_processDomain(FluidModifierData *mmd,
   bool is_startframe, has_advanced;
   is_startframe = (scene_framenr == mds->cache_frame_start);
   has_advanced = (scene_framenr == mmd->time + 1);
+  int mode = mds->cache_type;
 
   /* Do not process modifier if current frame is out of cache range. */
-  if (scene_framenr < mds->cache_frame_start || scene_framenr > mds->cache_frame_end) {
-    return;
+  switch (mode) {
+    case FLUID_DOMAIN_CACHE_ALL:
+    case FLUID_DOMAIN_CACHE_MODULAR:
+      if (mds->cache_frame_offset > 0) {
+        if (scene_framenr < mds->cache_frame_start ||
+            scene_framenr > mds->cache_frame_end + mds->cache_frame_offset) {
+          return;
+        }
+      }
+      else {
+        if (scene_framenr < mds->cache_frame_start + mds->cache_frame_offset ||
+            scene_framenr > mds->cache_frame_end) {
+          return;
+        }
+      }
+      break;
+    case FLUID_DOMAIN_CACHE_REPLAY:
+    default:
+      if (scene_framenr < mds->cache_frame_start || scene_framenr > mds->cache_frame_end) {
+        return;
+      }
+      break;
   }
 
   /* Reset fluid if no fluid present. Also resets active fields. */
@@ -3865,7 +3886,6 @@ static void BKE_fluid_modifier_processDomain(FluidModifierData *mmd,
   with_gdomain = (mds->guide_source == FLUID_DOMAIN_GUIDE_SRC_DOMAIN);
 
   int o_res[3], o_min[3], o_max[3], o_shift[3];
-  int mode = mds->cache_type;
 
   /* Cache mode specific settings. */
   switch (mode) {
@@ -3875,6 +3895,12 @@ static void BKE_fluid_modifier_processDomain(FluidModifierData *mmd,
       if (!baking_data && !baking_noise && !baking_mesh && !baking_particles && !baking_guide) {
         read_cache = true;
         bake_cache = false;
+
+        /* Apply frame offset. */
+        data_frame -= mmd->domain->cache_frame_offset;
+        noise_frame -= mmd->domain->cache_frame_offset;
+        mesh_frame -= mmd->domain->cache_frame_offset;
+        particles_frame -= mmd->domain->cache_frame_offset;
         break;
       }
 
@@ -4905,6 +4931,7 @@ void BKE_fluid_modifier_create_type_data(struct FluidModifierData *mmd)
     mmd->domain->cache_frame_pause_mesh = 0;
     mmd->domain->cache_frame_pause_particles = 0;
     mmd->domain->cache_frame_pause_guide = 0;
+    mmd->domain->cache_frame_offset = 0;
     mmd->domain->cache_flag = 0;
     mmd->domain->cache_type = FLUID_DOMAIN_CACHE_REPLAY;
     mmd->domain->cache_mesh_format = FLUID_DOMAIN_FILE_BIN_OBJECT;
@@ -5151,6 +5178,7 @@ void BKE_fluid_modifier_copy(const struct FluidModifierData *mmd,
     tmds->cache_frame_pause_mesh = mds->cache_frame_pause_mesh;
     tmds->cache_frame_pause_particles = mds->cache_frame_pause_particles;
     tmds->cache_frame_pause_guide = mds->cache_frame_pause_guide;
+    tmds->cache_frame_offset = mds->cache_frame_offset;
     tmds->cache_flag = mds->cache_flag;
     tmds->cache_type = mds->cache_type;
     tmds->cache_mesh_format = mds->cache_mesh_format;

source/blender/makesdna/DNA_fluid_types.h

@@ -580,6 +580,7 @@ typedef struct FluidDomainSettings {
   int cache_frame_pause_mesh;
   int cache_frame_pause_particles;
   int cache_frame_pause_guide;
+  int cache_frame_offset;
   int cache_flag;
   char cache_mesh_format;
   char cache_data_format;
@@ -589,7 +590,7 @@ typedef struct FluidDomainSettings {
   char error[64]; /* Bake error description. */
   short cache_type;
   char cache_id[4]; /* Run-time only */
-  char _pad8[6];
+  char _pad8[2];
 
   /* Time options. */
   float dt;

source/blender/makesrna/intern/rna_fluid.c

@@ -2002,13 +2002,28 @@ static void rna_def_fluid_domain_settings(BlenderRNA *brna)
   RNA_def_property_int_sdna(prop, NULL, "cache_frame_start");
   RNA_def_property_range(prop, -MAXFRAME, MAXFRAME);
   RNA_def_property_int_funcs(prop, NULL, "rna_Fluid_cache_startframe_set", NULL);
-  RNA_def_property_ui_text(prop, "Start", "Frame on which the simulation starts");
+  RNA_def_property_ui_text(
+      prop,
+      "Start",
+      "Frame on which the simulation starts. This is the first frame that will be baked");
 
   prop = RNA_def_property(srna, "cache_frame_end", PROP_INT, PROP_TIME);
   RNA_def_property_int_sdna(prop, NULL, "cache_frame_end");
   RNA_def_property_range(prop, -MAXFRAME, MAXFRAME);
   RNA_def_property_int_funcs(prop, NULL, "rna_Fluid_cache_endframe_set", NULL);
-  RNA_def_property_ui_text(prop, "End", "Frame on which the simulation stops");
+  RNA_def_property_ui_text(
+      prop,
+      "End",
+      "Frame on which the simulation stops. This is the last frame that will be baked");
+
+  prop = RNA_def_property(srna, "cache_frame_offset", PROP_INT, PROP_TIME);
+  RNA_def_property_int_sdna(prop, NULL, "cache_frame_offset");
+  RNA_def_property_range(prop, -MAXFRAME, MAXFRAME);
+  RNA_def_property_ui_text(
+      prop,
+      "Offset",
+      "Frame offset that is used when loading the simulation from the cache. It is not considered "
+      "when baking the simulation, only when loading it");
 
   prop = RNA_def_property(srna, "cache_frame_pause_data", PROP_INT, PROP_TIME);
   RNA_def_property_int_sdna(prop, NULL, "cache_frame_pause_data");