Fluid: Fix for issues with external forces

A general refactor / fix commit that should clear out the issues that have been reported on external forces and moving effectors (e.g. T79537, T81660, T80088).

intern/mantaflow/intern/strings/fluid_script.h

@@ -122,7 +122,6 @@ timePerFrame_s$ID$ = $TIME_PER_FRAME$\n\
 # In Blender fluid.c: frame_length = DT_DEFAULT * (25.0 / fps) * time_scale\n\
 # with DT_DEFAULT = 0.1\n\
 frameLength_s$ID$ = $FRAME_LENGTH$\n\
-frameLengthUnscaled_s$ID$  = frameLength_s$ID$ / timeScale_s$ID$\n\
 frameLengthRaw_s$ID$ = 0.1 * 25 # dt = 0.1 at 25 fps\n\
 \n\
 dt0_s$ID$          = $DT$\n\
@@ -149,18 +148,9 @@ mantaMsg('1 Blender length unit is ' + str(ratioResToBLength_s$ID$) + ' Mantaflo
 ratioBTimeToTimestep_s$ID$ = float(1) / float(frameLengthRaw_s$ID$) # the time within 1 blender time unit, see also fluid.c\n\
 mantaMsg('1 Blender time unit is ' + str(ratioBTimeToTimestep_s$ID$) + ' Mantaflow time units long.')\n\
 \n\
-ratioFrameToFramelength_s$ID$ = float(1) / float(frameLengthUnscaled_s$ID$ ) # the time within 1 frame\n\
-mantaMsg('frame / frameLength is ' + str(ratioFrameToFramelength_s$ID$) + ' Mantaflow time units long.')\n\
-\n\
 scaleAcceleration_s$ID$ = ratioResToBLength_s$ID$ * (ratioBTimeToTimestep_s$ID$**2)# [meters/btime^2] to [cells/timestep^2] (btime: sec, min, or h, ...)\n\
 mantaMsg('scaleAcceleration is ' + str(scaleAcceleration_s$ID$))\n\
 \n\
-scaleSpeedFrames_s$ID$ = ratioResToBLength_s$ID$ * ratioFrameToFramelength_s$ID$ # [blength/frame] to [cells/frameLength]\n\
-mantaMsg('scaleSpeed is ' + str(scaleSpeedFrames_s$ID$))\n\
-\n\
-scaleSpeedTime_s$ID$ = ratioResToBLength_s$ID$ * ratioBTimeToTimestep_s$ID$ # [blength/btime] to [cells/frameLength]\n\
-mantaMsg('scaleSpeedTime is ' + str(scaleSpeedTime_s$ID$))\n\
-\n\
 gravity_s$ID$ *= scaleAcceleration_s$ID$ # scale from world acceleration to cell based acceleration\n\
 \n\
 # OpenVDB options\n\
@@ -380,17 +370,10 @@ def fluid_pre_step_$ID$():\n\
         x_obvel_s$ID$.safeDivide(numObs_s$ID$)\n\
         y_obvel_s$ID$.safeDivide(numObs_s$ID$)\n\
         z_obvel_s$ID$.safeDivide(numObs_s$ID$)\n\
-        \n\
-        x_obvel_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
-        y_obvel_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
-        z_obvel_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
         copyRealToVec3(sourceX=x_obvel_s$ID$, sourceY=y_obvel_s$ID$, sourceZ=z_obvel_s$ID$, target=obvelC_s$ID$)\n\
     \n\
     # translate invels (world space) to grid space\n\
     if using_invel_s$ID$:\n\
-        x_invel_s$ID$.multConst(scaleSpeedTime_s$ID$)\n\
-        y_invel_s$ID$.multConst(scaleSpeedTime_s$ID$)\n\
-        z_invel_s$ID$.multConst(scaleSpeedTime_s$ID$)\n\
         copyRealToVec3(sourceX=x_invel_s$ID$, sourceY=y_invel_s$ID$, sourceZ=z_invel_s$ID$, target=invelC_s$ID$)\n\
     \n\
     if using_guiding_s$ID$:\n\
@@ -400,9 +383,6 @@ def fluid_pre_step_$ID$():\n\
         velT_s$ID$.multConst(vec3(gamma_sg$ID$))\n\
     \n\
     # translate external forces (world space) to grid space\n\
-    x_force_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
-    y_force_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
-    z_force_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
     copyRealToVec3(sourceX=x_force_s$ID$, sourceY=y_force_s$ID$, sourceZ=z_force_s$ID$, target=forces_s$ID$)\n\
     \n\
     # If obstacle has velocity, i.e. is a moving obstacle, switch to dynamic preconditioner\n\
@@ -626,10 +606,6 @@ def bake_guiding_process_$ID$(framenr, format_guiding, path_guiding, resumable):
     x_guidevel_s$ID$.safeDivide(numGuides_s$ID$)\n\
     y_guidevel_s$ID$.safeDivide(numGuides_s$ID$)\n\
     z_guidevel_s$ID$.safeDivide(numGuides_s$ID$)\n\
-    \n\
-    x_guidevel_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
-    y_guidevel_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
-    z_guidevel_s$ID$.multConst(scaleSpeedFrames_s$ID$)\n\
     copyRealToVec3(sourceX=x_guidevel_s$ID$, sourceY=y_guidevel_s$ID$, sourceZ=z_guidevel_s$ID$, target=guidevelC_s$ID$)\n\
     \n\
     mantaMsg('Extrapolating guiding velocity')\n\

source/blender/blenkernel/intern/fluid.c

@@ -925,7 +925,7 @@ static void update_velocities(FluidEffectorSettings *fes,
       velocity_map[index * 3 + 2] = hit_vel[2];
 #  ifdef DEBUG_PRINT
       /* Debugging: Print object velocities. */
-      printf("adding effector object vel: [%f, %f, %f]\n", hit_vel[0], hit_vel[1], hit_vel[2]);
+      printf("setting effector object vel: [%f, %f, %f]\n", hit_vel[0], hit_vel[1], hit_vel[2]);
 #  endif
     }
     else {
@@ -1065,7 +1065,7 @@ static void obstacles_from_mesh(Object *coll_ob,
       add_v3fl_v3fl_v3i(co, mvert[i].co, fds->shift);
       if (has_velocity) {
         sub_v3_v3v3(&vert_vel[i * 3], co, &fes->verts_old[i * 3]);
-        mul_v3_fl(&vert_vel[i * 3], fds->dx / dt);
+        mul_v3_fl(&vert_vel[i * 3], 1.0f / dt);
       }
       copy_v3_v3(&fes->verts_old[i * 3], co);
 
@@ -1824,6 +1824,7 @@ static void sample_mesh(FluidFlowSettings *ffs,
                         float *velocity_map,
                         int index,
                         const int base_res[3],
+                        const float global_size[3],
                         const float flow_center[3],
                         BVHTreeFromMesh *tree_data,
                         const float ray_start[3],
@@ -1983,9 +1984,23 @@ static void sample_mesh(FluidFlowSettings *ffs,
         printf("adding flow object vel: [%f, %f, %f]\n", hit_vel[0], hit_vel[1], hit_vel[2]);
 #  endif
       }
-      velocity_map[index * 3] += ffs->vel_coord[0];
-      velocity_map[index * 3 + 1] += ffs->vel_coord[1];
-      velocity_map[index * 3 + 2] += ffs->vel_coord[2];
+      /* Convert xyz velocities flow settings from world to grid space. */
+      float convert_vel[3];
+      copy_v3_v3(convert_vel, ffs->vel_coord);
+      float time_mult = 1.0 / (25.f * DT_DEFAULT);
+      float size_mult = MAX3(base_res[0], base_res[1], base_res[2]) /
+                        MAX3(global_size[0], global_size[1], global_size[2]);
+      mul_v3_v3fl(convert_vel, ffs->vel_coord, size_mult * time_mult);
+
+      velocity_map[index * 3] += convert_vel[0];
+      velocity_map[index * 3 + 1] += convert_vel[1];
+      velocity_map[index * 3 + 2] += convert_vel[2];
+#  ifdef DEBUG_PRINT
+      printf("initial vel: [%f, %f, %f]\n",
+             velocity_map[index * 3],
+             velocity_map[index * 3 + 1],
+             velocity_map[index * 3 + 2]);
+#  endif
     }
   }
 
@@ -2039,6 +2054,7 @@ static void emit_from_mesh_task_cb(void *__restrict userdata,
                     bb->velocity,
                     index,
                     data->fds->base_res,
+                    data->fds->global_size,
                     data->flow_center,
                     data->tree,
                     ray_start,
@@ -2136,7 +2152,7 @@ static void emit_from_mesh(
         add_v3fl_v3fl_v3i(co, mvert[i].co, fds->shift);
         if (has_velocity) {
           sub_v3_v3v3(&vert_vel[i * 3], co, &ffs->verts_old[i * 3]);
-          mul_v3_fl(&vert_vel[i * 3], fds->dx / dt);
+          mul_v3_fl(&vert_vel[i * 3], 1.0 / dt);
         }
         copy_v3_v3(&ffs->verts_old[i * 3], co);
       }
@@ -2434,19 +2450,6 @@ static void adaptive_domain_adjust(
     /* Redo adapt time step in manta to refresh solver state (ie time variables) */
     manta_adapt_timestep(fds->fluid);
   }
-
-  /* update global size field with new bbox size */
-  /* volume bounds */
-  float minf[3], maxf[3], size[3];
-  madd_v3fl_v3fl_v3fl_v3i(minf, fds->p0, fds->cell_size, fds->res_min);
-  madd_v3fl_v3fl_v3fl_v3i(maxf, fds->p0, fds->cell_size, fds->res_max);
-  /* calculate domain dimensions */
-  sub_v3_v3v3(size, maxf, minf);
-  /* apply object scale */
-  for (int i = 0; i < 3; i++) {
-    size[i] = fabsf(size[i] * ob->scale[i]);
-  }
-  copy_v3_v3(fds->global_size, size);
 }
 
 BLI_INLINE void apply_outflow_fields(int index,
@@ -4423,7 +4426,7 @@ float BKE_fluid_get_velocity_at(struct Object *ob, float position[3], float velo
     FluidDomainSettings *fds = fmd->domain;
     float time_mult = 25.f * DT_DEFAULT;
     float size_mult = MAX3(fds->global_size[0], fds->global_size[1], fds->global_size[2]) /
-                      fds->maxres;
+                      MAX3(fds->base_res[0], fds->base_res[1], fds->base_res[2]);
     float vel_mag;
     float density = 0.0f, fuel = 0.0f;
     float pos[3];

source/blender/makesrna/intern/rna_fluid.c

@@ -2781,7 +2781,9 @@ static void rna_def_fluid_flow_settings(BlenderRNA *brna)
   RNA_def_property_array(prop, 3);
   RNA_def_property_range(prop, -1000.1, 1000.1);
   RNA_def_property_ui_text(
-      prop, "Initial", "Initial velocity in X, Y and Z direction in world space");
+      prop,
+      "Initial",
+      "Additional initial velocity in X, Y and Z direction (added to source velocity)");
   RNA_def_property_update(prop, NC_OBJECT | ND_MODIFIER, "rna_Fluid_flow_reset");
 
   prop = RNA_def_property(srna, "volume_density", PROP_FLOAT, PROP_NONE);